Writing in Biology - Section 1

DefB103 shows that we have do not have 3 G’s in a row, (shown in Figure 3). Since the data gets messy after the 2 G’s, we are favorable for the deletion and can conclude that our dog does not have wild-type DefB103 gene. However, at the third G, there is a heterozygous peak (A/G): there is one copy of the DNA strand that has the 5 G’s in a row, while another copy of DNA does not have 5 G’s in a row. Having a copy of both 5 Gs and 2 Gs means that we can conclude that we are heterozygous for β-Defensin, so our dog’s genotype is K^B/k^Y at the K locus.

Schmutz and Dreger (n.d.) provide a table that answers the “phenotypes produced by the genotype interactions of ASIP, DEFB103, and MC1R in dogs.” Understanding that our dog has no e allele for MC1R, no a^y allele for ASIP, and is heterozygous for DEFB103, we can look at the table to predict our dog’s phenotype. Figure 6 shows the table that presents our dog’s genotype.

From this table, we can conclude that our dog’s phenotype has a black coat with black lips and a black mouth.

A new study done by researchers at Colombia University has identified serotonin as the chemical that triggers the body's startle response in fruit flies. This study shows that when a fruit fly is starlted with unexpected changes to its surroundings, levels of serotonin rise and this helps to stop the fly in its tracks. Since serotonin also exists in people, the results in this study may be a clue as to what happens inside our body with the serotinin levels when we become startled. Serotonin is closely associated with mood and emotion, but more recently, it has been shown to affect the speed of animals movement. The researchers found that serotonin levels in walking fruit flies varied when experiencing additional factors, such as different temperatures, walking upside down, and walking while hungry. Researchers found the biggest significant changes in serotonin levels when a sudden change to the fruit fly's environment occured, or when they were startled.

Plants have many ways of reproducing. Many plants sexually reproduce by pollination of eggs with pollen to create a diploid zygote from two gametes, much like how mammals reproduce. Some plants go into haploid spore forms that can live in a life cycle on their own by mitosis that then fuse together to form a diploid that creates spores again. And some plants, even with diploid genomics, reproduce by cloning. Such plants include strawberries, quaking aspen trees, poison ivy, and spider plants. Clonal growth has many advantages over other ways of reproducing. Firstly, cloning themselves allows for daughter plants to become fully formed by remaining connected to the parent plant, sharing nutrients, water, sugars, and other vital molecules until the daughter plants can be completely independent. Secondly, with quaking aspens as an example, there are plants that do not severe the connection between the parents and daughter plants, and instead maintain connections that allow the plants to share nutrients, signal molecules, and everything in them for as long as they live. This allowed quaking aspens to be the largest single organism in the world, covering hundreds of acres and living as long as four thousand years- having thought to started growing after the most recent ice age. 

Given that kuru was historically and geographically constrained and that there have been no cases of the disease since 2005, it is unsurprising that recent and future research into the disease has been limited. The most recent findings relating to kuru were reported by Mead et al. in their paper on genetic immunity to kuru in the Fore people (2009). Now that the disease is extinct, interest in the disease has faltered, only exacerbated by the fact that there are virtually no more intact kuru infected brains available for study (Hainfellner et al., 1997). Thus, although kuru has provided great insight into prion mediated neurodegeneration and was fundamental to the development of prion theory, it is no longer the object of much scientific research.

In summary, kuru is a neurodegenerative disorder that is historically constrained to the mid-20th century and geographically limited to the Fore speaking tribes of Papua New Guinea. It originated by spontaneous CJD in one individual and spread to other individuals via these tribes’ cannibalistic mortuary rites. Its root biological cause is prions, that produce neurotoxic compounds as they aggregate into undegradable deposits found most prominently the cerebral cortex, the cingulate cortex, the striatum, the thalamus, and the cerebellar cortex. Thus far, kuru can only be prevented by genetic immunity via mutations in the PrP gene. Otherwise, there is no cure for kuru and death is its only prognosis. 

In genetics, the central dogma pertains to DNA and its lifecycle within an organism.  DNA is the genetic material within the cell and codes for an amino acid sequence which is used to create protiens.  DNA also can produce regulatory agents within the cell.  DNA starts by being transcribed into RNA.  Depending whether or not the organism is a prokaryote or eukaryote, the process will vary.  In eukaryotes, there is more proteins, origins or replication and processing which goes into transcription becasue there is more DNA which is linear.  After the DNA is trascribed into RNA, the RNA is translated into an amino acid sequence.  The code of amino acids correlates to the codon (order of 2 nucleotides) which is matched up by the tRNA that brings in the amino acid to the chain.  From there, a proteins is produced from DNA.

Taphonomy is the study of factors affecting the decomposition of anything after its death.  This is an assemblage of both biotic and abiotic factors which affect the rate of decomposition which was accumulated both in the lifetime of the thing as well as after its death.  For example, a high quanity of mercury in the diet of an individual could have an effect on the taphonmy of the individual after its death.  Some biotic factors include insects, animal activity and human interferance.  Abiotic factors include the weather, soil acidity and exposure to sun.  

The principal and AL eyes may also work together to gather visual information. A recent study (Jakob et al., 2018) investigated how lateral eyes direct the principal eyes of jumping spiders when tracking objects. In order to test this,Phidippus audax spiders were tethered in front of an eyetracker that recorded the gaze direction of the principal eyes. Visual stimuli of different shapes and movement speeds were presented before and after masking the ALEs with removable paint. When unmasked spiders were shown a moving disk, the principal eye retinas moved close together and were able to track it. Meanwhile, spiders with their AL eyes masked were unable to track moving objects, with their principal eye retinas remaining further apart and reacting only briefly when the objects crossed their field of view. However, when the spiders were presented with a motionless object that appeared in the center of the principal eye’s field of view, they actively scanned it regardless of whether the secondary eyes were masked or unmasked. This indicates that masking the secondary eyes does not prevent the principal eyes from investigating stationary objects, but they are needed for targeting stimuli outside of the principal eye’s field of view (Jakob et al., 2018). The integration between principal and secondary eyes has also been studied in Cupiennius salei (Family Ctenidae). The principal eyes of ctenids are moveable, but they are controlled by four muscles instead of six as in jumping spiders (Kaps, 1996) (Land, 1969). Thus, they are not able to engage in complex movements such as torsion. When spiders had their principal eyes masked, they maintained the same eye muscle activity, but masking the secondary eyes reduced principal eye movement (Neuhofer et al., 2009). The researchers concluded that the secondary eyes of C. salei are involved in movement detection, while the principal eyes require input from the secondary eyes to move normally.

To facilitate handling, I placed the spider in a vial to rest in the freezer for 5-8 minutes, with frequent checks to make sure the spider was alive. I then removed the spider from the freezer and gently took it out of the vial using a brush. Next, I placed the spider on the center of a stretched-out piece of Parafilm. To enclose the spider, I folded the Parafilm over it and applied pressure around the spider. Then I carefully punctured the resulting air bubble with a pin, making sure that the spider remained unharmed. 

I placed the tightly wrapped spider over a sectioned quarter of a Styrofoam ball, so that it was centered on the curved surface. In order to secure it to the Styrofoam ball, I applied pressure over the extra Parafilm. With a pin, I then carefully removed the Parafilm over the spider’s head to reveal all its eyes, without exposing the spider’s chelicerae (Figure 5).

The following species were used in the trials (Figure 3): Xysticussp. and Mecaphesa celer (Thomisidae),Cheiracanthium inclusum(Eutichuridae, Ramírez, 2014), and Phidippus princeps. Phidippus princepsis an active diurnal hunter from the Salticidae family with high visual acuity, and was tested to confirm if the experimental set up provided the same results as those obtained by Jakob et al.(2018) using an eyetracker. Cheiracanthium inclusumis an active nocturnal hunter and has eight eyes evenly arranged in two rows of four. Xysticus sp.and M. celerare members of the family Thomisidae, characterized for being diurnal ambush predators that hunt pollinators in flowers. The principal eyes of Misumena vatia, another Thomisidae with a similar eye arrangement, overlap entirely with one pair of secondary eyes (the ALEs), and partially with the rest of secondary eyes (Insausti et al. 2011). The principal eye retinas of M. vatia are equipped with two muscles arranged similarly to those of C. salei(Insausti et al. 2011). The principal eyes of M. vatia have a wider field of view (Insausti et al. 2011) than those of jumping spiders. In thomisids, the PMEs look upwards for aiding in the detection of aerial prey like bees.  

A recent review (Morehouse et al., 2017) compiling the current knowledge on the evolution and molecular foundations of spider vision remarked on the need for further research in this area of investigation. While there is great variation regarding eye arrangements and visual systems across families, most studies on visual behavior have focused on spiders that have similar foraging strategies and do not represent the full range of spider visual morphology or behavior.

The visual systems of different spider families can be correlated to their life histories and behaviors. Many diurnal cursorial spiders like salticids possess enlarged principal eyes and use their secondary eyes to give them wide peripheral vision for detecting prey. Nocturnal hunters like wolf spiders (Family Lycosidae) and net-casting spiders (Family Deinopidae) have small principal eyes and enlarged secondary eyes. Meanwhile, some ambush predators like crab spiders (Family Thomisidae) and web-building spiders like long-jawed orb weavers (Family Tetragnathidae) tend to have small, evenly spaced eyes with little size difference between the principal and secondary eyes.