Kaplan Nursing Entrance Practice Exam

What type of inheritance pattern does color blindness exhibit?

1. Autosomal dominant

2. Autosomal recessive

3. Sex-linked recessive

4. Codominance

The correct answer is: Sex-linked recessive

Color blindness is primarily inherited as a sex-linked recessive trait, which means that the gene responsible for this condition is located on the X chromosome. Since males have one X and one Y chromosome, a single recessive allele on their X chromosome will result in color blindness because they do not have another X chromosome to potentially provide a normal allele. In contrast, females have two X chromosomes; thus, they must inherit two copies of the recessive allele (one on each X chromosome) to express the condition. If they have only one copy of the recessive allele, the normal allele on their other X can compensate, allowing them to be normal vision while being carriers. This unique pattern of inheritance explains why color blindness is more prevalent in males than in females, as they need only one affected X chromosome to express the trait, while females need two affected X chromosomes. Other inheritance patterns such as autosomal dominant or autosomal recessive are not applicable here, as they do not involve the sex chromosomes in the same manner. Codominance involves the expression of two different alleles in a heterozygous individual, which does not relate to the mechanism of color blindness inheritance. Understanding this sex-linked recessive pattern is crucial for nursing professionals when considering genetic conditions