Chapter 26, Problem 1RQ

Match each of the following items with all the terms it applies to:

Summary Introduction

To match: Each item with the applicable terms.

Answer to Problem 1RQ

Correct answer:

(a) X or Y	3. sperm and ova, 4. sex chromosomes, 5. germ cells
(b) Inactivated X chromosome	8. Barr body
(c) XX	2. fertilized egg, 7. female chromosomes
(d) XY	2. fertilized egg, 6. male chromosomes
(e) XX or XY	2. fertilized egg
(f) Autosomes	1. chromosomes other than sex chromosomes

Explanation of Solution

1. (a) X or Y – 3. sperm and ova, 4. sex chromosomes, 5. germ cells

   The cells which contain half the number of chromosomes are known as germ cells. Sperm and ova are germ cells produced by males and females, respectively. Each germ cell has 23 chromosomes, 22 autosomes, and 1 sex chromosome. Male germ cells (sperms) can have either X or Y chromosome, whereas female germ cells (ova) will always have an X chromosome.

2. (b) Inactivated X chromosome – 8. Barr body

   Female sex chromosomes have genotype XX. One X out of these is condensed and inactive. It appears to be a small and dense stained structure present in the nuclei of the cells. This inactive and condensed X chromosome is known as a Barr body. Barr bodies are absent in males.

3. (c) XX - 2. fertilized egg, 7. female chromosomes

   Half of the male germ cells contain an X chromosome, and the other half has Y chromosome. If male germ cell carrying X chromosome fuses with the female germ cell, then the fertilized egg would have XX chromosomes. Presence of XX chromosomes indicates that the fetus is female.

4. (d) XY - 2. fertilized egg, 6. male chromosomes

   X and Y chromosomes are sex chromosomes present in humans. The fusion of male germ cell containing Y chromosome and female germ cell would result in the production of zygote with genotype XY.

5. (e) XX or XY – 2. fertilized egg

   In humans, male and female germ cells have 1 sex chromosome each. About 50% of male germ cells have X chromosome whereas the other 50% has Y chromosome. All the female germ cells have X chromosome in them. The fusion of male and female germ cells inside the female body is known as fertilization. The zygote formed after fertilization has double chromosomes as compared to the germ cells. This zygote or fertilized egg will have genotype XX in case of females and XY in case of males.

6. (f) Autosomes – 1.chromosomes other than sex chromosomes

   Every human being has 46 chromosomes that is 23 pairs of chromosomes. Out of these 23 pairs, 22 are autosomes, and 1 pair of the chromosome is sex chromosome. Autosomes are responsible for various features of the human body such as eye color, height, hair color, and many more.