Question

Consider two populations, I and II, with initial frequencies of q0=0.8 and q0=0.2, respectively. What are the change in gene frequency after one generation and its ultimate value in population I if migration occurs from population II to I at the rate of 3% every generation? How many generations of continuous migration it will take to halve the gene frequency of population I?

Answer 1

We are going to use the hardy Hardy-Weinberg law ,considering the two populations, I and II, with initial frequencies of q0=0.8 and q0=0.2, respectively. The hardy Hardy-Weinberg law applies basic rules to calculate genotype frequencies from allele frequencies. It states that allelic frequencies remain constant from one generation to the next.if the allelic frequencies of alleles A and a in the initial population were p = 0.8 and q = 0.2, the allelic frequencies in the next generation will remain p = 0.8 and q = 0.2. The conditions for Hardy-Weinberg equilibrium are rarely found in action in nature, although they are essential for studying population genetics.If a population differs from assumptions by Hardy-Weinberg, it is proof that there are at least any of the criteria is not met. Then researchers will decide why allelic frequencies change, and thus how evolution affects the population.

For example, for the population mentioned previously with p value of 0.8 and q value of 0.2, let' s mixed the gametes with 80% of which are B and 20% are b.Therefore, on the the sperm ,we have the given proportions of the two alleles (0.8 of allele B and 0.2 of allele of b ,freely mixing with the eggs , which have the alleles in the same proportions (0.8 of B and 0.2 of b).

The probability of an B sperm meeting an B egg is 0.8 x 0.8 = 0.64. The probability of an B sperm meeting an b egg is 0.8 x 0.2 = 0.16. The probability of an a sperm meeting an B egg is 0.8 x 0.2 = 0.16. The probability of an a sperm meeting an b egg is 0.2 x 0.2 = 0.04.

Therefore in the following generation, we would expect to have the following proportion of genotypes:

• 0.64 BB
• 0.32 Bb
• 0.04 bb .Therefore allele frequencies are the same as in the parental generation.Then we see all this with spontaneous mating, no collection, no migration and mutation, and a population significantly large to overlook the impacts of random chance, the proportion of alleles in a population remains the same throughout parent to child.