In humans, oculocutaneous (OCA) albinism is a collection of autosomal recessive disorders characterized by an absence of the pigment melanin in skin, hair, and eyes. That is, normal pigmentation (A) is dominant over albino characteristics.

For this question, assume the phenotype is determined by a single gene with two alleles. If two people have normal pigmentation, what possible phenotypes may be observed in their offspring?

Question

Biology

Marlie Shelton

30 March, 20:45

In humans, oculocutaneous (OCA) albinism is a collection of autosomal recessive disorders characterized by an absence of the pigment melanin in skin, hair, and eyes. That is, normal pigmentation (A) is dominant over albino characteristics.

For this question, assume the phenotype is determined by a single gene with two alleles. If two people have normal pigmentation, what possible phenotypes may be observed in their offspring?

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Answers (1)

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Josephine Valencia · Answer 1

The offspring may have: normal pigmentation or may have albinism.

Explanation:

If the person has normal pigmentation, then his possible genotype can be AA or Aa. Since both the parents have normal pigmentation, then there could be three cases of combination, Case 1: Both the parents have AA genotype. Case 2: One parent is AA and other one is Aa. Case 3 : Both parents are Aa.

In case 1:

AA x AA

will produce all offsprings with genotype AA; normal pigmentation.

In case 2:

AA x Aa

has 50% chance of producing offsprings with genotype Aa and 50% chance of producing offsprings with genotype AA. Phenotype of offsprings in both cases will be normal.

In case 3,

Aa x Aa

has 25% chance of producing offsprings with genotype AA, 50 % chance of producing offsprings with genotype Aa and 25% chance of producing aa genotype.

Offspring with genotype AA or Aa will have normal pigmentation and offsprings with genotype aa will be albino.