Category Archives: Biology

Forensic Biology in Criminal Investigations

Question

Carl and Joseph were in the woods of Georgia in early fall. They had set up a camp because they were both deer hunters. In the fall of years when the weather is cooler, deer are very prevalent. On this cool November morning, the men were walking through the woods in their quest for deer. On the second day of being in the woods, walking through what was really thick brush and uneven terrain, one of the men slipped and fell into what appeared to be a covering of a hole in the ground. As he began to try and pull himself out, he saw several skulls and bones lying around. He immediately screamed for his friend, who assisted him in getting out of the hole. Together, they looked in and saw skeletons and what appeared to be a decomposing body.

The two men called the local police. The police arrived, secured the area, and called for the forensic team to come and investigate. You are the forensic person that has been asked to identify the 5 skeletons in the grave and the body that was only partially decomposed.

  •  Why will this particular case require the use of forensic biology? Explain in detail.
  •  When you arrive on the scene, what is your first course of action? Describe your process, and be specific.
  •  How will you avoid contamination at this stage of the investigation? Explain.
  •  How will you control the other first responders or law enforcement officers? What challenges do they pose to a forensic investigator? Explain.
  •  What will you do to identify the remains at this crime scene? Explain.
  • What is the documentation process for collecting and preserving this type of evidence? Explain.
  •  How will you transport your evidence to the lab safely? Explain.
  • Once you arrive back at the lab, what significant risks of contamination exist? Explain.
  •  How will you avoid this contamination? Explain.
  • What is the process for DNA analysis on the decomposing body?
  •  What specific tests will you use? Explain.
  • How will serology play a role in the selected testing processes? Explain.
  •  Using this decomposing body as an example, what is the process that you will follow to properly conduct this DNA test?
  •  What challenges or barriers exist when you begin to interpret the results of your DNA test? Explain in detail.
  •  How large of a role will facial reconstruction play in this investigation? Explain.
  •  Next, provide 2 scenarios of court case outcomes regarding this investigation.
  •   One scenario must result in the successful identification and conviction of the perpetrator. You will need to fill in the blanks with regard to physical evidence and other necessary details.
  • The other scenario must result in a wrongful conviction. You will need to identify the elements that lead to this wrongful conviction.

Sample paper

Forensic Biology in Criminal Investigations

Use of Forensic Biology

Forensic biology is one of the most reliable sources of crime scene evidence. The particular case will require forensic biology because it involves murder, which is a serious crime. All serious crimes attract hash punishments, which may involve spending an entire lifetime in prison (Kayser, 2017). Forensic biology will also be necessary because no human eyewitnesses are present to help solve the mysterious murders. Forensic biology will provide critical leads concerning the people who committed the murder. By examining the DNA evidence obtained from the crime scene, the law enforcement officials can be able to identify the suspects (Kayser, 2017). Identifying the suspects will require the law enforcement officials to match samples of possible suspects with those obtained from the crime scene. A non-match could be a strong indicator that the suspect was not involved.

The particular case will require forensic biology for the identification of crime victims. The case indicates that some bodies had undergone decomposition leaving skeletons while another was partially decomposed. It is not possible to prove the identity of the victims without the use of forensic biology, and in particular DNA matching. Matching DNA profiles of the crime victims with DNA profiles of people who have lost their loved ones under mysterious circumstances will help in establishing or excluding paternal relationship, and thus the identity of the victims (Kayser, 2017). It is highly possible that the crime scene contains DNA samples of the person who committed the crimes.

First Course of Action

On arriving at the scene, the first course of action will be to scan the surrounding area to ensure the safety of all officers. An initial observation of the crime scene can also help in assessing the safety of all responders. This is important for the safety of all those involved in the investigation. The second step would be to secure the crime scene. It is important to ensure that only a few persons involved in the case enter the crime scene to avoid contamination and alteration of evidence. Restricting movement of all those around the crime scene including law enforcement officers not involved in the case is critical. It will be possible to control people by using a law enforcement tape all around the crime scene. Law enforcement officers may help in preventing people from getting across the law enforcement tape. The third step is to identify important people with regard to the scene, for instance, suspects and any witnesses. Law enforcement officers should handle suspects and witnesses. In addition, they should control family members and friends.

It is important to control the first responders or law enforcement officers. The first responding law enforcement officers should control people at the scene. For instance, they may secure and separate witnesses, suspects, family members, or bystanders. The law enforcement officers should prevent all those not essential to the investigation from the crime scene. This may include politicians, bystanders, and other law enforcement officers not connected to the case. The law enforcement officers should set up a wider physical barrier considering that it would be easier to reduce it compared to expanding. First responders and law enforcement officers pose a significant challenge in that they may interfere with or alter crime evidence. For instance, first responders may move key objects relating to the crime or even take away the evidence. Another risk is contamination of crime area. First responders who stray into the scene may shed DNA materials such as hair, skin, saliva, blood, and others, thus contaminating the scene.

Identifying the Remains

The first step in identifying the remains is to look for any physical evidence present at the scene, for instance, identification cards or any other documents. If there were no documents available, it would be important to conduct a forensic anthropology. A forensic anthropology involves the examination of crime scene remains to establish critical details such as the number of people, age, sex, cause of death, events following death, time of death, and among others (Dupras et al., 2016). The first step would be to identify whether all the skeletal remains are human or nonhuman. After this, it is important to determine the possible number of the victims. A biological profile of the bones can help reveal the sex, age at death, stature, and ancestry of the victims (Dupras et al., 2016). Studying skeletal modifications can help in telling how long the bodies have been there. Facial reconstruction using computer-aided techniques would also help in victim identification. After the skeletal profiling, it would be important to conduct nuclear DNA or mitochondrial profiling to narrow on the victims’ male relatives (Dupras et al., 2016).

The documentation process would first involve ensuring that the investigator has proper gear such as disposable shoe covers, hair net, eyeglasses, facemask, and body suit. Collecting and preserving the evidence would involve a number of steps or processes. First, there would be need to take photographs of every item at the scene of crime. The photographs should have scales for proper recording of each size of the item. The investigator can place a ruler at the scene when taking photographs in order to include accurate scales (Li, 2008). The investigator can also make detailed sketches of the scene. Another documentation process is the use of videography. A log sheet would help to note the chronological order of all photos taken (Li, 2008). It would be important to document the chain of custody when evidence transfers from one person to another. Search for particular evidence, for instance, identification documents, may be conducted once photographs are taken.

The investigator must collect small items from the scene in proper materials for presentation to a crime laboratory. The investigator should document any bloodstain pattern at the scene. In addition, he/she should collect any bloodstain at the scene. The investigator should collect both dry and wet samples, for instance, dry sexual fluids where possible (Li, 2008). The investigator should use forceps to collect pieces of hair from the scene. Where nails are available, the investigator may use clean clippers to obtain samples. Scrapping the nails may also provide samples. For bones, rib bones and vertebrae would offer the most evidence. The investigator may store dry bones in a container and freeze the wet bones. Porous materials such as paper are suitable for storing dry evidence (Li, 2008). The investigator should fold clothing with bloodstains carefully not to transfer evidence. The investigator must properly mark all evidence.

Transporting Evidence to the Lab Safely

The investigator should ensure evidence is safely stored in sealed containers or plastic bags to avoid contamination. It is important to ensure fragile items such as bones do not suffer damages during transportation (Li, 2008). The storage materials should protect the skeletons from exposure to heat and humidity since this may further damage the biological evidence. To avoid inadvertent damage to the bones during transportation, there would be sorting of bones and packing according to certain characteristics. For instance, the mandible, skull, pelvis, and all long bones should go in separate boxes to avoid damages during transportation. Placing the skull and pelvis together with other bones may cause damage hence making it difficult to obtain valuable clues. For instance, the skull may crush the cheekbones since they are very fragile. Packaging of bones and teeth in boxes can help prevent damage from external objects.

Each container or bag should have appropriate labels detailing the content, data, and investigator details. All arson debris should be transported using suitable jars or cans. Preferably, the storage containers should be previously unused. The investigator should cover the cans or jars with an aluminum foil and seal with a tape. This prevents contamination and further damage from heat and humidity. All boxes should be properly packed to avoid frequent shifting during transportation. Shifting may cause extensive damage to bones. The investigator should label clothes appropriately to avoid mix up. Wet clothes should be dried naturally.  Appropriate packaging materials in this crime scene would be envelopes, boxes, and bags (Li, 2008). Plastic bags may not be appropriate especially for evidence containing bloodstains. A body bag will help to transport the decomposing body. A plastic body bag will be appropriate for this work.

Significant Risks of Contamination at the Lab

Collected evidence faces a significant risk of contamination at the lab. Contamination issues may particularly arise in polymerase chain reactions (PCR). There are three major sources of contamination for PCRs. The first source of contamination is the lab environment (Carmona, 2009). A sample may obtain contamination from a genomic DNA in the laboratory environment, for instance, genomic DNA from a worker or a visitor. Secondly, two samples may inadvertently mix at microscopic or other levels leading to contamination (Carmona, 2009). This may particularly occur when DNA samples between two or more samples transfer during the preparation stages. Lastly, contamination may occur when the current sample mixes with amplified DNA samples from a previous polymerase chain reaction (Carmona, 2009). It is possible for a laboratory technician to carry DNA from post-PCRT reactions and contaminate new reagents.

Strictly adhering to outlined laboratory procedures can help in reducing or even eliminating the risk of contamination. It is possible to avoid contamination of samples by ensuring that pre-PCR and post-PCR amplification procedures are conducted is separate rooms (Carmona, 2009). Physical separation of these spaces would reduce the chances of carrying DNA from one test environment to another. Closely linked to this, the laboratory should have lab coats dedicated for each specific area. This would ensure that a lab technician does not move contaminants on his/her clothes from one area to another in the laboratory. It is also possible to avoid contamination by using disposable work gear, such as disposable caps, sleeves, and gloves (Carmona, 2009). Work gear offers a common source of contaminants. It is also possible to avoid contamination by ensuring thorough cleaning of all workplaces and equipment before and after working on the surfaces (Carmona, 2009). The laboratory technician should expose various reagents and material to ultra violet light.

The laboratory technician should work on amplifying a single item from a particular case. It is prudent to avoid amplifying items from multiple cases since this may contribute to a mix-up (Carmona, 2009). It is possible to monitor contamination by using reagent blanks and negative control procedures. This consists of samples having the different reagents used in the process, with the exemption of the template DNA. The PCR negative samples helps in detecting foreign DNA in the test environment (Carmona, 2009). The laboratory technician conducts the PCR negative tests using the same procedures and in the same environment with the PCR positive tests.

Process for DNA analysis on Decomposing Body

One may use a number of tests. If there are hardly bloodstains on the crime scene, it is important to conduct presumptive testing for blood (Mozayani & Noziglia, 2011). This may help in identifying materials that has blood irrespective of whether the blood is invisible to the naked eye. Another possible test is species testing blood. This involves antigen-antibody reaction using blood strain extracts. Species testing of blood may help determine whether all the blood strains are of human origin. Acid phosphate screening may help evaluate the possibility of seminal fluids on the body or cloths (Mozayani & Noziglia, 2011). Acid phosphate screening is inadequate as a lone test to confirm the presence of seminal fluids. The use of Brentamine test can help narrow down on non-stained areas that could be having seminal fluids. Items likely to contain spermatozoa may be further analyzed using a microscope. This may help to confirm the presence of spermatozoa.

Serology will play a critical role in the selected testing processes. Serology entails the identification and testing of different body fluids such as blood, saliva, urine, and seminal fluid. Serology analysis can help in identifying bodily fluids at the crime scene (Mozayani & Noziglia, 2011). For instance, serology may confirm the presence of seminal fluids in the crime scene and thus influence the testing process. Serology enables the forensic scientist to conduct presumptive and confirmatory tests on items. Presumptive tests helps in narrowing down on particular items in the crime scene. Presumptive tests confer the information that certain body fluids might be at the crime scene. The forensic scientist conducts more tests to confirm the presence of the body fluids.

One may use various processes to conduct DNA analysis on the decomposing body. A decomposing body would still have vast amount of DNA left. One of the possible tests is PCR-based STR. The DNA contains segments that have repetitive sequences. The sequences of repeats across individuals are significantly variable. Repeated segments are known as short tandem repeats (STRs) (Mozayani & Noziglia, 2011). The STRs can be critical in identification purposes. STR techniques are better compared with traditional techniques because they allow the researcher to use a small amount of DNA sample to obtain results. The STR technique is also quicker and accurate in evaluating of human DNA. STR technique can allow the researcher to establish the complete DNA profile for remains that had undergone severe decomposition or had exposure to extreme conditions.

There are certain challenges or barriers that come into play when interpreting the results of the DNA test. The first challenge relates to the matching of profiles for individuals, or in this case the skeletons and the evidence used (Mozayani & Noziglia, 2011). It is not possible to confirm a match since there exists the possibility that if other locations on the particular DNA are tested, they may yield different results indicating a non-match between the sample/evidence and the victim’s DNA profile. The accuracy of the STR analysis would therefore depend on how rare the alleles are and the number of loci examined (Mozayani & Noziglia, 2011). Another challenge is that the decomposing body may have two or more alleles on the same or different loci. Presence of two or more alleles could be an indicator that there was mixing of DNA. For the researcher to confirm the alleles, he/she must collect bodily fluid from the decomposing body’s actual fluids. Another challenge may arise when the DNA has varying intensity levels, meaning that the forensic scientist fails to identify all alleles. In such a case, it may not be possible to confirm whether a particular individual was present.

Role of Facial Reconstruction

Facial reconstruction will play a critical role in this investigation. Facial reconstruction can help in identification of victims when other methods fail to yield expected results. The use of modern software technology can allow forensic scientists to reproduce the facial features of an individual with a higher degree of certainty. With the reproduction of facial features, it becomes possible for friends or close family members to identify the victim. According to Gupta et al. (2015), the current improvements in 3D technology have led to a higher degree of accuracy in facial reproduction. The Manchester method has been particularly effective in the identification of individuals. Besides identification by family members and friends, facial reconstruction allows the forensic scientist to develop a list of possible victims (Gupta et al., 2015). The forensic scientist can them use multiple procedures to narrow down to a particular individual. As such, facial reconstruction will be critical in solving this case because most of the victims’ remains are only skeletal tissues.

Two Scenarios of Court Case Outcomes Regarding the Investigation

One of the possible scenarios is the successful identification of the perpetrator. This might be possible if the evidence available yields valuable clues leading to the arrest of the perpetrator. After combing through the crime scene, the forensic scientist discovered some pieces of undergarments believed to be from the decomposing body. A visual test using ultraviolet light was conducted to establish the presence of acid phosphatase. The test results were positive. Positive swabs of the clothing were then smeared on a slide and stained using red and green stain for visualization. Spermatozoa heads appeared red in color with blue-green tail. This confirmed the presence of spermatozoa on the decomposing body. DNA was extracted from the clothing and quantified using Short Tandem Repeat (STR) analysis. The DNA profile matched that of Craig David, a ‘jail bird’ who has been arrested on different occasions for various felonies such as drunk driving. Craig David is also suspected of a string of robberies in the area.

Another scenario in this case is a wrongful conviction. Craig David’s DNA matched 10 out of 13 alleles occurring in the DNA mixture not belonging to any of the victims. David named another suspect, Michael, whom he is believed to have a long time grudge as his accomplice in the murders. A DNA test revealed that Michael had two of the alleles being similar to those of the DNA mixture found at the scene of crime. The investigators concluded that Michael must have been an accomplice, although he vehemently denies this.

References

Carmona, R. (2009). Biology, conservation and sustainable development of sturgeons.      Dordrecht: Springer.

Dupras, T. L., Schultz, J. J., Wheeler, S. M., & Williams, L. J. (2016). Forensic recovery of         human remains: archaeological approaches, second edition. Boca Raton, Florida: CRC   Press.

Gupta, S., Gupta, V., Vij, H., Vij, R., & Tyagi, N. (2015). Forensic Facial Reconstruction: The    Final Frontier. Journal of Clinical and Diagnostic Research : JCDR9(9), ZE26–ZE28.             http://doi.org/10.7860/JCDR/2015/14621.6568

Kayser, M. (2017). Forensic use of Y-chromosome DNA: a general overview. Human      Genetics136(5), 621–635. http://doi.org/10.1007/s00439-017-1776-9

Li. R. (2008). Forensic biology: identification and DNA analysis of biological evidence. Boca      Raton, Florida: CRC Press.

Mozayani, A., & Noziglia, C. (2011). The Forensic Laboratory Handbook Procedures and          Practice [recurso electrónico]. Estados Unidos: Humana Press.

Related:

BIOL2269-MOLECULAR AGRICULTURE/ONPS-2083 MOLECULAR PLANT BREEDING

BIOL2269-MOLECULAR AGRICULTURE/ONPS-2083 MOLECULAR PLANT BREEDING

BIOL2269-MOLECULAR AGRICULTURE/ONPS-2083 MOLECULAR PLANT BREEDING

 

 

  1. Mean

For plant population A

For plant population B

Variance

For plant population A

 

For plant population B

A.

From the results of the variance in the population above, it is evident that population B is more genetically for height. The height of the difference plants tends to deviate more from the mean than in population A.

B.

If double haploids were used in the experiment it was expected that there could be no variation. This is because the genes in the plants chromosome both the right and left are identical and therefore the reproduced plants would have the characteristic height of the parent plant and hence no variations.

  1. Solution
  2. Total number of genes= 35+4+6+35 =80

Total number of recombinant = 4+6=10

Therefore, θ =0.125

 

Calculating the LOD

Probability that 10 plants out of the 80 are recombinants given that θ=0.125 is

The probability that the two loci are unlikened that θ=0.5; 40 recombinants and 40 non-recombinants plants is

B.

When the parental and recombinants are 350, 40,60 and 350

Total number of genes = 800

Total number of recombinants = 100

Calculating the LOD

Probability that 100 plants out of the 800 are recombinants given that θ=0.125 is

The probability that the two loci are unlikened that θ=0.5; 400 recombinants and 400 non-recombinants plants is

The LOD score is higher compared to the initial state hence showing a stronger statistical support.

Scenario: Heterochromatin absent, several marker loci homozygous

 

The genes are equally spaced on the chromosome and hence there is likeliness of crossover at any point of the chromosome.

Scenario: Heterochromatin present, several marker loci homozygous

The spacing of the genes is influenced by the presence of the heterochromatin; it ensures that the space between the genes in its position they get closely compact.

 

A.

In the first year when the experiment was begun it was expected that there would be less variation in the genes for resistance since crossing is expected and genes for non-resistance and resistance would cross and therefore being less effective. In the second season since this was a double haploid the genes would be more   identical and more resistant that is why higher QTL was detected in 2000.

The second season i.e. 2000 was the best year for assessing resistance since it is the year that the disease incidence in plants around the field site were higher. The climatic condition in the area in that year was also favorable for disease spread.

C.

In the first season the QTL outcome presented a scenario where by the plants were considered not to be effectively resistant, however in the coming year the outcome was higher and hence presented a situation whereby it was unpredictable whether there could be a different factor that may have contributed to the outcome.

Gene Therapy

Gene Therapy

Biological Basis

Technology has advanced in all areas and sectors including the medical field. New techniques have been designed in medicine to help improve healthcare services. One of these innovations is gene therapy. Gene therapy is a technique that makes use of genes to either prevent or treat a disease. This type of therapy involves transplantation of normal genes into the body cells with the purpose of treating genetic disorders or replacing missing genes. The gene transplanted is carefully selected in order to correct the effects caused by a mutated gene that causes disease.

There are two main types of gene therapy that are based on the cells being treated. One type is referred to as the Somatic gene therapy which involves the transfer of DNA to a body cell that does not produce eggs or sperms. This ensures that the patient’s children do not suffer the effects of the therapy. The other kind of therapy is the Germline gene therapy which is aimed at transferring the effects of the therapy to the patient’s offspring because the DNA is transferred to cells responsible for reproduction hence affects future generations (Wirth, 2013).

Gene therapy can be carried out in various techniques such as gene augmentation, gene inhibition and killing of particular cells. Augmentation type of therapy is used to treat mutation-caused diseases. In this therapy, functional DNA matching the lost gene is added back into the body cell. The new gene added produces enough protein to replace what was originally missing. However, this type of gene therapy is only effective if the disease has not completely damaged the body and can be reversed. On the other hand, gene inhibition technique is used in treatment of infectious or inherited diseases and cancer caused by incorrect gene activity. This technique is aimed at eliminating the gene activity that encourages growth of cells carrying the disease (Wirth, 2013). Killing of particular cells works by adding DNA into the disease-carrier cell that kills the cell hence stopping the disease.

Social and Ethical Implications behind Gene Therapy

Since gene therapy involves altering of the body’s DNA, it is bound to raise some ethical concerns among people. Most concerns fall on the germline type of gene therapy because it targets the reproductive cells. While this type of therapy may prevent future generations from suffering certain genetic disorders, it also has its effects. Research shows that germline therapy could have significant effects on the fetus and its development. It could be even worse when those effects are noticed way into the child’s development maybe even when they are already adults and can pass the same disorders to their children.

Errors caused by gene insertion can be fatal which has caused ethical issue because those receiving the gene are not yet even born hence do not get to have a say in a matter that could affect the rest of their lives. During research on germline therapy, if the disease to be treated is identified in a fetus, it complicates the issue which causes regular creation and destruction of embryos during research. This poses a social issue because it is basically murder of an unborn child. It may difficult for some people to understand why one should be implanted with a defective embryo only to later destroy it (Sade, 1998).

There are also social concerns related to gene therapy because of the involved costs. Although the technique may be effective in eliminating diseases such as cancer and function disorders such as cystic fibrosis, it may not be able to help many people. Gene therapy normally requires individual step-by-step approach which may be take a long time in hospitals conducting tests and other related procedures which may be very expensive. This means that the therapy can only help the wealthy who are able to pay for it leaving the less fortunate at a disadvantage. Medical breakthroughs are made with the aim of helping as many people as possible but the costs related with gene therapy make this impossible to achieve (Sade, 1998).

Personal Viewpoint on Gene Therapy

Personally, I think gene therapy as a technique for treatment of gene disorders and diseases is better than use of numerous medications that may have to be used for a lifetime. However, there are some aspects of gene therapy that I do not agree with especially the germline gene therapy technique. I believe that a human being’s body is very precious and only an individual should have the power to decide what should be done or not done to their bodies.

However, with gene therapy, this is not the case because the parents decide for their children and their entire generation on how their bodies will be and function. I believe that those children have the right to make their own decisions on the issue. It would be very sad if the genes added into the children’s’ body cells have negative effects on their growth and lives (Anderson, 1989).  No parent would live with themselves knowing they made a decision that ruined their children’s lives. I believe the somatic gene therapy is a better choice since it does not target the reproductive cells. In this case, even if the children are later born with a certain disorder, they can have the freedom to decide how they want it fixed.

Looking at the costs associated with gene therapy, I feel that it does not do much for the low-income people. This technique is obviously expensive and considering the many procedures involved, it is bound to get even more costly by the time all the research is completed. I believe gene therapy has the answer to some of the deadliest diseases such as cancer which nowadays affect even young children. However, with the costs involved, treatment for such diseases may remain to be just a dream for many in the society. The government could do more in helping make these technique accessible to more people if it is to really make a difference and change lives.

There are tremendous advancements in medicine that have come up over the years. It is important for people to take time to understand what all techniques or types of treatments involve before making decisions on what type of treatment to take. For me, treatment options are not about just costs, it is also about the future consequences it may have and about my conscious. I would not want to do something that I would regret for the rest of my life. Gene therapy has the power to transform lives either positively or negatively. Thorough knowledge of all issues involved could help patients make the right decisions. Although most of gene therapy techniques are still in the experimental stage, they are bound to bring major transformations in the medical field.

References

Anderson, W. F. (1989). Human gene therapy: why draw a line? Journal of Medicine and Philosophy, 681-693.

Sade, R. M. (1998). Gene therapy: Ethical and social issues. Journal-South Carolina Medical Association, 406-410.

Wirth, T. P.-H. (2013). History of gene therapy. Gene 525, 162-169.

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Leptin-Anathomy and physiology

Human Reproduction PowerPoint Presentation

Question

Well, it is that time—yes, time for that talk. For this activity, you will develop a PowerPoint Presentation about human reproduction. You are to pretend that the presentation is what you will use to give your son or daughter “the talk” about human reproduction. Make sure you use correct terminology. If you have never created a PowerPoint Presentation, make sure you view the CSU Success Center videos suggested in the unit learning activity.

Your presentation must include the following:

? overall purpose of the reproductive systems;

? information about the male and female systems including:

o at least two visual aids illustrating the two systems, and

o structure and function of the major organs of both male and females systems;

? methods of practicing “safe sex” and preventing pregnancy; and

? STDs.

Sample paper

Human Reproduction PowerPoint Presentation

Speaker notes

The primary role of the reproductive system is to ensure perpetuation of the species. In humans, the reproductive system plays a crucial role in reproduction. The male reproductive system produces sperms through a process known as spermatogenesis. The male reproductive system also delivers the sperms to the female reproductive system where they meet and fertilize an egg released from the ovary. Apart from procreation, the reproductive system produces hormones that help in achieving sexual maturity and development of secondary sexual characteristics in both males and females. Some of the hormones produced by the reproductive system include testosterone hormone and estrogen hormone. The reproductive system stores gametes, which are specialized sex cells containing a single set of unpaired chromosomes.

The male reproductive system plays two crucial roles: sperm production and introducing the sperms to the female reproductive system (Sherwood, 2012). Testes are the organs involved in sperm production. The testes are enclosed in the scrotum that hangs outside the body for optimal temperatures required in sperm production (35 degrees Celsius).  The testes are made up of coiled tube where sperm production occurs. Several glands produce semen, which acts as the transport vehicle as well as providing nutrients for sperms. These glands include prostate gland, seminal vesicles, and bulbourethral glands. The penis deposits semen into the female reproductive system during copulation. The glans of the penis becomes stimulated during sex, which leads to ejaculation. Sperm travels through various tubes such as epididymis, vas deferens, and the ejaculatory duct (Sherwood, 2012). It finally reaches the urethra that runs along the length of the penis.

The female reproductive system is mostly internal. The female reproductive system has six essential functions. These include ova production, sperm reception and conception, maintaining pregnancy, giving birth, and nourishing the young one (Sherwood, 2012). The ovaries are the organs that release an ovum. The fallopian tubes lie close to the ovaries. Once the ovum is released, it travels through the fallopian tube to the fertilization site. If the egg meets the sperm while in the fallopian tube, fertilization occurs. The fertilized ovum continues travelling until it reaches the uterus. The uterus is a hollow body where a fertilized egg attaches itself to the walls and continues to develop for a period of 9 months. The uterus maintains the fertilized egg until birth. The uterus is responsible for expelling the fetus after 9 months. At the lower part of the uterus is the cervix. The cervix is a narrow opening that permits the sperms to move up to the fallopian tubes for fertilization to occur. The cervix acts as the passageway for the baby during birth.

The testes are an oval-like structure that is suspended outside the body. The testes are the organs where sperms are produced. The testes also produce the testosterone hormone. The epididymis is a long curved tube located at the margin of the testes. It transports sperms from the testes. Within the testes, there are seminal vesicles, prostate gland, and bulbourethral gland. The seminal vesicle contains the liquid that forms semen when mixed with sperms. The prostate gland secretes the prostate fluid, which also forms part of semen. The prostate gland is also important during the ejaculation process. The bulbourethral gland also secretes fluid that adds to semen. Another major organ is the vas deferens. This is a long narrow tube joins the epididymis to the urethra. The vas deferens introduces sperms into the urethra during ejaculation. The penis becomes hard while erect and introduces the sperms into the vagina (Sherwood, 2012).

The vagina is one of the major organs in the female reproductive system. The vagina receives sperms during copulation. The vagina is also known as birth canal since it serves as the exit point when the baby leaves the womb during birth (Sherwood, 2012). The cervix is a narrow opening at the bottom of the uterus. The cervix allows menstrual blood to flow out of the uterus and into the vagina. The cervix also directs the sperms towards the uterus after intercourse. The uterus is hollow and contains thick walls. The uterus maintains the fetus from the early stages to birth. During birth, the uterus contracts thus expelling the fetus. The fallopian tubes are narrow tubes where the ovum travels through to meet the sperm. Fertilization occurs in the fallopian tubes. The last major organ is the ovary. The ovary is located along the lateral walls of the uterus. The ovaries serve as the sites where oocytes or eggs develop (Sherwood, 2012).

“Safe sex” refers to sexual intercourse that does not involve exchanging semen or vaginal fluids between couples. Individuals are advised to use condoms, which significantly reduce the risk of infections and unwanted pregnancy. Condoms should be used correctly as well as consistently. This improves their effectiveness. Inconsistent and incorrect use of condoms may lead to transmission of STIs. Among married couples, they can practice “safe sex” by being faithful to one partner and undergoing regular STI screening.

There are various methods available for preventing pregnancy. Common methods include natural methods (abstinence and rhythm method), use of condoms, diaphragm & spermicidal jelly, use of contraceptive pills, intrauterine device (IUD), and implants (Russell, Herz, & McMillan, 2015). Abstinence refers to restraining oneself from sexual intercourse. The rhythm method involves analyzing a woman’s fertility cycle, and thus having sex when a woman is unlikely to conceive. There are male and female condoms that act as a physical barrier preventing sexually transmitted infections and the risk of pregnancy. Diaphragm refers to a cup-shaped barrier inserted in the cervix. This prevents sperms from swimming up to the fallopian tubes. Spermicidal jelly is a chemical that is placed at the center of the diaphragm to kill sperms. Contraceptive pills are of different types. Majority of them contain the hormones estrogen and progestin (Russell, Herz, & McMillan, 2015). By changing the hormonal balance in the body, they are able to prevent pregnancy. The IUD is a metal device inserted into the uterus to prevent implantation. The implant contains hormones and is inserted under the skin.

STDs refers to diseases that are transmitted through sex. This may be oral sex, vaginal sex, or anal sex (Holmes, 2008). STDs are normally transmitted during unprotected sex from an infected person to a healthy person. STDs include viral diseases such as HIV & AIDS. Common STDs include gonorrhea, herpes, human papillomavirus (HPV), syphilis, scabies (may be transmitted through skin contact and through sex), pubic lice, pelvic inflammatory disease (PID), and among others. Some STDs do not produce obvious signs or symptoms, meaning that individuals may unknowingly pass them to others. Such STDs include syphilis, HPV, and HIV & AIDS.

Leptin-Anathomy and physiology

Leptin-Anathomy and physiology

Leptin

The discovery of leptin hormone in 1994 heralded a new dawn in the medical world, and specifically in the understanding of obesity. Leptin hormone plays a critical role in that it regulates energy balance in the body, thus affecting obesity. Over the last two decades, scientists have made significant discoveries on the various roles that the hormone plays in the body. This paper provides an in-depth review of the leptin hormone and the roles that it plays in the body.

Leptin belongs in the category of adipocyte hormones. Leptin secretion occurs in response to lipid storage in the body (Takanashi et al., 2017). The major role of leptin is in regulating energy metabolism in the body. It achieves this role through three mechanisms, which primarily involve acting in the brain. First, leptin inhibits food intake. Second, leptin stimulates the breakdown of lipids in the adipose tissue, a process known as lipolysis. Third, leptin enhances peripheral insulin sensitivity, which is how peripheral tissues such as muscle and others can absorb fat (Takanashi et al., 2017). These three effects are very critical in the human body and in development of medicines. It is because of the three mechanisms that leptin is currently applied in managing various pathogenic conditions, including diabetes and obesity. Leptin is effective in improving glucose metabolism in the body. It is vital in managing the complications that arise from diabetes and obesity.

Leptin hormone acts through the brain or central nervous system (CNS). Leptin has significant impacts on synaptic plasticity (strengthening and weakening of synapses) in the arcuate nucleus of the hypothalamus (Elmquist & Flier, 2004). Leptin hormone targets the articulate nucleus of the hypothalamus. The arcuate nucleus comprises of a group of neurons in the hypothalamus that help in mediating different physiological and neuroendocrine functions. The articular nucleus has two different groups of neurons. These groups of neurons have a different influence on food intake. The first group of neurons induces appetite through production of neuropeptides NPY and agouti-related protein (AgRP) (Elmquist & Flier, 2004). The neuropeptide and the agouti protein stimulate appetite. The second group comprises of appetite-inhibiting neurons. These neurons produce neuropeptides POMC and a protein known as cocaine-and amphetamine-regulated transcript (CART). Both groups of neurons have leptin receptors, but they act in opposite ways.

Leptin has a direct action on the POMC/CART activation, which in turn blocks the NPY/AgRP neurons. In addition, NPY/AgRP produces a neurotransmitter known as GABA that acts as an inhibitor (Takanashi et al., 2017). This neurotransmitter sends messages to POMC/CART resulting to their inhibition. In situations where an individual suffers from inadequate levels of leptin, the inhibitory actions to the POMC/CART and NPY/AgRP are compromised (Elmquist & Flier, 2004). This inhibits the appetite suppression process, leading to increased food intake levels in the individual. Inadequate levels of leptin thus leads to high excitatory effect on the NPY/AgRP neurons and less excitatory effect on the POMC/CART neurons. Studies indicate that repletion of leptin hormone in mice reverses these effects (Šabovič & Mavri, 2016). This is a clear indication that leptin hormone has a great potential in the management of diabetes and obesity in humans.

The following diagram shows leptin’s interaction with the brain leading to energy balance in the body.

Fig. 1.1.

It is possible to see that leptin has a direct action on the arcuate nucleus neurons by binding on the receptors. Leptin affects the neurons in different ways, thus controlling appetite. Presence of leptin activates the POMC, while inhibiting the NPY.

References

Elmquist, J. K., & Flier, J. S. (2004). Neuroscience. The fat-brain axis enters a new dimension.    Science (New York, N.Y.), 304(5667), 63-64. doi:10.1126/science.1096746

Šabovič, M., & Mavri, A. (2016). leptin and obesity – neuroendocrine , metabolic and      atherogenic effects of leptin. Zdravniški Vestnik, 72(1)

Takanashi, M., Taira, Y., Okazaki, S., Takase, S., Kimura, T., Li, C. C., . . . Okazaki, H. (2017). Role of hormone-sensitive lipase in leptin-promoted fat loss and glucose     lowering. Journal of Atherosclerosis and Thrombosis, doi:10.5551/jat.39552

Balancing Ecosystems

ACHIEVEMENTS IN BIOLOGY

Question

Discoveries in DNA, cell biology, evolution, biotechnology have been among the major achievements in biology over the past 200 years with accelerated discoveries and insights over the last 50 years. Consider the progress we have made in these areas of human knowledge. Present at least three of the discoveries you find to be most important and describe their significance to society, health, and the culture of modern life.

Answer

ACHIEVEMENTS IN BIOLOGY

Introduction

In lifetime, human beings performed major scientific processes for example using microorganism in production of drinks and foods without discerning the microbial processes behind it. But due to more research discoveries of regulatory mechanisms and biosynthetic pathways that microorganism utilizes to produce several metabolites has brought much insight. Such developments have influenced technologies of fermentation, monoclonal antibody, and enzymes. Beneficial microbes take part in fermentation mechanism, giving rise to plentiful helpful metabolites such as flavors, nutritious foods, amino acids, solvents and growth regulators (Soccol, 2013). Bioprocessing technologies have been beneficial for food processing industries i.e. dairy, beverage and alcohol processing. The example only gives a nip of significant advancements in biology for the past 200 years, and more is to be discussed in this paper into details, illustrating how useful they are to the society.

Genetically modified organisms (GMOs)

A genetically modified organism is an outcome of a laboratory procedure where genes from the DNA of a separate species are obtained and artificially forced into the genes of an unrelated plant or animal (Ahmed, 2011). The genes may be extracted from bacteria, insects, viruses, humans or animals. They are always referred to as transgenic organisms due to the genes transfer process (Ahmed, 2011). It becomes one of the exemplary evolution in genetic engineering which is deemed to be heading to a much better scales like cheap production of oral vaccines naturally from a fruit. Such a vaccine illustrates the spread in usage of this scientific tool for medical purposes and paves the way for the use of technology in modifying human genomes.

The conception of this technology has also lead to the invention of genetically modified foods. These are food products that are deduced in part or whole from the genetically modified organisms like microbes like yeast, animals or crop plants (Ahmed, 2011). The primary ingredients used in genetically modified foods are currently obtained from genetically modified soybeans, canola, and maize. The eminent success of this technology is the transformation of Tobacco Mosaics Virus to infect host plant and thereby producing immunizing protein in place of debilitating leaf shrivel. The process has in turn changed the greenhouse tobacco into a bio-factory for plague vaccine. Scientist perceives that this process may in the future lead to fish that can mature faster, nut trees, and fruit with earlier maturity and bananas that produce human vaccines. Statistics indicates that by 2003 167 million acres were already cultivated with GMOs (Hillstrom, 2012).

Treatment of genetic disease may be achievable through genetic engineering in case a profound study is performed. For instance, if the defective genes in an organism that causes disorder could be discovered and sited in a group of cells it could get substituted with a functioning one. The transgenic cells can thereafter be planted to actualize the disorder treatment. Cloning is another comparatively newer sector of biotechnology, but it could be the solution to imperative surgery problems. In case of a breakthrough organs and tissues could be cloned for use in surgical purpose.

Pharmacy

Pharmacy is a sector of health that has mostly benefitted from the discoveries surrounding the DNA, since biotechnology production of effective and cheaper drugs have been attained. Recombinant DNA is utilized for specific enzyme manufacturing enhances the production of diverse antibodies in an organism (Emery, 2011). It helps in the manufacture of hormones such as human growth hormone, insulin, and somatostatin readily and cheaply. Somatostatin, a brain hormone originating from the hypothalamus is the first ever human hormone that was synthesized through genetic engineering (Emery, 2011). It plays part to inhibit the discharge of insulin and human growth hormone that plays a part in the treatment of pancreatitis diabetes and other health conditions.

Recombinant DNA technology has seen an increase in manufacture of antibiotics which are chemical substances produced by microorganisms. For example, the rate of penicillin production has improved from 10 unit/ml in 1950 to 150,000 unit/ml at present (Emery, 2011). Numerous companies have utilized genetic engineering in the production of hormones such as Genentech a company based in California has manufactured human growth hormone from the genetically engineered bacteria. Another company Eli Lily in 1982 produced human insulin the first ever genetically engineered pharmaceutical.  Bovine Somatotropin hormone is also important when administered on cows because it realizes a large quantity of milk production.

Recombinant DNA technology has been used to produce interferon that is prepared in yeast by a fermentation process, it is an anti-viral protein produced from the mammalian cells. By cloning complementary DNA for human interferon, a difference in the amino acids properties and sequence has been noticed in a significant number of interferon. According to a scientist by name, Shroff he predicts that more convenient vaccines in friendly forms will be produced in future like inform of mouthwash.

The capability to produce large quantities of drugs through genetic engineering has led to efficiency in the treatment of various diseases hence having a positive impact on human health. The results of the drugs produced through this technology have proven its effectiveness and have very few side effects. To advance further in the benefits of using this technology scientists are researching on how to get vaccines for sicknesses such as flu, AIDS, hepatitis and malaria which tend to be the cause of many deaths in the world today.

 

Genetic code

Breaking the genetic code is believed to be the greatest revolution by the scientist to develop tools that can aid in the investigation of the molecules of life with an utmost accuracy (Jones, 2011). These biological developments are being blended with the ever advancing field of computers to help determine the problems that might be lingering in the future. The new scientific discipline that involves both computer and biology has led to the development of Bioinformatics. It is a system that stores large genetic data i.e. RNA, DNA, protein sequence, and amino acids of various organisms from bacteria to human beings that are generated throughout the world and stored in the database (Jones, 2011). Specialized software programs have also been developed that are used to visualize, find and analyze about the organism and share the information with the people concerned.

With all these information in place, various computer tools can assist in predicting protein structure that is vital in the development of more effective drugs and vaccines. By using microarray chips that are miniature arrays attached to glass slides of gene fragments, bioinformatics helps in early detection of various diseases like diabetes, cancer, etc. (Jones, 2011). A Phylogenetic tree can also be constructed basing on the molecular biology by the utility of this technology, the tree can highly contribute to the study of evolution (Jones, 2011). The technology has a potential to preserve a complete DNA sequence or genomes of an endangered species. Besides that it can also be used to model simulations of population dynamics, work out the cumulative genetic status of a breeding pool as well.

Conclusion

Biology indeed forms a vital part of the human life, the scarce resource that are available are not sufficient for the human nature to depend on hence a dire need for scientific involvement. The advancements in biology have achieved greater steps, such as getting solutions to chronic illnesses that were claiming life earlier to a point when such can be contained. For instance, the recent Ebola virus medicine that was discovered in the United States has made disease curable that which would claim lives of many and make people live in fear. All these indicate a promising future for biology where major revolutionary technology may be invented as a solution to various issues that have not been addressed. Biotechnology, on the other hand, has been strengthened by the recent advances in synthetic biology, bioenergy, DNA computers, bioremediation, bio-nanotechnology, proteomics, bioinformatics, genomics and virtual cell. Therefore biotechnology will in future be very powerful and have a profound part to play in finding solutions to critical global issues like global epidemic, global warming, poverty, and rising petroleum fuel crisis.

Reference

Ahmed, F. (2011). Testing of genetically modified organisms in foods. New York: Food Products Press.

Emery, A. (2011). An introduction to recombinant DNA. Chichester [Sussex: Wiley.

Hillstrom, K. (2012). Genetically modified foods. Detroit: Lucent Books, Gale Cengage Learning.

Jones, P. (2011). The genetic code. New York, NY: Chelsea House.

Soccol, C. (2013). Fermentation processes engineering in the food industry. Boca Raton, Fla.: CRC ;.

Balancing Ecosystems

The Discovery of DNA

Question

1.Discuss how the unique physical and chemical properties of water contribute to the importance of water for life on Earth to survive.

2.Discuss how the methods of experimentation and observation have changed throughout the history of science.

3.Explain the role so called “accidental” discoveries played in the history of science.

4.Describe the major experiments and scientists involved in the discovery of DNA as our hereditary material and its structure.

5.Explain what role women played in the Scientific Revolution of the 18th Century? What role do women in science play today?This assignment will be worth 20% of your grade.  Your paper should be creative and interesting, and should be a minimum 1500 to 2000 words in length. It should be well-organized and demonstrate an orderly flow of information that clearly addresses the subject chosen.

Answer

The Discovery of DNA

The discovery of DNA as the hereditary material and its structure marked a major milestone in the understanding of genetics and transfer of hereditary information. In the mid twentieth century, scientists were able to get a clear understanding of the structure and chemical nature of DNA. Prior to this, various speculations existed on what kind of molecules carried hereditary information. Some scientists associated transfer of hereditary information to proteins, while others speculated that transfer of hereditary information was facilitated by unknown molecules which they had yet discovered. Eventually, DNA was identified as the molecule responsible for the transfer of hereditary information across generations.

DNA was first identified by Friedrich Miescher and subsequently named “nuclein” in 1869 (Betz, 2011). Nuclein was later called nucleic acid and finally deoxyribonucleic acid (DNA). Miescher was at the time studying white blood cells. The task involved isolating the different molecules that make up cells. He was able to isolate the DNA molecule as a discrete molecule alongside its associated proteins. The experiments further revealed that the nuclein molecule was composed of phosphorous, hydrogen, oxygen and nitrogen. In addition, the ratio of phosphorous to nitrogen was unique. Interestingly, Miescher associated proteins with the transfer of hereditary information due to the wide variety in which they were found. His belief was in accordance with those of other scientists of the time. Nonetheless, his research laid the foundation for more research in molecules and the DNA (Betz, 2011).

The link between DNA and hereditary information was only discovered much later, precisely in 1944 by a biologist known as Oswald Avery (Alcamo, 2001). Prior to this, other scientists had carried out extensive experiments on DNA research to establish what controlled heredity. Gregor Mendel’s experiments for instance indicated that inherited traits were controlled by what he termed as factors that were derived from parents. Mendel conducted extensive research with pea plants which revealed that parents passed on certain traits to their offspring. The experiments also revealed that certain factors became dominant over other factors. In early 1900, Mendel’s observations were verified after it was noted that the factors which determined inheritance were actually chromosomes (Alcamo, 2001). Other experiments by scientists such as Morgan in 1910 verified Mendel’s observations. Morgan noted that the white eye color in some fruit flies was the result of a single chromosome.

Oswald Avery conducted investigations on heredity using the bacteria responsible for pneumonia. These bacteria were classified into two types; the S type bacteria and the R type bacteria. The S type bacteria were enclosed by an outer layer known as capsule, while the R type bacteria did not have a capsule or the outer layer (Seising, 2009). Avery’s experiments indicated that the DNA was responsible for the changes in the outer structure of the pneumonia bacteria. Thus, DNA could alter the characteristics of the bacteria, changing the R type pneumonia bacteria into the S form. Other molecules proteins did not have the potential for bringing changes in the outer structure of the bacteria. This led to the conclusion that DNA contained the hereditary information that was passed from one generation to the next one. Oswald Avery’s experiments and findings were supported by other biologists such as Colin Macleod and Maclyn McCarty (Seising, 2009).

Oswald Avery’s experiments were confirmed almost a decade later by scientists Martha Chase and Alfred Hershey (Alcamo, 2001). The duo conducted separate experiments on heredity which indicated that proteins had no role to play in the transfer of hereditary information. They used bacteriophages in their experiments to determine the transfer of hereditary information. Bacteriophages are those viruses that can infect and replicate within bacteria. They are primarily composed of DNA and protein (Alcamo, 2001). The duo employed radioactive labels in their experiments. The radioactive labels were designed to precisely integrate with either the protein or DNA, but not integrate in both. The duo showed that the action of bacteriophages involves infecting the bacterial cell with their own DNA, ultimately leading to the development of multiple copies of the viruses. The experimental results thus indicated that the injected DNA had an active role to play in directing the production of new viruses in the bacterial cells. Although it was not clearly understood how replication of new viruses occurred, new research over time found that the new DNA guides the formation of only the viral DNA in bacterial cells.

Following the discovery of the role of the DNA in transfer of hereditary information across generations, scientists still had a vague understanding of the structure of a DNA molecule. In the 1950s, scientists were more inclined in deciphering the structure of DNA. The drive to understand the structure of DNA was as a result of two reasons: to start with, understanding the structure of the DNA meant that scientists could be able to clearly tell how the DNA functions during the hereditary process; secondly, understanding the structure of the molecule could enable scientists to know how DNA is duplicated in cellular reproduction (Alcamo, 2001). Cellular reproduction and transfer of genetic information are the fundamental processes which scientists seek to understand. Understanding of structure of the DNA was an important breakthrough in the 20th century. It enabled scientists to understand how heredity works in detail.

In 1953, James Watson and Francis Crick made yet another scientific breakthrough in understanding heredity, specifically in shedding light on the structure of the DNA. The duo discovered the double-helix structure of the DNA which significantly changed molecular biologists’ understanding of the DNA (Tobin & Dusheck, 2005). Prior to the discovery, scientists held the view that the DNA was triple stranded. This was the assumption found in many textbooks and the view held by many. These incorrect assumptions made it difficult for scientists to understand how DNA works. The discovery of the true DNA structure significantly helped in the development of various gene techniques such as rapid gene sequencing, understanding monoclonal antibodies, development in the field of genetic engineering and lastly helped develop the biotechnology industry.

Watson and Crick knew that understanding the structure of the DNA would shed light in the field of molecular biology. The duo conducted no experiments of their own, but dwelled on the experimental works of other molecular scientists in deciphering the structure of the DNA (Lewis, 2009). Watson and Crick employed the use of stick-and-ball models in order to arrive on possible structures of the DNA. Over a period of two years, the duo became immersed in various fields of science such as genetics, physical chemistry, chemistry, X-ray crystallography and biochemistry. Crick had extensive knowledge in X-ray crystallography and physics while Watson had a deep understanding of bacterial and viral genetics. This, combined with other factors such as persistence, brilliance and luck enabled them to correctly come up with the double helix structure of the DNA. The duo was able to show that DNA is not only simple but also complex enough to be the one responsible for passing of hereditary information across generations.

In early 1950s, numerous researches existed on the structure of the DNA; however, the findings were unconnected and offered little or no insight into the true structure of the DNA. Watson and Crick took it upon themselves to develop a comprehensive theory of heredity by analyzing the existing researches and drawing connections from the different findings. Alexander Todd, a renowned organic chemist at the time had already concluded that a DNA molecule comprised of repeating deoxyribose sugar groups and phosphate groups. Erwin Chargaff had discovered that the bases adenine, guanine, cytosine, and thymine, as well as the amount of DNA varied widely across species. He also noted that A & T, and G & C occurred in specific rations of one-to-one (Lewis, 2009). Other biologists such as Rosalind Franklin and Maurice Wilkins were also instrumental in understanding the structure of the DNA molecule. Franklin and Maurice employed the use of X-rays to understand the structure of the DNA.

Shining X-rays on biological molecules such as deoxyribonucleic acid can enable researchers observe complex patterns and hence determine the structure of the DNA. Although Franklin and Maurice obtained the diffraction photos from DNA, they were still unable to comprehensively draw on the structure of the DNA. In 1953 Watson and Crick, working on drawing connections between various scientific researches, stumbled upon Franklin and Maurice’s DNA X-ray diffraction photos which they had taken during their experiments (Tobin & Dusheck, 2005). The photo provided Watson and Crick with clues about the actual structure of a DNA molecule. The photo had what appeared as a fuzzy X at the center of the molecule, which pointed towards a helical structure of the DNA.

Drawing on experimental works from other scientists, Watson and Crick were able to learn the true structure of a DNA molecule. They also came to learn that most textbooks were wrong on the idea of how the elements carbon, hydrogen, nitrogen and oxygen are configured in guanine and thymine. In the earlier incorrect understanding, hydrogen atom was joined to an oxygen atom, while in the new and correct understanding, a hydrogen atom bonds with a nitrogen atom (Tobin & Dusheck, 2005). It is then that Watson realized that A always joined with T, and C with G. The pairs were held together by hydrogen bonds. In addition, Watson realized that the observation supported Chargaff’s conclusions on the ratios in which A & T, and G & C occurred. Watson and Crick thus discovered the double helix structure of the DNA.

References

Alcamo, I. E. (2001). DNA technology: The awesome skill. San Diego: Academic Press.

Betz, F. (2011). Managing science: Methodology and organization of research. New York:          Springer.

Lewis, R. (2009). Discovery: Science as a Window to the World. Chichester: John Wiley & Sons.

Seising, R. (2009). Views on fuzzy sets and systems from different perspectives: Philosophy and   logic, criticisms and applications. Berlin: Springer.

Tobin, A. J., & Dusheck, J. (2005). Asking about life. Belmont, Calif: Brooks/Cole

 

The Success of Insects

The Success of Insects

Question

Topic : The Earth’s largest phylum is Arthropoda, including centipedes, millipedes, crustaceans, and insects. The insects have shown to be a particularly successful class within the phylum. What biological characteristics have contributed to the success of insects? In many science fiction scenarios, post

Answer

The Success of Insects

Insects are some of the most successful organisms on the planet. There are a number of factors which have contributed to insects’ success on earth. Of the factors is because insects are adapted to live in different types of habitats. Insects are widely distributed on earth (Beerling, 2007). They are able to live across different ecosystems such as deserts, hot springs, tropical rain forests, arctic habitats and among others. Insects have a high reproductive capacity. Most insects are able to give a large number of offspring within a short period. This increases their numbers. Their relatively small size also contributes to their success. The small size means that they require less energy and also the less time in completing the developmental cycle. Insects have different appendages such as mouthparts, wings and legs. The mouthparts enable them feed on variety of food substances. Other appendages such as wings enable them disperse more and avoid predators. Lastly, insects have an exoskeleton which reduces water loss (Beerling, 2007).

Post-apocalyptic earth is depicted with giant insects. However today, there are no such giant insects. There a number of theories which explain the extinction of giant insects. One of the possible reasons is harsh environmental conditions which lead to their extinction. For instance a severe drought could largely affect giant insects since they need more energy leading to their extinction. The reproduction rate among giant insects could have been slow. This factor combined with other factors such as drought could have led to a mass extinction. Giant insects may also have been wiped off by super predators which preyed on them to an extent of mass extinction. Another possible version of super predators is when the predators (in this case giant insects) evolve and devours the prey more than it can naturally replace its numbers. The extinction of the prey subsequently leads to death of the super predators. Lastly, giant insects could have become extinct due to lack of adequate supply of oxygen. Larger insects are particularly vulnerable to oxygen concentrations (Beerling, 2007).

Reference

Beerling, D. J. (2007). The emerald planet: How plants changed Earth’s history. Oxford: Oxford             University Press.

Balancing Ecosystems

Organisms in the Domains Bacteria and Archaea

Question

Discuss the similarities and differences between organisms in the domains Bacteria and Archaea

Answer

Organisms in the Domains Bacteria and Archaea

Archaea were formerly classified as bacteria with the name archaebacteria due to a number of similarities between them and bacteria. It is only after careful studies that scientists discovered the distinct biochemistry and evolutionary history between them (Pommerville, 2014). There are a number of similarities between archaea and bacteria. To start with, archaea and bacteria have basically the same size, shape and appearance. Secondly, both of the organisms multiply through binary fission which is a form of asexual reproduction. Thirdly, the primary means by which both organisms move is through the use of flagella. Fourthly, both are classified as prokaryotes since they lack a complex cell structure common among eukaryotes. Lastly, they both contain semi-permeable cell membranes that allow selective movement of elements or substances through them (Pommerville, 2014).

There are a number of differences found between archaea and bacteria that sets them apart. One of the notable differences is that bacteria have cell walls which contain peptidoglycan, which is a polymer consisting of amino acids and sugars (Pommerville, 2014). Archaea cell walls are made up of pseudopeptidoglycan, which partly comprise of N-acetyltalosaminuronic acid. There exist differences in the type of lipid bonding that occurs in the membranes of bacteria and archaea. Archaea membrane lipids are held together by ether bonds while in bacteria ester bonds occur. Archaeal lipids do not have fatty acids which are common in bacteria. Instead, the lipids are made up of side chains which comprise of isoprene units. The RNA in archaea is more complex to the one found in bacteria. Bacteria contain simple RNA polymerases. They also contain metabolic differences. Bacteria use glycolysis to breakdown glucose while archaea use a different process. Lastly, majority of Archaea lack the Kreb’s Cycle pathways which is common in bacteria (Pommerville, 2014).

 

Reference

Pommerville, J. C. (2014). Fundamentals of microbiology. Burlington, MA: Jones & Bartlett       Learning.

Balancing Ecosystems

Genetic Drift

Genetic Drift

 

Genetic drift is the change or fluctuations that occur in gene variants in a particular population (Jacquez, 2015). Genetic drift occurs when variant genes known as alleles change in number, either decreasing or increasing over time by chance. Genetic drift occurs in two types: the bottle neck effect and the founder effect.

The bottle neck effect is observed when a large percentage of a particular population is decimated mostly through a natural disaster such as floods or fire. The natural disaster only leaves a few of the species to reproduce. The population left is not representative of the previous genetic makeup of the original population. A bottle neck effect can be seen when natural disasters decimate a large part of the population (Jacquez, 2015). For example, a fire outbreak in a forest may kill over 95 percent of beetles and leave the rest which begin to reproduce. The 5 percent of the beetles left could be having a different genetic makeup from the vast majority of the earlier population. The new population would thus be different from the original population in terms of genetic makeup.

The founder effect as a method of genetic drift occurs when a small part of a population move away and inhabit a new area. This can lead to development of a new population that is quite different from the source population. The founder effect presents itself in a particular population due to reduced genetic variation. The new population lacks much of genetic diversity that was present in the source population (Jacquez, 2015). A good example can be seen in human populations where prevalence of particular diseases such as Huntingnton’s disease occurs frequently in the area around Lake Maraciabo, Venezuela. The high prevalence of the disease is attributed to a small group of individuals who chose to remain in the area. Some of the people had Huntington’s disease, which became dominant as the population grew.

References

Jacquez, J. A. (2015). CliffsNotes STAAR EOC Algebra I quick review. Boston: Houghton Mifflin Harcourt.

 

Balancing Ecosystems