Question

the pedigree below tracks the presence of dimples through a family’s generation. having dimples is an autosomal dominant trait. if individual iii-3 married a woman who was heterozygous for dimples, what is the percent chance their children will have dimples? a 0% b 25% c 75% d 100%

Explanation:

Step1: Determine Genotype of III-3

Dimples are autosomal dominant (let allele be \( D \) dominant, \( d \) recessive). Individual II-1 has no dimples (\( dd \)), II-2 has dimples. Their child III-1 has no dimples (\( dd \)), so II-2 must be \( Dd \) (since she passed \( d \) to III-1). III-3 has dimples; from II-1 (\( dd \)) and II-2 (\( Dd \)), III-3's genotype: he gets \( d \) from II-1, so to have dimples, he must be \( Dd \) (because \( dd \) would be no dimples). So III-3 is \( Dd \).

Step2: Determine Genotype of Spouse

Spouse is heterozygous: \( Dd \).

Step3: Set Up Punnett Square

Cross \( Dd \times Dd \). The Punnett square has gametes \( D, d \) from each.

	\( D \)	\( d \)
\( d \)	\( Dd \)	\( dd \)

Step4: Calculate Probability of Dimples

Dimples are dominant, so \( DD \), \( Dd \), \( Dd \) have dimples (3 out of 4). \( \frac{3}{4} = 75\% \).

Answer:

c. 75%