Chapter 10, Problem 27A

Summary Introduction

To explain:

The three processes that increase genetic variation

Introduction:

The main advantage of sexual reproduction is that it produces genetic variation in species. Genetic variation arises due to differences in genetic sequence in DNA among individuals. Genetic variation helps species survive better in adverse conditions. Meiosis contributes to the amount of genetic recombination in a particular species.

Answer to Problem 27A

Genetic variation can be increased by the following processes:

1. Crossing over
2. Random mating
3. Independent assortment

Explanation of Solution

Genetic variation is possible during crossing over and fertilization when gametes randomly combine.

1. Crossing over- During crossing over chromosomal segments are exchanged between a pair of homologous chromosomes. This results in exchange of genes between homologous chromosomes. Crossing over produces new combination of genes. This new combination of genes is called genetic recombination.
2. Random mating- Random mating allows organisms to combine their gametes and chromosomes randomly. Organisms select their mates randomly and this leads to random fertilization of gametes. This creates genetic variation.
3. Independent assortment- Independent assortment of genes also contributes to genetic recombination. Genes that are linked together on the same chromosomes usually travel together in a gamete. The crossing over of linked genes is a source of genetic variation.