Predict the potential effect of the Lyon hypothesis on the retina of a human female heterozygous for the X-linked red-green color blindness trait.

Key Concepts

Lyon Hypothesis

The Lyon hypothesis, also known as X-inactivation, states that in female mammals, one of the two X chromosomes is randomly inactivated during early embryonic development. This process ensures dosage compensation between males (XY) and females (XX) for X-linked genes. The inactivated X chromosome forms a Barr body and is largely transcriptionally silent, which can influence the expression of X-linked traits.

X-linked Inheritance

X-linked inheritance refers to the pattern of inheritance for genes located on the X chromosome. In females, who have two X chromosomes, the expression of X-linked traits can be influenced by which X chromosome is inactivated. In the case of X-linked red-green color blindness, a female heterozygous for the trait may express normal vision if the normal allele is on the active X chromosome, while the color blindness allele is on the inactive one.

Retinal Function and Color Vision

The retina contains photoreceptor cells, including cones that are responsible for color vision. In humans, the red-green color blindness trait affects the function of specific cone cells, leading to difficulties in distinguishing between red and green hues. In a heterozygous female, the random inactivation of one X chromosome can result in a mosaic pattern of retinal cells, where some cells express normal color vision while others do not, potentially leading to partial color blindness.