You have been tracking a population of birds in the jungle a

You have been tracking a population of birds in the jungle and over several generations observed the following genotype frequencies for a given locus, B : 12% BB, 28% Bb, and 60% bb. The climate changed abruptly and resulted in the death of all homozygous recessive birds. In the next generation, the recessive homozygotes died shortly after birth. What percentage of all newborn bird died ? (Hint: You will need to recalculate the genotype frequencies after a portion of the population died and also use the product rule to calculate the proportion of matings that could lead to homozygous recessive individuals in the next generation.) Please show all work.

The correct answer is 12.25% and I cannot figure out how to arrive at this answer

Solution

Answer: A population of birds in the jungle and over several generations observed the following genotype frequencies for a given locus, B : 12% BB, 28% Bb, and 60% bb.

Due to some problem all homozygous recessive individuals died. Therefore, post-genetic drift frequencies would be:

BB : (12 /40) x100 = 30

Bb : (28/40) x 100 = 70

bb : 0

Suppose the population is randomly mating,

Case 1 BB finding a mate with BB genotype- Chances: 9/100

NO offspring would have genotype bb

Case 2 BB finding a mate with Bb genotype- Chances: 42/100

NO offspring would have genotype bb

Case 3. Bb finding a mate with Bb genotype

Probability = 49/100 = 0.49

Probability of occurrence of genotype bb is

Bb x Bb

Gametes B b

B BB Bb

b BB bb

probability = 1/4 of 49%

=12.25% of bb genotype would be produced and will die immediately after birth.