Question

Unattached earlobes is a dominant trait, E. A parent who is homozygous for unattached earlobes is crossed with a parent who is homozygous for attached earlobes. What is the genotypic ratio of their offspring?

Answer 1

Answer: The correct answer is -

The genotypic ratio of the offsprings of given parents is 100% Ee (Heterotrozygous dominant that exhibit unattached earlobes).

Explanation:

As per the given information in the question, unattached earlobe is a dominant trait over the attached earlobe, which is a recessive trait.

Dominant trait (expressed by capital letter allele like E for unattached earlobes) masks the expression of recessive trait (that is  expressed by small letter allele such as e for attached earlobes).

Genotype of parents is-

EE (homozygous dominant) that will form 'E' and 'E' gametes.

ee (homozygous recessive) that will form 'e' and 'e' gametes.

When these parents are crossed, they will produce-

     EE × ee

=Ee, Ee, Ee, Ee

Thus, all offspring are heterozygous dominant (Ee) that will exhibit unattached earlobe trait due to the presence of dominant allele (E) in them.

Answer 2

Punnett Square time!!
The genotypic ratio for their offspring is 100% Ee (heterozygous)