Case of Hardy-Weinberg Theorem dealing with Mendelian genetics

Question 1

Consider a series of island populations each founded by a single individual that is heterozygous at

a particular locus. If the alleles at this locus are neutral, and there is no mutation or migration,

describe what the variation will look like after many generations within each population. Why?

Answer:

This is the typical case of Hardy-Weinberg Theorem dealing with Mendelian genetics.

According to this theorem :allele frequencies in a population will not change from generation to

generation.

If the allele frequencies in a population with two alleles at a locus are p and q, then the expected

genotype

frequencies are p2, 2pq, and q2. This frequency distribution will not change from generation to

generation once a population is in Hardy-Weinberg equilibrium.

Question 2

Why is underdominance so rare in natural population?

Answer:

Underdominance exists in situations where the heterozygotic genotype is inferior in fitness to either

the dominant or recessive homozygotic genotype. It is rare in natural populations as it is considered

more unstable and may lead to fixation of either allele.

Question 3

Imagine a colorful population of insects. Out of 350 individuals in the population, 25% are red, 40%

are purple, and the remaining are blue. Red collaration is caused by homorygorsity of the R allele at

a single locus; blue coloration is caused by homozygously of the B allele at that locus;

heterozygotes are purple. Is this population in Hardy-Weinberg equilibrium at this locus? Show all

work.

Answer:

The genotype frequencies are:

Red: 0.25, that is 87.5 individuals

Blue: 0.35, that is 122.5 individuals

Purple: 0.4, 140 individuals

Now, to calculate the allelic frequencies we have to count the previous values