Chapter 17, Problem 1QC

Summary Introduction

To discuss:

The possibility that whether the unaffected female can have female offspring with red-green colorblindness.

Concept introduction:

The traits can be defined as the phenotypic characteristics that are coded by the genes. The genes coding for the traits can be present in X chromosome, Y chromosome or the autosomes. The traits are inherited as autosomal recessive, autosomal dominant, X-linked recessive, X-linked dominant traits or Y linked traits. There are certain traits which are influenced or limited to one sex. The red-green colorblindness is an X-linked recessive trait.

Explanation of Solution

Pictorial representation:

Fig. 1: The possible genotype and phenotype of the progeny produced by the unaffected female.

Fig. 1: The possible genotype and phenotype of the progeny produced by the unaffected female.

Explanation:

The X-linked recessive diseases are expressed in males who have one mutant allele, as the males have only one X chromosomes. The females having two mutant alleles of X-linked disease will be affected by it. The heterozygous females (carrying one mutant allele) will be normal but they will be the carrier.

If the father of the unaffected female would be affected, then all the daughters will be the carrier of the trait. A colorblind father will have all the carrier daughters. If the carrier female marries a colorblind man, then half of the daughters will be affected.

Conclusion

In case, if the father of the unaffected female would have been affected, then all of his daughters would be carrier. If the carrier female marries a colorblind man, then half of her daughter will be affected.