Chapter 11.2, Problem 7MI

Summary Introduction

To determine:

The role of epistasis, X chromosome inactivation, polygenic traits and X linked traits in inheritance.

Introduction:

Inheritance of a trait is based on the chromosomes that are acquired from the parents of the individuals. In the body there are different mechanisms such as epistasis and X chromosome inactivation by which the expression of a trait is controlled.

Explanation of Solution

Given below is the analysis of the role of different mechanism in inheritance.

	Role in inheritance	Example
Epistasis	It is a process, in which effect of a gene influences the expression of the other gene.	Albinism is a condition, which is caused by lack of production of melanin pigments in an individual. Although the gene directly affects the melanin production, but the skin color or the eye color is also affected by this conditions.
Polygenic traits	They are the traits, which are coded by different genes and a single trait represents the cumulative effect of all the genes.	For example, inheritance of eye color, skin color, height, pattern of fingerprint, etc.
X chromosome inactivation	This is the process, in one of the X chromosomes in the somatic cells of the females to ensure that there is no over expression of the X chromosomes in the body.	The patchy coat color in calico cats is an example of X chromosome inactivation in females. The coat color in the female cats are coded by X chromosomes, in case the cat is heterozygote for cat color, the random activation of X chromosome at different places in the fur gives them a patchy appearance.
X linked traits	X linked traits are caused are caused by inheriting X chromosome having the allele expressing a particular trait. The inheritance of X linked traits are different in males and females, as the male members carry a single copy of X chromosomes and females carry two. So, the diseased or traits which are X linked are generally more commonly observed in males.	Red green color blindness is a condition caused by a faulty allele on X chromosome.