Chapter 13, Problem 1IQ

1. a. How many chromosomes are there in the somatic cells of an animal in which 2n = 14? __________How many chromosomes are in its gametes? _________
2. b. If n = 14, how many chromosomes are there in diploid somatic cells? _______ How many sets of homologous chromosomes are in the gametes?
3. c. If 2n = 28, how many chromatids are there in a cell after chromosome duplication has occurred prior to cell division? ___________ What is the difference between sister chromatids and nonsister chromatids?

Summary Introduction

To determine: The number of chromosomes present in a somatic cell of an animal in which 2n=14.

Introduction: Chromosomes are long thread like structures present in all cells of the body. These chromosomes contain coded genetic materials in the form of genes and that are transmitted to the succeeding generations by the process of cell division. A diploid cell contains two set of chromosomes, whereas a single set of chromosome is present in haploid cells.

Answer to Problem 1IQ

The number of chromosomes present in the given somatic animal cell is 14.

Explanation of Solution

Somatic cells include all the body cells except the gametes (sperms and ova). Under normal conditions, all the somatic cells exist in a diploid form. It is given that the animals have (2n=14) and (2n) represents the diploid condition of the cell. It is given that the cell is somatic and hence, it is also diploid. Thus, the number of chromosomes present in the given somatic animal cell is 14.

Summary Introduction

To determine: The number of chromosomes present in the gamete cells of an animal is 2n=14.

Answer to Problem 1IQ

The number of chromosomes present in the cell’s gamete is 7.

Explanation of Solution

Gametes are the reproductive cells and include the sperms and ova. Under normal conditions, all the gametes exist in a haploid condition. It is given that 2n=14 where (2n) indicates diploid condition of the cell. Therefore, the gametes that are haploid have 7 chromosomes in its cell.

Summary Introduction

To determine: The number of chromosomes present in a diploid somatic cell is n=14.

Introduction: Somatic cells include all the body cells except the gametes. Gametes include the reproductive cells, which are the sperms and ova.

Answer to Problem 1IQ

The number of chromosomes present in a diploid somatic cell, when n=14 is 28.

Explanation of Solution

It is given that n=14 and (n) indicates the haploid condition and when the cells are diploid, the number of chromosomes is 28 (since n=14, 2n=28). Therefore, the diploid somatic cell has 28 chromosomes.

Summary Introduction

To determine: The number of set of the homologous chromosomes present in the gametes.

Answer to Problem 1IQ

The set of homologous chromosomes present in the gamete is 1.

Explanation of Solution

Homologous chromosomes are the pair of chromosomes containing one maternal and one paternal chromosome. Homologous chromosomes are paired chromosomes that are identical in length, centromere location, and the gene loci but the sequence of the gene varies. The gametes are haploid and hence, they possess only a single set of chromosomes that they contribute it during the fertilization. Therefore, the set of homologous chromosomes present in the gamete is 1.

Summary Introduction

To determine: The number of chromatids present after the occurrence of duplication of the chromosome prior to the cell division in a cell containing 2n=28.

Introduction: Chromosomes are long thread like structures present in the cell. Each chromosome constitutes two chromosomal arms that are linked together by the centromere. The coded information in the form of genes is arranged in the chromatids.

Answer to Problem 1IQ

The number of chromatids present in the cell after the duplication of chromosome had occurred prior to cell division, when 2n=28 is 56.

Explanation of Solution

If the chromosomes undergo duplication before the onset of cell division, the number of chromosomes in the cell doubles. Since each chromosome has two chromatids, the number of chromatids when 28 chromosomes are present in the cell 56.

Summary Introduction

To differentiate: Sister chromatids from non-sister chromatids.

Explanation of Solution

Criteria	Sister chromatids	Non-sister chromatids
Formation	Sister chromatids are formed when the chromosome undergoes duplication during the S phase of interphase.	Non-sister chromatids occur on different chromosomes of the homologous chromosomes.
Centromere	They are joined by the centromere at the center and all along their length by cohesive proteins.	Since they are present in different chromosomes, they are not linked by the centromere.