Summary
A single gene influences several apparently unrelated traits, as in Marfan syndrome.
In depth
One gene product used in many tissues causes several effects. Marfan syndrome (fibrillin-1 mutation) affects the skeleton, eyes and aorta; sickle cell allele affects blood, spleen and malaria resistance.
Pleiotropy complicates selection because a gene beneficial for one trait may harm another.
Pleiotropy arises because one protein is used in several places or because an early developmental step affects many later structures. Phenylketonuria affects pigment, brain development and body odour, all from lack of phenylalanine hydroxylase. Albinism genes can influence vision as well as colour.
Pleiotropy complicates evolution: an allele good for one trait may be harmful for another, which is a trade-off; it may also explain ageing by antagonistic pleiotropy, in which alleles that boost early fitness cause harm late in life.
Example: the gene for Marfan syndrome, fibrillin-1, is part of connective tissue everywhere, so tall stature, flexible joints, lens dislocation and aortic weakness all occur.
Frequently asked questions
What is Pleiotropy?
A single gene influences several apparently unrelated traits, as in Marfan syndrome.
Which area of biology covers Pleiotropy, and how advanced is it?
Pleiotropy is one of the 54 topics in Genetics. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Dominant and Recessive, Allele, Sex-Linked Inheritance.
Can you give an example of Pleiotropy?
Phenylketonuria affects intelligence and pigmentation through one enzyme deficiency.
What should I learn before Pleiotropy?
Work through the Beginner topics in Genetics first, such as Heredity, Gene, Allele, then return to Pleiotropy. Intermediate topics assume the Beginner vocabulary.
What topics are related to Pleiotropy?
The closest topics to Pleiotropy are Dominant and Recessive, Allele, Sex-Linked Inheritance, Genetic Drift. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Pleiotropy?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Pleiotropy. To practise the whole of Genetics, use the Genetics quiz.
How is Pleiotropy different from Dominant and Recessive?
Pleiotropy: A single gene influences several apparently unrelated traits, as in Marfan syndrome. Dominant and Recessive: A dominant allele shows its effect when present in one copy; a recessive allele only shows when two copies are present. Read both side by side and note what each one explains.
How should I study Pleiotropy step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Dominant and Recessive and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.