Question

question 2
dear abby,
on march 18, 1995, ann landers printed a letter from a man who was upset because he and his wife both brown - eyed had a \gorgeous 7 month old daughter with the brightest blues eyes i have ever seen.\ the father continues, \although i love my daughter with all my heart, i still have some doubts that she is my biological child when i look into her beautiful blue eyes.\
what are the chances that their second child will have blue eyes? (hint: show the process on a piece of paper by conducting a simple punnet square. brown eyes are dominant, blue are recessive).
a 0
b 25%
c 50%
d 100%

Explanation:

Step1: Determine parental genotypes

Since both parents have brown - eyes and they had a blue - eyed child, their genotypes must be heterozygous. Let B represent the dominant brown - eye allele and b represent the recessive blue - eye allele. So the parents' genotypes are Bb.

Step2: Set up Punnett Square

The possible gametes from each parent are B and b. The Punnett Square has 4 boxes. The top row has B and b (gametes from one parent), and the left - hand column has B and b (gametes from the other parent).

Step3: Fill in Punnett Square

When we fill in the Punnett Square: BB, Bb, Bb, bb.

Step4: Calculate probability

The genotype bb results in blue eyes. Out of 4 possible genotypes, 1 is bb. So the probability is $\frac{1}{4}$ or 25%.

Answer:

B. 25%