Question

Ethyl and Egbert are starting their family. Ethyl has free earlobes, but her mother has attached earlobes; Ethyl is not able to roll her tongue. Egbert also has free earlobes, but he is able to roll his tongue. Egbert's son from a previous marriage has attached earlobes and is a non-roller.

What are Ethyl's and Egbert's genotypes for these two genes? Fill in your answers on the answer page.

If Ethyl and Egbert have a large family, what fraction of their children to you expect to have a phenotype (for these two traits) just like their mother, Ethyl? Fill in your answer on the answer sheet, and don't forget to show your work for this problem in the appropriate space on that page.

Answer 1

In the given data Ethyl has free earlobes. Her mother has attached earlobes. It shows " free earlobes" is the dominant trait over "attached earlobes". And Ethyl is heterozygous for her free earlobes. Ethyl is not able roll her tongue.

Egbert has free earlobes. but he is able to roll his tongue. His son from a previous marriage is having attached earlobe and he is a non-roller. It shows that Egbert is having heterozygous free earlobes and heterozygous tongue-rolling traits.

Ethyl is heterozygous for free earlobes and homozygous recessive for non-rolling of tongue.

Egbert is heterozygous for free earlobes and heterozygous for tongue rolling traits.

As both Ethyl and Egbert are heterozygous for free earlobes trait, and as free earlobes trait is dominant trait

25% of their children will be homozygous dominant for free earlobes

50% of their children will be heterozygous dominant for free earlobes

25% of their children will be homozygous recessive for attached earlobes.

Ethyl is non-tongue roller - which is recessive trait.

Egbert is heterozygous tongue roller.

Then 50% of their children will be heterozygous tongue rollers and 50%of their children will be homozygous recessive for non-tongue rolling.