In humans, long eyelashes (L) are dominant over short eye lashes (l); while attached earlobes (e) are recessive to unattached ear lobes (E). A man heterozygous for both eye lashes and earlobes married a woman that is homozygous for long eyelashes and has unattached ear lobes but carries the recessive allele for attached earlobes. Show all of your work!

Give the genotypes of each of the parents.

Man - Woman -

What are the possible gametes for each parent?

Man - Woman –

1) Genotype of man- LlEe

Genotype of woman- LLEe

2) Possible gametes produced by man- LE, Le, lE and le

Possible gametes produced by woman- LE, Le, LE and Le

Explanation:

This question involves two different genes with one coding for length of eye lashes and the other for earlobes formation in humans. The long eyelashes allele (L) is dominant over the short eyelashes allele (l) in the first gene while unattached earlobe allele (E) is dominant over the attached earlobe allele (e) in the second gene.

According to the question, a man heterozygous for both eye lashes and earlobes will possess a genotype LlEe. Note that, heterozygous means containing two different alleles (L, l and E,e in this case). Hence, if the man is heterozygous for both genes, it means he possesses two different alleles for the two genes (LlEe).

A woman that is homozygous for long eyelashes (LL) and has unattached ear lobes but carries the recessive allele for attached earlobes (Ee) will have genotype: LLEe. Homozygous means contain same alleles. The woman contains same alleles (homozygous) for long eyelashes (LL). She has unattached earlobes but carries the allele for attached earlobe, this means that she is heterozygous for the second gene (Ee). Hence, she will possess a LLEe genotype.

For Question 2, according to the Law of Independent assortment proposed by Mendel, the alleles of a gene will separate into gametes independently of the alleles of the other gene. This means that in a random manner, a gamete will contain one allele of the each gene.

Based on this, a man with genotype LlEe will undergo meiosis to produce four possible allelic combinations of gametes (sperms) viz: LE, Le, lE and le

The woman with genotype: LLEe, following the same principle of independent assortment, will undergo meiosis to produce the following allelic combinations of gametes (eggs): LE, Le, LE and Le.

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