Writing in Biology

On pages 58-59, Thomson writes about how some opponents of abortion support the independence of the fetus, and how the fetus has a right to the mother’s body when it was conceived through voluntary intercourse. People often say the only case of involuntary pregnancy comes from rape. However, Thomson writes that it is a slippery slope to choose when a woman voluntarily or involuntarily becomes pregnant, as details can make a huge difference. First, Thomson describes a scenario where a woman opens her window because her room is stuffy, which allows a burglar to get in. Thomson then says how absurd it would be to say that the burglar has a right to stay in the room now that they have gotten in, even though the women technically allowed him to get in by opening her window. Although that may be absurd, a parallel could be drawn between this situation and woman becoming pregnant.

Melting point of the once recrystallized product was determined to be 53-55^oC. The melting point of the twice recrystallized product was determined to be 54^oC. In literature, the melting point of trimyristin was 57^oC. The narrowing melting point range after each recrystallization indicated a relatively pure product formed from recrystallization. The slightly lower melting point obtained versus in literature indicates some soluble impurities present. The product of the hydrolysis and acidification of trimyristin was determined to be myristic acid using melting point analysis. Melting point of the myristic acid was determined to be 51-52^oC and the literature value of expected melting point of myristic acid was 54^oC. The slightly lower melting point obtained as well as the narrow melting point range indicate subtle impurities.

In this lab trimyristin was isolated from the organic compound nutmeg in the presence of tert-methyl butyl ether. The crude trimyristin product was then recrystallized in the presence of acetone and hydrolyzed in the presence of sodium hydroxide and 95% ethanol and then acidified in the presence of hydrochloric acid. Recrystallized trimyristin was recrystallized a second time in the presence of acetone. The recrystallized product was determined to be trimyristin using melting point analysis with a yield of 23.7% after the first recrystallization and 6.0% after the second recrystallization based on the original amount of nutmeg used in the reaction.

         To a round-bottom flask was added nutmeg (1.00g) and tert-butyl methyl ether (3mL). Heating at boiling point was performed to the solution for 10 minutes. Micro-scale filtration was performed on the solution. Crude product was recrystallized from acetone (2mL) and cooled. To a round-bottom flask was added recrystallized trimyristin (60mg), 6M NaOH (2mL) and 95% ethanol (2mL). The solution was refluxed for 45 minutes. The solution was allowed to cool and poured in a beaker containing water (8mL). To the solution was added HCl (2mL) dropwise and stirred while cooled. Remaining recrystallized trimyristin was recrystallized from acetone (2mL). Melting point of product and both recrystallized trimyristin was determined.

In contrast, experiments have shown that a reduction in telomerase activity and the shorting of telomeres has been associated with aging. This highlights the importance of the maintenance of telomere length and protection in control of the cell cycle life span. Further research on the mechanism of telomere maintenance and shortening could provide important information regarding the development of cancer treatment, anti-aging strategies, and hereditary disease function. As the average life span of humans rapidly increases, research in this field will become even more important. 

More insight into the mechanism behind telomere maintenance and replication shed light on its role in cancer as well as aging. It was discovered that in 80-90% of cancers, an increase in telomerase activity can be shown. This indicates the role telomere shortening may play in preventing unwanted mutations and cancer. Once cells divide a certain number of times in healthy cells, unprotected and shortened telomeres trigger senescence and apoptosis. With overactive telomerase, this shortening is prevented and cells would be able to proliferate uncontrollable and an unlimited number of times.  This mechanism of induced senescence and apoptosis in cells with improper telomere function appears to be regulated by the tumor suppressor gene p53, which acts by binding damaged DNA and promotes p21 activity, a CDK inhibitor which induces cell arrest pathways. Since p53 function is inhibited in 70-80% of cancers, this provides a major hurdle for biologists moving forward in targeting drug therapies towards cancer cells with impaired telomeres.

The “end-replication problem” is one that puzzled many molecular biologists and biochemists for decades. Since a free 3’ OH group is needed for DNA replication and a new strand of DNA to be synthesized, this creates a problem for the ends of linear DNA molecules, such as those we see in eukaryotic cells. Investigation into this mystery began when Blackburn and Szostak sequenced the ends of linear DNA molecules from Tetrahymena and were able to ligate to the ends of yeast cells DNA. These experiments showed evolutionarily conserved properties of Tetrahymena rDNA end sequences with those similar sequences in yeast cells that led to functional telomeres. They were also able to identify repeated C_1-3A sequences in telomeres of both organisms. As a graduate student in Blackburn’s laboratory, Greider was able to identify G-rich rDNA molecules in Tetrahymena that contained the necessary 3-OH group for DNA replication that was complementary to the repeats seen in the telomere sequences. The addition of the G-rich oligonucleotide were also shown in vitro to enzymatically be added to yeast telomeric DNA. At this point, the scientists were able to establish a mechanism for telomere synthesis and maintenance involving the enzyme telomerase as a unique reverse transcriptase with an RNA template and protein components, the mystery had been solved.

In 2009 the Nobel Prize in Physiology or Medicine was awarded to three scientists for their discovery and research in telomeres and the enzyme telomerase. Since Watson and Crick published the structure of our DNA and Meselson and Stahl discovered the mechanism by which our DNA is replicated, a mechanism for how the ends of chromosomes can be replicated and maintained. Through years of work, Elizabeth Blackburn, Jack Szostak and Carol Greider were able to determine the mechanism for the replication of telomere DNA, its conserved nature evolutionarily, and key enzymes involved in the process such as telomerase. There findings could have great potential medical application in such fields as cancer and aging.

In 2009 the Nobel Prize in Physiology or Medicine was awarded to three scientists for their discovery and research in telomeres and the enzyme telomerase. Since Watson and Crick published the structure of our DNA and Meselson and Stahl discovered the mechanism by which our DNA is replicated, a mechanism for how the ends of chromosomes can be replicated and maintained. 

    In this experiment, 0.928 g of 3-methylbutyl propanoate were synthesized via a reaction between 0.973 mL of propanoic acid and 1.194 mL of 3-methyl-1-butanol. Sulfuric acid was used as a catalyst. The percent yield of the product is 58.51%. The 3-methylbutyl propanoate was purified and the identity confirmed by infrared spectroscopy (IR). The measured IR had a peak of 1751.361cmwhich confirms the ester although the value is slightly high. The IR also had peaks of 2980.02 1cm and 2873.94 1cmwhich indicate an alkyl CH stretch. 3-methylbutyl propanoate is an ester with a carbon chain and so these results are consistent with the product. The reactants, propanoic acid, 3-methyl-1-butanol, and sulfuric acid are all refluxed and the product of this distilled to ensure that the product is as pure as possible. There was also a peak of 3552.88 1cm which was an abnormal OH stretch and signifies that too much 3-methyl-1-butanol was added to the original mixture that did not evaporate during the reflux period, making the product impure. An electric pipet may have helped to eliminate measurement mistakes and prevent this abnormality.