Question

The phenomenon of pleiotropism refers to

• A. Presence of two alleles, each of the two genes controlling a single trait
• B. A single gene affecting multiple phenotypic expression
• C. More than two genes affecting a single character
• D. Presence of several alleles of a single gene controlling a single crossover

Answer 1

The Correct Option is B

Pleiotropism is a genetic phenomenon where a single gene influences multiple phenotypic traits. This means that a mutation in a pleiotropic gene can have widespread effects on an organism's phenotype. Understanding pleiotropism is crucial in genetics as it explains why changes in a single gene can lead to various observable effects.

From the given options, let's analyze: 

Presence of two alleles, each of the two genes controlling a single trait

This describes an example of simple Mendelian inheritance involving two separate genes, not pleiotropy.

A single gene affecting multiple phenotypic expression

This correctly describes pleiotropism, as it indicates one gene impacts multiple traits.

More than two genes affecting a single character

This is describing polygenic inheritance, where multiple genes influence a single trait.

Presence of several alleles of a single gene controlling a single crossover

This scenario is not directly related to pleiotropy; rather it refers to allele variation and genetic recombination.

Therefore, the correct answer is: A single gene affecting multiple phenotypic expression.

Answer 2

In pleiotropy, a single gene has multiple effects on the phenotype, leading to the expression of multiple traits or characteristics. These different traits may seemingly be unrelated to each other, and they arise from the influence of the same gene on various biochemical pathways or developmental processes within the organism. Pleiotropy is a common occurrence in genetics and can result in diverse phenotypic effects caused by alterations in a single gene.

Therefore, The correct option is (B): A single gene affecting multiple phenotypic expression