Question

Pleiotropic gene
A. Controls only one phenotype
B. Controls several phenotypes
C. Masks the expression of another non-allelic gene
D. Inhibits cross over
E. Promotes crossing over

Answer 1

Hint: Pleiotropy is related to the genotypic and phenotypic characters of an organism.

Complete answer:
The term pleiotropy is derived from a Greek term, where pleio means “many” and tropic means “affecting”. A pleiotropic gene is such a gene that controls or regulates multiple phenotypic characters.
Sometimes genes that may be affected due to mutations or replication errors are pleiotropic. People with the disorder Marfan syndrome, usually have a set of unrelated symptoms such as unusually tall, thin digits, dislocated eye lenses, and cardiac problems. These symptoms may seem unrelated but ultimately trace back to a single gene.

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Additional Information:
Different categories of pleiotropy are as follows:
- Gene Pleiotropy - The studies involve the number of traits and biochemical factors influenced by a gene.
- Developmental Pleiotropy- Deals with mutations and their effect on multiple traits.
- Selectional Pleiotropy- Focuses on the different fitness components affected by a gene mutation.
- Antagonistic Pleiotropy- Based on the study of gene mutations that provide advantages initially but maybe disadvantageous later in life.

Some examples of the pleiotropic disorder are:
- Sickle Cell Anaemia
- Phenylketonuria or PKU
- Frizzled Feather Trait
- Marfan Syndrome

So, the correct answer is, ‘Pleiotropic genes control several phenotypes’.

Note: In pleiotropy, a single gene influences multiple phenotypic characters, but it has to be remembered that these phenotypic characters are unrelated, whereas in polygenic inheritance many genes affect a single phenotypic character.