Genetics and Genomics

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Examining Hemophilia A, X-linked Traits and Abnormal Chromosomes


Hemophilia A is a disorder caused by a recessive mutation in a gene on the x chromosome. You are examining a family with a son that has Hemophilia A. The father also has hemophilia A, while the mother does not.

Given the mode of inheritance, the son most likely inherited the mutant allele from


Examining​ the father, we identify that he has an allele we will designate as "allele A". In the mother, we find that she does not have a mutant allele. It is

that she could have produced an egg that contained a mutant allele.

could result in a mutant allele.

Sequencing the gene in the son yields a very strange result. The son appears to have two different alleles of the gene responsible for Hemophilia A, an "allele A" and an "allele B".

Given this datum, the son also likely has


The most likely explanation for this would be