pleiotropii

Pleiotropy refers to a phenomenon in genetics where a single gene influences multiple, seemingly unrelated phenotypic traits. Instead of controlling just one characteristic, a pleiotropic gene has a broad impact on an organism's development or physiology. This can occur for several reasons. The gene might encode a protein that is crucial for a fundamental biological process that is involved in many different aspects of an organism's life. Alternatively, the gene's product might be a signaling molecule or transcription factor that regulates the expression of many other genes.

Examples of pleiotropy are found across the biological spectrum. In humans, the gene responsible for Marfan syndrome is a classic illustration. Mutations in this gene lead to defects in connective tissue, affecting skeletal structure, the cardiovascular system, and the eyes. Another well-known example is phenylketonuria (PKU), an inherited metabolic disorder caused by a mutation in a gene that produces an enzyme involved in breaking down the amino acid phenylalanine. Without this functional enzyme, phenylalanine builds up in the body, leading to intellectual disability, seizures, and lighter skin pigmentation.

In plants, the gene responsible for dwarfism in pea plants, studied by Gregor Mendel, also affected the color of the axil leaves. Understanding pleiotropy is important for predicting the full consequences of genetic mutations and for comprehending the complex interplay of genes in shaping an organism's traits. It highlights that genes do not always operate in isolation but can have far-reaching and diverse effects.