Question

In 1783, a British sailing ship crashes on an island in the South Pacific. 100 individuals survive, only to discover that the island is already inhabited by a native population of 300. With no hope of returning home, they join the local population.

A) In Great Britain, the allele frequency for blue eyes (b) is 0.8. If the native population is true-breeding for brown eyes (B, which has complete dominance over b), what is the new allele frequency for this mixed population? Assume that the allele frequency of the sailors matches the population of Great Britain, and assume random mating.

B) If the population breeds to Hardy-Weinberg equilibrium, what are the expected genotype frequencies of BB, Bb, and bb? What are the expected phenotype frequencies?

C) 100 years later, you arrive on this island to study the local population. This population has increased to 2000 individuals. 1,940 have brown eyes, 60 have blue eyes. Has this population maintained Hardy-Weinberg equilibrium? SHOW ALL WORK.   

D) What are the new allele frequencies?

E) While you are on the island, an outbreak of river blindness (a roundworm infection of the eye) occurs. For some reason, this particular strain of worm prefers to infect brown eyes. This gives brown eyed individuals a fitness of 0.8 relative to blue eyed individuals. Calculate the mean fitness (W).

F) If there are 2000 individuals in the next generation, what phenotype ratios would you expect in the next generation, considering the effect of river blindness?

Answer 1

the native population was 300. the added population of sailor is 100. the total population become 400

native population have brown eyes, which is dominant=BB

the sailors have blue eyes, which is recessive=bb

A) given the allele frequency of b(q)=0.8

allele frequency of B(p)=

p+q=1

p=1-0.8

p=0.2

thus allele frequency for B=0.2

allele frequency of Bb is 20.20.8

=0.32

C) total individual are=2000

brown eye=1940

blue eyes=60

the percentage of blue eye= 60100/2000

=3%

the allele frequency of blue eyes(bb)=0.03%

thus allele frequency of b =0.17

the allele frequency of brown eyes=0.97%

allele frequency of B=0.98

the total frequency is above one thus, it does not follows the equilbrium law