Writing in Biology - Section 1

When an embryo is 2 weeks old, the heart muscles know their fate and they rearrange themselves in a crescent shape. Cells go to specific places and act as progenitors to form different parts like the atria, ventricles. By the third week, a tube forms that starts beating that later becomes the right ventricle. Other cells become the left ventricle. As time goes by the cells become more specific in terms of location. Newborns usually present problem only in a localized area, example, they could be born with all the chambers completely intact, but missing the right ventricle. They must have had a mutation in the cells responsible for the right ventricle that caused such a phenotype. Animal models such as chick, mouse, zebrafish embryos etc have been used to understand this process on a molecular level. However, animal models were difficult to study for very early stages. Thus, induced pluripotent stem cells became handy in order to study such preliminary phases. These cells mimic the cardiomyocytes in vivo. Together with stem cells in a dish and animal models, it was possible to understand the gene networks that chalk out the map for cardiac fate. His team was able to figure out the key components in the gene network: the Notch1, Gata4, Tbx5, Nkx2.5 and Ptnp11 are genes that are responsible for the creation of the chambers. Heterozygous mutations (mutation of a single allele) in these genes can cause the defect. It is not necessary for the mutation to be a loss of function mutation; even when the dosage of the gene was reduced, they observed the same phenotype. So this suggested that by raising the dosage of the genes, it would be possible to reverse the defect. 

To determine the cytoplasmic polarity, anterior side had Mex-5 protein at a higher concentration. The protein would undergo redistribution across the cytoplasm. Par-1 (posterior) phosphorylates MEX-5 and it speeds up the diffusion rate and so it is rich in the anterior side. They proved that Par-1 is necessary and sufficient by doing knockdowns of Par-1 alleles. Mex-5 had a larger complex which were more sluggish in anterior side comparison to the posterior side. The smaller complex diffused much faster from posterior on to the anterior. In terms of a model, this was described as Par-1 phosphorylating the Mex-5 to turn it into the fast species to increase the diffusion rate. 

Scientists have discovered two new species of electric eels and one of them can deliver a shock greater than the highest recorded shock from eels at 650 volts. This new species can deliver a zap at 860 volts. This discovery of a new species of electric eel is the first in over 250 years. These eels are found mostly in the Amazon rainforest. It is in this region where the scientists were able to discover these two new species of eels. To determine if the two eels were the same species, the scientists had to look at the bone structure. Doing so, they were able to determine differences in the bones and were able to accureately confirm that the two eels were different species. 

To determine if there are different sized trees in different habitats we measure the diameter at breast height (dbh) of trees on a north facing slope, south facing slope and a flat. Each location was at the Mount Holyoke Range in Amherst, Massachusetts. Each site differed in steepness and direction of slope, but not longitude of latitude. The sites were located near a point on the ridge referred to as “The Notch.” This location is also where highway 116 crosses the notch. At each site, the dbh (measured to the nearest 0.1cm), and the species of each live adult tree was measured.

Flight is one of the most involved adaptations an organism can have. What that means is that when an organism is on the evolutionary path to flight, everything else about that organism's morphology/lifestyle must change to accommodate the ability to fly. The bones must become lightweight, and habitat is most likely at a high altitude. Organisms evolving for flight have to make themselves as light as possible, meaning that heavy feathers are not a good option. The body must become streamlined in order to get the best possible flying efficiency, or face losing energy to fight additional air resistance from a non-aerodynamic body. Flying has only evolved once in mammals: the bat. The bat has a lightweight skeleton with long, thin arms that provide the framework for their wingspan. Unlike most flying animals, their eyesight can actually be very poor, and some species of bats rely on echolocation to fly around and locate prey. Flying is an all-in, evolutionary commitment, and a lifestyle that has been lived out successfully by many thousands of animals.

The steepness of a slope is an abiotic factor of the microclimate and habitat of that area. Slope aspects such as potential energy income can differ between steeper and less steep slopes (Méndez, Meave, Zermeño, Ibarra, Woods, 2016). Significant difference between individual sizes of vegetation can be found on different slopes. Although this can be due to the south facing slopes getting higher incidence of solar radiation, it could also be due to the potential energy income of larger trees on a slope versus smaller trees. If this is the case then both north and south facing slopes should have smaller trees if the slope is steeper. The larger trees of the same species are generally older than the smaller trees of the same species and this can idea can help make an inference on mortality rates of a species if there are more small trees in a given area than large ones.

The domestication of animals for human use/companionship was a very long process. Since humans began forming civilizations and societies, many animals chose to stay close to human settlements to feed on food scraps that were left behind or carelessly placed. This recruited unwanted rodents to settlements that would not only eat people's food supplies, but bring disease with them. People started to notice that cats were very good at catching and killing bothersome rodents, and would entice them with food into living with or near them. Most domestication processes begin like this, with the animal in question providing a benefit for humans and in turn being rewarded with food or shelter. 

The overall objective of our proposal is to create a phylogenetic tree to determine the reliability of HOXC genes as an indicator of phylogeny. By aligning the sequence, the genes will become easy to compare and allow for the creation of a phylogenetic tree, as proposed. The sequencing data can also be used to determine how conserved the HOXC gene is. By understanding the evolutionary and genetic differences of HOXC genes between different species, the function of HOXC genes, which are currently unknown, can be better understood. The creation of a phylogenetic tree will allow for the determination of reliability of using HOXC genes as an indicator of phylogeny. If the phylogenetic tree proves to be reliable, this would be a phylogenetic tree of vertebrates that can be used in order to trace the evolutionary history of vertebrates. If new species were to be found, its HOXC gene can be sequenced to determine its phylogeny accurately.

When an embryo is 2 weeks old, the heart muscles know their fate and they rearrange themselves in a crescent shape. Cells go to specific places and act as progenitors to form different parts like the atria, ventricles. By the third week, a tube forms that starts beating that later becomes the right ventricle. Other cells become the left ventricle. As time goes by the cells become more specific in terms of location. Newborns usually present problem only in a localized area, example, they could be born with all the chambers completely intact, but missing the right ventricle. They must have had a mutation in the cells responsible for the right ventricle that caused such a phenotype. Animal models such as chick, mouse, zebrafish embryos etc have been used to understand this process on a molecular level. However, animal models were difficult to study for very early stages. Thus, induced pluripotent stem cells became handy in order to study such preliminary phases. These cells mimic the cardiomyocytes in vivo. Together with stem cells in a dish and animal models, it was possible to understand the gene networks that chalk out the map for cardiac fate. His team was able to figure out the key components in the gene network: the Notch1, Gata4, Tbx5, Nkx2.5 and Ptnp11 are genes that are responsible for the creation of the chambers. Heterozygous mutations (mutation of a single allele) in these genes can cause the defect. It is not necessary for the mutation to be a loss of function mutation; even when the dosage of the gene was reduced, they observed the same phenotype. So this suggested that by raising the dosage of the genes, it would be possible to reverse the defect.