Examples of pleiotropy in genetics.

📚 Quick Study Guide

• 🧬 Pleiotropy Defined: A single gene influences multiple distinct phenotypic traits.
• 🌟 Mechanism: Often arises because the gene product is involved in multiple biochemical pathways or affects multiple cell types.
• 🌱 Examples:
  • Cystic Fibrosis: A mutation in the CFTR gene affects lungs, pancreas, and sweat glands.
  • Phenylketonuria (PKU): A defect in phenylalanine hydroxylase affects brain development and skin pigmentation.
  • Sickle Cell Anemia: A mutation in the beta-globin gene affects red blood cell shape and oxygen transport, leading to various complications.
• 💡 Importance: Pleiotropy explains how a single gene mutation can have a wide range of seemingly unrelated effects on an organism.

🧪 Practice Quiz

1. Which of the following is the BEST definition of pleiotropy?
   1. A) Multiple genes influencing a single trait.
   2. B) A single gene influencing multiple traits.
   3. C) Genes located on the same chromosome being inherited together.
   4. D) The interaction between alleles at different loci.
2. Cystic fibrosis is a classic example of pleiotropy. Which organ systems are MOST affected by the mutated CFTR gene?
   1. A) Liver and kidneys.
   2. B) Brain and spinal cord.
   3. C) Lungs, pancreas, and sweat glands.
   4. D) Heart and blood vessels.
3. Phenylketonuria (PKU) results from a defect in the enzyme phenylalanine hydroxylase. What are the MOST prominent effects of PKU?
   1. A) Increased bone density and muscle mass.
   2. B) Brain development issues and altered skin pigmentation.
   3. C) Enhanced cardiovascular function and improved eyesight.
   4. D) Resistance to bacterial infections.
4. Sickle cell anemia is caused by a mutation in the beta-globin gene. What is the PRIMARY consequence of this mutation?
   1. A) Increased red blood cell production.
   2. B) Altered red blood cell shape and reduced oxygen transport.
   3. C) Enhanced immune response.
   4. D) Improved blood clotting ability.
5. Why does pleiotropy occur?
   1. A) Because genes always work in isolation.
   2. B) Because gene products are involved in only one cellular pathway.
   3. C) Because the gene product participates in multiple biochemical pathways or affects multiple cell types.
   4. D) Because of random mutations with no specific effect.
6. A gene mutation causes an individual to have both weakened bones and impaired hearing. This is MOST likely an example of:
   1. A) Epistasis.
   2. B) Polygenic inheritance.
   3. C) Pleiotropy.
   4. D) Incomplete dominance.
7. Which of the following is NOT typically associated with pleiotropic effects?
   1. A) A single gene influencing seemingly unrelated traits.
   2. B) Involvement of a gene product in multiple metabolic pathways.
   3. C) A complex interaction of multiple genes for one trait.
   4. D) A mutation in a gene affecting multiple organ systems.