Question

In humans, sickle-cell anemia is an example of co-dominance, when considered at the molecular level. People who are homozygous dominant produce all normal-shaped hemoglobin molecules. Hemoglobin is a protein found in red blood cells that carries oxygen. People who are homozygous recessive produce all abnormally-shaped hemoglobin, which cannot carry oxygen very well. People who are heterozygotes produce some normal and some abnormal hemoglobin. If a person who is homozygous dominant for this allele produces children with someone who is heterozygous, will any of their children produce only abnormal hemoglobin? What percentage of their offspring will be homozygous versus heterozygous? Show your work.

Answer 1

Answer:

Yes, 50% homozygous vs 50% heterozygous

Explanation:

Let dominant sickle cell allele be represented by an allele A while the recessive form be represented by S.

A person that is homozygous dominant for the trait will be AA genotype.

A person that is heterozygous for the trait will be AS genotype.

A cross between the homozygous dominant and heterozygous will be:

                              AA       x       AS

The F1 offspring will be AA, AA, AS, and AS (See the Punnet's square result)

Recall that: AA produce all normal-shaped hemoglobin molecules. Hence, 50% of the offspring will produce all normal-shaped hemoglobin.

Also, the ratio of homozygous to heterozygous offspring is 1:1, equivalent to 50% homozygous vs 50% heterozygous.

Therefore, considering the questions;

Will any of their children produce only abnormal hemoglobin? The answer is yes.

What percentage of their offspring will be homozygous versus heterozygous? The answer is 50% versus 50%