Question

Question 1: Consider a biallelic locus in an annual plant population. You observe the allele frequencies of allele A and allele T are equal to 0.4 and 0.6 in 2010, respectively.

A) Calculate the heterozygosity (H) of this locus in 2010, assuming the population mating is at random.

B) What is the expected frequency of allele A in 2020?

C) If the effective population size of this population is equal to 1,000, what is the expected heterozygosity of this locus in 2020?

D) If the effective population size is equal to 10 instead, what is the expected heterozygosity in 2020?

E) Based on your calculation, explain why genetic diversity is typically very low in endangered species.

Question 2: The observed heterozygosity (H) of a microsatellite is equal to 0.2% in a diploid population, and the mutation rate (per generation) at this microsatellite locus is equal to 2 x 10^-8.

A) Estimate the effective population size of this population.

B) The census population size of this population is 10⁶. Name two distinct processes that can contribute to the mismatch between the census population size and the effective population size.

Question 3: Suppose there are two annual plant species (A and B). Species A lives in a stable environment and has a constant census population size of 1,000. Species B lives in an unstable environment alternating between dry and wet years. Species B’s census population size is 200 in dry years and 1,800 in wet years. The frequencies of the dry and wet years are equal.

A) What is the effective population size of species A?

B) What is the effective population size of species B?

C) Assume the two species are similar in genome size and mutation rate, which species do you expect to have a higher level of heterozygosity? Why?

Question 4: Suppose a population has an effective population size of 50. In one generation, the average heterozygosity (averaged across loci) is reduced from 0.5 to 0.42. Is the population mating at random? Why?

Question 5: What is the effective population size in a population in which each breeding male controls a harem of 10 females, and the total population consists of 400 males and 400 females?

Answer 1

Answer:-- according to Hardy Weinberg law ,

p2+ 2pq+ Q2 = 1

Where p and q are allele frequency of dominant and recessive allele In a locus.

In question p= A , q= T

2pq denotes heterozyogosity .

Here allele frequency for

T =0.6 , A= 0.4

Heterozygosity of the biallelic locus in 2010 , considering random mating = 2pq

= 2 AT

=2×0.6×0.4

=0.48

B) Answer:- Expected allele frequency of allele A in 2020 will be 0.4 as there is no mention about external factors which may cause change in allelelic frequency so according to Hardy Weinberg Equilibrium law allele frequency will remain constant in absence of any external disturbing factors like mutation, natural selection etc.

C) answer:- we have calculated the heterzygous allele frequency in population in question A and found as 0.48 i.e

In percentage it is 0.48×100%

= 48%

Heterzygous allele frequency for per 100 people is 48. Hence when population is 1000 it will be ---

= 48/100× 1000

= 480.

Hence expected heterzygousity for this locus is 480 people if effective population size is considered as 1000 in 2020.

D) Answer:- If effective population size is equal to 10.

Then expected heterzygousity= 48/100 × 10

= 4.8 people .

E) Answer:- Based on calculation of heterzygousity in population it is clear that smaller the population lower the genetic diversity.

In endangered species , population become too small that they are prone to extinction hence genetic diversity is very low in those animal.

Q 2.A. answer:- given heterzygousity of microsatellite is 0.2%

In frequency it is 0.2/100 = 0.002

Effective population size= genetic diversity/ 4× mutation ration

= 0.002 / 4× 2×10-8 ( here -8 is exponential power of 10)

=2.5 × 104( here 4 is exponential power of 10)

= 25000

Hence estimated effective population size is 25,000.

B. Answer:- Two processes that can create mismatch between census population size and effective population size are ---- bottleneck effect and fragmentation event between population.

Q.4.answer:- the decreases in heterozyogosity frequency from 0.5 to 0.42 indicates their inbreeding which reduces diversity in population . Hence the population is mating non randomly.