Question

For humans, an inherited form of blindness called retinitis pigmentosum-11 results from the expression of an autosomal dominant allele. Some individuals who inherited this allele have clear vision throughout their lives while others become completely blind by thirty years of age. What is the likely explanation for this difference?

1) The allele is not fully penetrant, meaning that it does not always cause the phenotype of blindness.
2) The allele undergoes somatic mutations in some individuals, leading to blindness.
3) The allele interacts with other genetic factors or environmental factors to cause blindness.
4) The allele is only expressed in certain tissues or cells, leading to blindness.

Answer 1

The likely explanation for the variation in expression of retinitis pigmentosum-11 among individuals with the dominant allele is due to incomplete penetrance and possibly interactions with other genetic or environmental factors.

Step-by-step explanation:

The variation in the expression of retinitis pigmentosum-11, which can cause differing levels of blindness even though it's an autosomal dominant allele, is likely due to the allele not being fully penetrant. This means a person may inherit the allele without developing the phenotype of blindness. An example of this would be in cases where the presence of a single functional allele is sufficient to prevent the manifestation of the disease, as seen with other genetic traits such as brown eye color.

Environmental factors or interaction with other genes could also influence the expression of retinitis pigmentosum-11, as the phenotype may emerge from a complex interplay between multiple genetic and external variables. This multigenic and environmental contribution could result in differing levels of disease severity among individuals who carry the dominant allele.