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Embed code for: assignment 2 (simbio)
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Genetic evolution is stimulated by genetic variation, evolution in the genome, speciation, adaptation and genetic change within populations that will be beneficial to the species. Typically, from a molecular point of view, there consists of one dominant and one recessive allele that can oscillate in frequency within populations due to external/internal influences i.e. predation and mutation. So, in most cases, dominant alleles will be favored over recessive alleles and therefore over a period of time, the population will shift towards the dominant side and essentially have the recessive allele disappear (hypothetically). However, according to the Hardy-Weinberg principle, frequency does not change over time if it’s a large population, no mutations, random mating, no selection and no gene flow. So in this experiment, Hardy-Weinberg’s principle will be tested out on a pig population that displays a black (dominant) and brown (recessive) pigmentation. The main focus will be on whether the recessive allele will change or disappear over time.
There will be two separate populations where one pigmentation is significantly larger in number of individuals than the other. For the first population, it will have the black (B) allele frequency low and the brown (W) allele frequency high. For the second population, it will be the exact opposite; high frequency for the black pigmentation and low frequency for the brown pigmentation. There will be no external or (assuming) no internal interference that will alter the frequency because the focus is on whether the recessive allele will fluctuate or disappear on its own. This experiment will be conducted over a course of ~350 months.
Figure 1 and 2 had taken place in environment 1 (E1), where the recessive allele W (brown pigmentation) was larger in population size than the dominant allele B (Black pigmentation). Figure 3 and 4 had taken place in environment 2 (E2), where the dominant allele B was larger in population size than the recessive allele W. Also in each allele has no selective advantage or disadvantage so the birth and death rate for each individual are indiscriminate.
Figure 1: Frequency of Allele B in E1 Figure 2: Frequency of Allele W in E1
Figure 3: Frequency of Allele W in E2 Figure 4: Frequency of Allele B in E2
In all the figures, the x axis is frequency of the particular allele while the y axis is the time (month) the experiment had partaken in. In each figure, it displays that the frequencies of individual alleles did not fluctuate over the course of 354 months. In figure 1, The initial frequency was 0.20 and the final frequency was 0.18. In Figure 2, the initial allele frequency was 0.80 and the final frequency was 0.82. In figure 3, the initial frequency was 0.20 and the final frequency was 0.25. In figure 4, the initial frequency was 0.80 and the final was 0.75.
Before conducting the experiment, the prediction was that the allele frequencies in the population will relatively stay the same and the phenotypes will be stabilized but there is no set ratio to correlate with it. The results were accurate to the prediction because there was no differentiation between the allele frequencies in separate environments. In both populations, each allele was given the advantage of having more individuals than the other over a course of time and ultimately, the frequencies barely changed whether it was dominant or recessive. Although there was a fluctuation of frequencies in the genotype and phenotype of the pigmentations, the allele itself remained the same. So if a species contains a recessive trait, doesn’t necessarily mean that it will essentially go extinct over a course of time.