Chapter 11.2, Problem 2NV

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 conditions.

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 that are involved in the determination of sex in a sexually reproducing organism. These are usually present in a single pair (2 chromosomes 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: 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 multiple genes, the phenotype or the performance of polygenic traits are continuous and discrete phenotypes are absent.