Writing in Biology

Fragile X Syndrome is a dominant X- linked syndrome, meaning it affects both men and women. Since men only have one x chrolmosome, it effects them more frequently and with more severity. With inheritance, the father passes on Fragile X only to the daughters since any sons will recieve a Y chromosome from him. If the mother has Fragile X or acts as a carrier for it, there is a 50% chance her children will be affected by it.

The Fragile X mutation was discovered in 1943 by two scientists, Bell and Martin. The disease was originally named after them, but then renamed after it was found to a sex-linked condition with a "fragile" site on the X chromorosome. The mutation that causes fragile X is a CGG repeat on the X that repeats more than normal. Normally, it repeats between 6 and 55 times. Anything over 55 repeats is considered fragile x.

About 50% f women with fragile x do not show any symptoms (long face, large ears, and flat feet). Also men and women who have between 55 and 200 CGG repeats have what is called "pre-mutation" fragile x. Pre mutation is incomplete fragile x but can cause multiple issues like ovarian failure and tremor ataxia syndrome. If someone has 200 or more CGG repeats, they have complete fragile x. The greater the number of repeats, the greater the severity of the effects. Those with fragile all show a silenced FMR1 gene with no FMRP proteins. 

Sharks and some other marine organisms are able to use electric signals to their advantage. Some organisms can emit electrical signals while others are highly sensitive to electrical signals. Sharks specifically are highly sensitive to electrical signals that can be used for communication and detection of the environment. Organisms that emit electrical signals can use their abilities for defense or killing prey as well. There are two main types of electrical receptors. The first being tuberous receptors which are found only in electric fish and respond to the high frequency discharge rates. The other type of electrical receptors is ampullary receptors. These receptors are found in both electric and non-electric fish and respond to much lower frequencies.

Using the Primer3 software, primers were created to amplify the region of the NaN1793 mutation. These primers were chosen with respect to the fact that Sanger sequencing can only sequence about 1000 b.p. maximum, and the mutation should not be too close to either primer since the beginning and end of sequencing data is usually less accurate than the middle. The expected size of the amplicon is 874 b.p. In order to confirm that DNA was extracted from the plants and to decide which samples to take for sequencing, gel electrophoresis was run. Two gels were run. One gel contains PCR products in a ¼ dilution in T10E1 (TE) buffer while the other contains PCR products in a ¼ dilution with H2O as a control. The T10E1 diluted DNA was preferentially taken for sequencing because it protects DNA from degradation, so that DNA should be of better quality than the H2O diluted DNA. Because there was no band in the Mutant 1 lane of the TE gel, Mutant 1 was taken from the H2O gel. Mutant 2, Mutant 6, and Mutant 7 were all taken from the TE gel. The DNA was extracted and purified from the gel and was nanodropped to confirm presence of DNA and assess purity. In order to perform Sanger sequencing, a primer is needed. The forward primer is 428 b.p. from the mutation site, while the reverse primer is 447 b.p. from the mutation site. The forward primer was used for sequencing because it is closer to the mutation site.

Organisms use vibration and sound perception sensory systems to help them respond to their environment. Snakes posses two sensory systems to respond to both airborne and substrate vibrations. Squid and Cuttlefish have a line of ciliated cells on their heads and tentacles that area analogues of lateral lines in fish. Water striders use water disturbance for sex determination. Males and females have different wave signals that they create. Pit vipers have pit organ neurons that overlap in their brain with visual neurons. This produces an infrared vision that allows them to detect prey.

Organisms have different specialized sensory systems. Many organisms are highly sensitive to small amounts of chemical substances. Many fish are highly sensitive to amino acids found in many marine mammals. Many fish are highly sensitive to amino acids. Taste buds are another sensory system that organisms have. Catfish have taste buds throughout their body and are essentially open pores with microvilli for increased surface area. Insects are hypothesized to have five different sensory neurons, each with a different purpose.

Organisms respond to an array of different environmental stimuli. Most responses to stimuli occur through the presence of accessory structures such as ears, nose, and eyes. Within each of these larger sensory structures are sensory neurons. Information is detected though these structures in three different ways. The first way is the sense organ can be directional as it gives different signals if turned toward or away from the source of the stimulus. The second way is when signals are obtained from a pair of similar sense organs and are compared. An example of this is hearing via two different ears. The third way is signals can be compared together in time and space.

There are two strategies to treating cancer through immunotherapy: passive and active. Passive immunotherapy involves treatments with monoclonal antibodies, adoptive T cell transfers, and genetically engineered T cells, whereas active immunotherapy involves vaccine-mediated immunity via the administration of tumor-associated antigens (Banerjee et al. 2018). Due to genetic alterations or post-translational modification of proteins, cancer cells can express and display proteins that differ from their normal cell counterparts or are overexpressed in the tumor phenotype (Battaglia et al. 2016). These proteins are known as tumor-associated antigens (TAA) and fail to be recognized by the immune system. As a result, cancer cells that display TAAs are able to evade the normal destructive response of active CD8+ T cells. Cancer vaccines serve as methods of active immunotherapy that can stimulate the CD8+ T cell response to these TAAs and hopefully eradicate all cancerous cells that display them (Banerjee et al. 2018).

The amount of a protein that is synthesized depends on the amount of the corresponding mRNA that is available for translation. The amount of available mRNA, in turn, depends on both the rate of mRNA synthesis and the rate of mRNA degradation. Eukaryotic mRNAs are generally more stable than bacterial mRNAs, which typically last only a few minutes before being degraded. Nonetheless, there is great variation in the stability of eukaryotic mRNAs: some persist for only a few minutes, whereas others last for hours, days, or even months. These variations can produce large differences in the amount of protein that is synthesized. Cellular RNA is degraded by ribonucleases, enzymes that specifically break down RNA. Most eukaryotic cells contain 10 or more types of ribonucleases, and there are several different pathways of mRNA degradation. In one pathway, the 5′ cap is first removed, followed by 5′→3′ removal of nucleotides. A second pathway begins at the 3′ end of the mRNA and removes nucleotides in the 3′→5′ direction. In a third pathway, the mRNA is cleaved at internal sites.

Genome editing (or gene editing) is a type of genetic engineering that involves modifying a living organism’s genome. Specific regions of the genome are deliberately targeted and DNA sequences are inserted, deleted, or otherwise modified to change the sequence at that location and alter gene function, either by preventing or enabling expression, or by changing how the gene is expressed (“Genome editing in brief: what, why and how?”, n.d.). Genetic disorders can affect both somatic (body) cells and germline cells (cells involved in reproduction, such as sperm and eggs). While genetic mutations in the DNA of somatic cells only affect the individual and cannot be inherited, changes in the germline DNA are heritable and can affect future offspring (Ormond et al. 2017). Genetic disorders can only be “cured” by targeting them at the genomic level, which these new advances in molecular and genetic technology have made possible. There are, however, concerns about its viability, ethics, and long- and short-term consequences, especially surrounding the topic of germline editing. Both somatic and germline cells can be edited, and while any changes made to the DNA of an individual's somatic cells will only affect that individual, changes made to their germline DNA could be inherited by their future children. The technology at present cannot guarantee that “unintended modifications created through an editing procedure would not result in a devastating long-term outcome such as cancer or adverse developmental effects if one were to modify a zygote” (Kohn, Porteus & Scharenberg, 2016), which has lead to mixed scientific and public opinions about its use.