Pleiotropy 🧬 – One Gene, Many Faces

Sometimes a single gene can shape several visible traits in an organism. Genes with this super-power are called pleiotropic genes. When a pleiotropic gene changes, different body features change together because the gene influences shared metabolic pathways that branch out to many traits.:contentReference[oaicite:0]{index=0}

How It Works 🔄

  • One gene → multiple phenotypes (visible traits):contentReference[oaicite:1]{index=1}
  • The gene’s product (often an enzyme) sits at a key step in metabolism.
  • Any change in that product ripples through the pathway, so several traits shift together.:contentReference[oaicite:2]{index=2}

Classic Example – Phenylketonuria (PKU) 🩺

  • Culprit gene: codes for the enzyme phenylalanine hydroxylase. A mutation here causes PKU.:contentReference[oaicite:3]{index=3}
  • Main outcomes:
    • Intellectual disability (mental retardation) 🧠
    • Lighter hair and skin pigmentation 🎨
    Both effects come from one gene change!:contentReference[oaicite:4]{index=4}

Why This Matters 💡

  • Shows that predicting traits isn’t always one-gene-one-trait.
  • Helps explain how single-gene disorders create complex symptom sets.
  • Guides medical screening for hidden metabolic issues.

Important Concepts for NEET 🔑

  1. Definition of pleiotropy: one gene, many traits.:contentReference[oaicite:5]{index=5}
  2. Mechanism: gene action on shared metabolic pathways.:contentReference[oaicite:6]{index=6}
  3. Phenylketonuria (PKU): mutation in phenylalanine hydroxylase gene causing multiple symptoms.:contentReference[oaicite:7]{index=7}
  4. Clinical features of PKU: intellectual disability and reduced pigmentation.:contentReference[oaicite:8]{index=8}