AP BIOLOGY

HEREDITY

LAW OF DOMINANCE

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

A student’s mother is heterozygous for attached earlobes, a recessive trait. The student’s father is also heterozygous for that trait. What is the % likelihood that this student has attached earlobes?

A	0%
B	25%
C	50%
D	75%

Explanation:

Detailed explanation-1: -The answer is c) 50%. This can be visualized with a Punnett square.

Detailed explanation-2: -Final answer: There is a 25% chance that the next child will have attached earlobes.

Detailed explanation-3: -If a person has a free earlobe, then its genotype would be either UU or Uu. If a person has an attached earlobe then its genotype would be uu. So, if parents (male as well as female) have free earlobes and offspring have attached earlobes, then surely both parents would be heterozygous for this trait.

Detailed explanation-4: -Autosomal recessive inheritance This means a child has to get 2 copies of the gene that causes albinism (1 from each parent) to have the condition. If both parents carry the gene, there’s a 1 in 4 chance that their child will have albinism and a 1 in 2 chance that their child will be a carrier.

There is 1 question to complete.