Chapter 4, Problem 1P

Summary Introduction

To examine:  Whether the statement “Human females have 23 different chromosomes, whereas human males have 24” is true or false.

Concept introduction: Chromosomes are condensed DNA which are visible at the time of cell division. The chromosomes are highly condensed and compacted structure consisting of the DNA held together by the histone proteins. Chromosomes are found in the higher eukaryotic organisms and their number varies between species to species. The chromosomes are diploid, 2n in somatic cells and haploid, n in the reproductive cells.

Answer to Problem 1P

Correct answer: The statement is true.

Explanation of Solution

The human beings have 23 pairs, that is, 46 chromosomes in their somatic cells. In the gametes, that is, the reproductive cells have only 23 chromosomes. These gametes fuse to form the zygote which develops into the embryo. The embryo will have 23 pairs of 46 chromosomes, one set of 23 chromosomes is inherited from the father and the other set of 23 chromosomes is inherited from the mother. Of the 23 pairs, 22 pairs are somatic chromosomes and one pair is sex chromosome. The somatic chromosomes are also called as homologous chromosomes. The sex chromosomes are homologous, XX in the females and non homologous, XY in the males. The sex chromosomes are exclusive that is they determine the sex of the individual. The structure and size of the chromosomes are different from each other. Comparing the chromosomes of human females and males based on the size and structure, it can be said that females have 23 different chromosomes and males have 24 different chromosomes. During spermatogenesis, the sperm will have either X or Y.

Hence, the statement is true.