Question

1. brown hair is dominant to blonde hair. cross a woman who is heterozygous for brown hair with a man who is heterozygous. what percentage of their children will have brown hair?
2. cross a man who is homozygous for brown hair with a woman who is heterozygous for brown hair. what percentage of their children will be blonde?

Explanation:

Step1: Determine the genotypes

Let \( B \) represent the allele for brown hair (dominant) and \( b \) represent the allele for blonde hair (recessive).

• For problem 1: The woman is heterozygous (\( Bb \)) and the man is heterozygous (\( Bb \)).
• For problem 2: The man is homozygous (\( BB \)) and the woman is heterozygous (\( Bb \)).

Step2: Create Punnett squares

• Problem 1:

	\( B \)	\( b \)
\( b \)	\( Bb \)	\( bb \)

• Problem 2:

	\( B \)	\( B \)
\( b \)	\( Bb \)	\( Bb \)

Step3: Calculate probabilities

• Problem 1:
• Genotypes: \( BB:Bb:bb = 1:2:1 \)
• Brown - haired (\( BB \) or \( Bb \)): \( \frac{3}{4}=75\% \)
• Problem 2:
• Genotypes: \( BB:Bb = 1:1 \)
• Blonde - haired (\( bb \)): \( 0\% \)

Answer:

1. \( 75\% \)
2. \( 0\% \)