Chapter 10, Problem 17STP

Summary Introduction

To describe:

Occurrences during fertilization in in the animal with given number of chromosomes.

Introduction:

Meiosis is a type of cell division that reduces the number of chromosomes; therefore it is referred to as a reduction division. It occurs in reproductive cells resulting in formation of gametes which fuse together during fertilization. Meiosis involves two consecutive cell divisions called meiosis I and meiosis II.

Answer to Problem 17STP

The given animal has six chromosomes in the sex cells. After fertilization the zygote will be a diploid with six pairs of chromosomes.

Explanation of Solution

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 one haploid gamete fuses with another haploid gamete, the process is called fertilization. A cell with n number of chromosomes is called a haploid cell. The result of fertilization is a diploid cell with 2n number of chromosomes; n chromosomes from male parent plus n chromosomes from female parent.

The given diagram shows that there are six chromosomes in the sex cells (gamete) of the animal.

Now when this gamete undergoes fertilization by fusing with another gamete, it will produce a zygote which will have six pairs of chromosomes. The gametes have half the number of chromosomes. The zygote will have 2n number of chromosomes. So here, it will have 12 chromosomes or six pairs of chromosomes. It will be a diploid cell.