Chapter 11.2, Problem 3MI

Summary Introduction

To determine:

Definition of terms incomplete dominance, codominance, multiple alleles, epistasis, sex chromosomes, autosomes, sex linked traits, and polygenic traits.

Explanation of Solution

Incomplete dominance: It is a heterozygous condition in which neither allele in a pair shows complete dominance over the other. Neither of the alleles in the pair is dominant and rather combines to display an intermediate trait by mixing of two traits.

Codominance: It is a condition, in which two alleles are equally dominant. In this condition, the resultant phenotype is the cumulative expression of both the alleles.

Multiple alleles: In general, the genes exist in two alternate forms, these alternate forms are known as alleles. A condition, in which there are more than 2 forms or alleles for a single gene is called multiple allelic condition.

Epistasis: It is an interaction between two or more genes that influences a single phenotype. In other words, it is a condition, in which the expression of a gene influences the phenotype of the other genes.

Sex chromosomes: These are the chromosomes which are involved in determination of a sex in sexually reproducing organism. These are usually present in a single pair (2 chromosome in a cell).

Autosomes: These are the chromosomes that are not involved in the sex determination of an organism. They are more in number as compared to the sex chromosome.

Sex linked traits: The traits, which are controlled by the sex of an individual and the traits that are coded by the genes present on the sex chromosomes are known as sex linked traits.

Polygenic traits:The polygenic traits are defined as the traits, which are under the influence of many genes. In this case, the cumulative effect of the many genes gives rise to a trait in the individuals. Due to the influence of the multiple genes, the phenotype or the performance of the polygenic traits are continuous and discrete phenotypes are absent.