Chapter 10.1, Problem 7MI

Summary Introduction

To analyze:

The phase of meiosis when crossing over takes place.

Introduction:

Reproductive cells which pass on genetic traits from the parent to child are produced by the process of meiosis. In order to maintain the same number of chromosomes in each generation, an organism produces gametes. Gametes are sex cells and have half the number of chromosomes.

When gametes combine in fertilization, the number of chromosomes is restored.

Answer to Problem 7MI

Crossing over occurs during prophase I of meiosis. It results in genetic variations.

Explanation of Solution

During prophase I, the replicated chromosomes appear as two sister chromatids. The homologous chromosomes condense and begin to form pairs in a process called synapsis. The homologous chromosomes are held tightly together along their lengths. Some segments of homologous chromosomes get exchanged during synapsis. This process is called crossing over. It is a process during which chromosomal segments are exchanged between a pair of homologous chromosomes. This results in an exchange of genes between homologous chromosomes.