Question

reflection: this will test your understanding of punnett squares. challenge: brown eyes in humans are dominant to blue eyes. a brown - eyed man, whose mother was blue - eyed, marries a brown - eyed woman whose father had blue eyes. what is the probability that this couple will have a blue - eyed child?

Explanation:

Step1: Define alleles

Let \(B\) = dominant brown eye allele, \(b\) = recessive blue eye allele. Blue eyes require \(bb\).

Step2: Find man's genotype

Man's mother is \(bb\), so he inherits \(b\) from her. He has brown eyes, so his genotype is \(Bb\).

Step3: Find woman's genotype

Woman's father is \(bb\), so she inherits \(b\) from him. She has brown eyes, so her genotype is \(Bb\).

Step4: Set up Punnett Square

Cross \(Bb \times Bb\):

$$\begin{array}{c|cc} & B & b \\ \hline B & BB & Bb \\ b & Bb & bb \\ \end{array}$$

Step5: Calculate blue-eyed probability

Count \(bb\) (1 out of 4 outcomes). Probability = $\frac{1}{4}$.

Answer:

$\frac{1}{4}$ or 25%