Kaplan Nursing Entrance Practice Exam

What is the relationship between X-linked inheritance and color blindness?

1. Only females can be color blind

2. Boys inherit the gene only from their fathers

3. The gene is located on the X chromosome

4. It is a dominant trait

The correct answer is: The gene is located on the X chromosome

The correct answer highlights that the gene responsible for color blindness is located on the X chromosome. Color blindness is an example of X-linked recessive inheritance, where the gene that causes the condition resides on the X chromosome. In humans, males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). If a male inherits an X chromosome carrying the color blindness gene, he will express the trait because there is no second X chromosome to potentially carry a normal allele. In contrast, a female would need to inherit the gene from both parents to be color blind, as she can have one normal allele on her other X chromosome that compensates for the affected one. This relationship emphasizes the importance of the X chromosome in the inheritance of color blindness.