Question

A pleiotropic gene
A. Controls multiple traits in an individual
B. Is expressed only in primitive plants
C. Is a gene evolved during Pliocene
D. Controls a trait only in combination with another gene

Answer 1

A gene is defined as the unit of DNA responsible for the appearance of inheritance of characters. Genes are present on the long DNA molecules called chromosomes. Thus, genes are the units of inheritance.

Complete answer: Pleiotropy is defined as the ability of a gene to have a multiple phenotypic effect as it influences a number of characters simultaneously. The gene having the ability to control expression of a number of characters and have multiple phenotypic effects is called pleiotropic gene.
For example- in Drosophila, the gene for wing size also affects the nature of balancers, eye color, fertility, longevity, etc.
In pea seeds, the genes for starch synthesis produce more than one effect. It has two alleles B and b, when a gene produces more than one phenotype then we choose the particular phenotype to examine.
It is not important that all the traits are equally influenced. The effect is more evident in one case whereas less evident in the case of others.
In pea, the gene which determines the flower color also controls the color of the seed coat and presence of red spots in the leaf axils.
In the human being Marfan's syndrome, sickle cell anemia, phenylketonuria, alkaptonuria, etc. are exhibited by the pleiotropic gene.
So the correct answer is “Option A” **that a pleiotropic gene controls multiple traits in an individual.

Note: **So, it can be inferred from the concept of pleiotropic genes that genes code for a protein that has either a cascade like signaling function or is used by various cells. Also most of the genes have multiple effects and are pleiotropic.