Question

Attached earlobes are a recessive trait in humans. in the tree below, people with attached earlobes are shaded in. which best describes the person labeled X in the tree?
A) a male with one recessive allele
B) a female with no recessive alleles
C) a female with one recessive allele
D) a male with no recessive alleles

Answer 1

Answer:

The correct option is A) a male with one recessive allele

Explanation:

As we can depict, the offsprings are formed by a cross between a homozygous recessive parent and a heterozygous parent.

The outcomes of such a cross will be:

      r            r

R   Rr          Rr

r    rr            rr

The results from the cross show that the offsprings from such a cross will either have both recessive alleles and will have attached earlobes or they will be heterozygous dominant having unattached ear lobes.

As we can see from the pedigree, the person labelled X is not shaded hence it cannot carry the alleles rr. So, the person is heterozygous carrying one dominant and one recessive allele.