What constitutes a major effect of pleiotropy in genetic disorders?

Pleiotropy refers to the phenomenon where a single gene mutation affects multiple, seemingly unrelated phenotypic traits. This is a significant concept in genetics because it highlights how one genetic change can have widespread and varied effects on an organism's biology.

In the context of genetic disorders, a major effect of pleiotropy is indeed illustrated by a single mutation causing multiple phenotypic manifestations. For example, certain mutations in the gene responsible for cystic fibrosis lead to a range of symptoms affecting the lungs, pancreas, and even sweat glands, all stemming from the same genetic defect. This exemplifies how alterations in a single gene can lead to diverse clinical presentations, reinforcing the complexity of genetic influences on health and development.

The other options reflect different concepts in genetics. Multiple mutations leading to a single phenotype typically describes a situation known as genetic heterogeneity, where various mutations can cause the same disorder. Environmental influences altering gene expression points to the field of epigenetics, where external factors impact how genes are expressed without changing the underlying DNA sequence. Finally, age-related changes in phenotype examine how physical or functional changes can occur over time due to a combination of genetic and environmental factors, but do not specifically relate to the concept of pleiotropy. Understanding the significance of