In the attached figure, I have drawn a pedigree illustrating a family with an au

Question

In the attached figure, I have drawn a pedigree illustrating a family with an autosomal recessive disorder. Everyone's phenotype is depicted correctly, but I have only given you information about the genotypes for II-3 and III-4. There are a number of people in the pedigree who are unaffected carriers. From what you know about autosomal recessive pedigrees, please identify all those people who must be unaffected carriers. Don't tell me all who might be a carrier--just tell me who MUST be a carrier. No need to explain-just list the carriers using the proper 2-number system of identification.

Explanation / Answer

The disorder expressed in the II3 male. This disorder is expressed in the male only and skipped in some generation. It is not an autosomal recessive disorder, it is a X linked recessive disorder. If it is autosomal it will expressed irrespective of male and female. The defected allele present in the one X chromosome in the I-2 Female, thus it is not expressed due to presence of a wild type allele. But it expressed in male as only one X chrosome is there and the male received the defected X allele. It again expressed in the III4 male which means he received the defected allele from his mother II-4.

So, I-2 and II-4 both are the carrier of the disorder.

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