Chapter 12.1, Problem 4R

Summary Introduction

To analyze:

The following, based on the given pedigree of congenital cataracts in the humans,

1. Whether the cataracts are inherited as the autosomal recessive or the dominant trait.

2. The chance that the person 5 in the second generation, would produce a girl with cataract.

Given:

The following pedigree chart represents the inheritance of congenital cataracts, which is a rare mutant phenotype in humans (Figure 1). The cataract is represented as black symbols, while the normal phenotype is represented as white.

Figure 1: A pedigree chart representing the inheritance of cataract in humans.

Introduction:

The chromosomes other than the sex-chromosomes are called as autosomes. They do not participate in the determination of sex. The disorders of autosomes affect the male and female progeny alike. The results of offsprings are not biased between male and female. These autosomal disorders can be recessive or dominant. When the presence of one affected allele results in a diseased condition, the trait is autosomal dominant. The case where both the alleles are required to express a diseased condition, then those alleles are called as autosomal recessive alleles.