Chapter 11, Problem 17A

Summary Introduction

To explain:

Whether a male could be heterozygous for red- green color blindness

Introduction:

Traits that are controlled by genes located on sex chromosomes; X chromosomes in particular are called sex- linked traits or X- linked traits. Since males have only X chromosome, they are affected by recessive X- linked traits more often than females. Females usually do not express the recessive trait as other X chromosome will mask the effect of the recessive trait.

Answer to Problem 17A

A male cannot be heterozygous for red- green color blindness because males have only one X chromosome. If they have the recessive allele on X chromosome they will have red- green color blindness.

Explanation of Solution

Red- green color blindness is a recessive X- linked trait. A male person will suffer from red- green color blindness if he has the recessive allele on X chromosome. He cannot be heterozygous for color blindness as there is only one X chromosome in a male person. A female will suffer from red- green color blindness only if she is homozygous for the recessive gene. She can be heterozygous for red- green color blindness as there are two X chromosomes in females but will not suffer from the disorder. Instead a heterozygous female will be a carrier for red- green color blindness.