WBBSE Solutions For Class 10 Life Science And Environment Chapter 3 Sex Determination Of Human

Chapter 3 Sex Determination Of Human Summary

The male contains 44 autosomes and two sex chromosomes—X and Y in humans (44A+XY), so two types of gametes are formed during sperm formation through meiosis, Y containing (22A+Y) and X containing (22A+X).

Females contain 44 autosomes and two X chromosomes. So, the female can produce only one type of female gamete (22A+X) through meiosis.

Males are called heterogametic as they produce two types of gametes and females are called homogametic as they produce only one type of gamete.

Embryo produced by the fusion of the Y chromosome containing sperm and female gamete develops into a male. On the other hand, an embryo produced by the fusion of an X chromosome containing sperm and a female gamete develops into a male.

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Chapter 3 Sex Determination Of Human Long Answer Type Questions

Question 1. Describe the method of sex determination in humans.

Answer :

Sex determination in human

Sex determination in humans is controlled in two ways—primary sex determination and secondary sex determination.

1. Primary sex determination:

A normal human somatic cell carries 22 pairs of autosomes and 1 pair of sex chromosomes or allosomes. Autosomes control bodily features and sex chromosomes play a major role in sex determination.

The human female carries 22 pairs of autosomes and a pair of X chromosomes or the sex-determining chromosomes. Their chromosomal distribution can be represented as 44A+XX.

Human male, on the other hand, has one X and a Y chromosome as the sex-determining chromosomes along with 22 pairs of autosomes. In the case of males, the chromosomal set of a somatic cell is denoted as 44A+XY.

Meiotic cell division during gamete formation divides the chromosomes into two equal halves In the case of females, all gametes (ova) have identical chromosomal distribution, i.e., (22A+X) In males, two types of gametes are formed, the X-carrying gymnosperm (22A+X) and the Y-carrying androsperm (22A+Y).

When an androsperm (22A+Y) fertilizes an ovum (22A+X), a zygote is formed, which develops to form a male baby. On the other hand, the union of a gynosperm (22A+X) and an ovum results into the formation of a female baby. Therefore, the father of a child determines his or her sex.

2. Secondary sex determination:

After primary sex determination by sex chromosomes, male an female sex hormones play an important role in the development of respective gonads and the expression of the secondary sex characters.

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Chapter 3 Sex Determination Of Human Short Answer Type Questions

Question 1. Why are human females called homogametic?
Answer :

Human females called homogametic:

The chromosomal distribution of human females is 44A+XX. It means the somatic cell of a human female carries 22 pairs of autosomes and a pair of X chromosomes.

After meiosis, every ovum gets 22 autosomes and an X chromosome (22A+X). With respect to chromosomal type, a normal human female can produce identical gametes and is therefore called homogametic.

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Question 2. Why human males are called heterogametic?
Answer :

Human males are called heterogametic:

The chromosomal distribution of human males is 44A+XY. It means the somatic cell of a human male carries 22 pairs of autosomes and two different sex chromosomes, X and Y. After meiosis of the male germ mother cell, two different types of male gametes or sperms are formed.

Half of the sperms get 22 autosomes and an X chromosome (22A+X) and the remaining half get 22 autosomes and a Y chromosome (22A+Y). With respect to chromosomal type, a normal human male can produce two different types of gametes and is therefore called heterogametic.

Question 3. Mention the role of a mother in the sex determination of a human baby.
Answer :

The role of a mother in the sex determination of a human baby:

The human female is homogametic. All ova carry X chromosomes, so the mother plays no role in the sex determination of a human baby.

Question 4. What are sex-linked genes? Mention the types.
Answer :

Sex-linked genes:

Genes, present on either X or Y chromosomes, are known as sex-linked genes.

Types:

The genes present on the X chromosome are called X-linked and those present on the Y chromosome are called Y-linked genes.

Question 5. Mention the role of a father in the sex determination of a human baby.
Answer :

The role of a father in the sex determination of a human baby:

The human male is heterogametic. He has two types of sperms, endosperm (carrying the Y chromosome) and gymnosperm (carrying X chromosome).

The union of ovum and andosperm produces a male baby but the union of ovum with gymnosperm produces a female baby. Therefore, only the father plays a role in the sex determination of a human baby.

Question 6. What is the TDF gene?
Answer :

TDF gene:

In the case of male of human, there is a gene called testes determining factor in Y chromosome. Its alternative name is SRY and it helps in male child formation.

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Question 7. Why 22A+Y sperm is called androsperm and 22A+X is called gymnosperm?
Answer :

When 22A+Y sperm fuse with female gametes the embryo thereby formed, develop into a male child. So it is called endosperm as ‘andro’ means male.

On the other hand, if a 22A+X sperm fuse with female gametes the embryo thereby formed develop into a female child. So it is called gynosperm as ‘gyno’ means female.

Question 8. With the help of a cross show how the sex of the offspring of humans is determined. Similar Question: In many families, mothers are labeled as responsible for the birth of their daughter’s child. Demonstrate with the help of a cross, that this belief is not justified. Similar Question: Show with the help of a cross, who is more important among parents in determining the sex of their offspring.
Answer :

Differentiate between autosome and allosome.

Chapter 3 Sex Determination Of Human MCQs

Question 1. What would be the probability of having a boy and a girl child from a marriage between a male and a female?

1. 2:1
2. 3:2
3. 1:1
4. 1:2

Answer: 3.  1:1

Question 2. Which of the following chromosomal sets is applicable for a normal human male?

1. 44A + XX
2. 44A + XY
3. 44A + XXY
4. 44A + XYY

Answer: 2.  44A + XY

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Question 3. The chromosomal setup of a normal human female is—

1. 44A + XX
2. 44A + XY
3. 22A + X
4. 22A + Y

Answer: 1. 44A + XX

Question 4. The number of chromosomes in a normal human somatic cell is—

1. 44
2. 23
3. 22
4. 46

Answer: 4. 46

Question 5. The number of autosomes in a normal human somatic cell is—

1. 44
2. 1
3. 2
4. 46

Answer: 1. 44

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Question 6. The number of autosomes in a normal human germ cell is—

1. 44
2. 22
3. 23
4. 46

Answer: 2.  22

Question 7. The sex chromosome present in the human male gamete is—

1.  X or Y
2. Only X
3. Only Y
4. X and Y

Answer: 1. X or Y

Question 8. Number of sex chromosomes present in a normal human somatic cell is—

1. 46
2. 1
3. 44
4. 2

Answer: 4. 2

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Question 9. The number of chromosomes in the germ mother cell of a human is—

1. 46
2. 23
3. 44
4. 22

Answer: 1. 46

Question 10. Determination of sex by the qualitative character of chromosomes is known as—

1. Primary sex determination
2. Secondary sex determination
3. Both 1 and 2
4. Tertiary sex determination

Answer: 1. Primary sex determination

Question 11. Which of the following does not denote a human sperm?

1. 22A+X
2. 22A+Y
3. n
4. 44A+XY

Answer: 4. 44A+XY

Question 12. Which of the following denotes endosperm?

22A+X
22A+Y
22A+Z
None of the above

Answer: 2. 22A+Y

Question 13. Which of the following gametes obtained from males is responsible for a girl child?

1. 22A+Y
2. 22A+X
3. 44A+Y
4. 44A+X

Answer: 2. 22A+X

Question 14. A man has three girl children, the chance percentage of the fourth child being a girl is—

25%
50%
75%
100%

Answer: 2.  50%

Chapter 3 Sex Determination Of Human Answer In A Single Word Or Sentence

Question 1. A male gamete carries 22A+Y chromosomes. What will be the sex of the progeny obtained after its fertilization?
Answer: If a male gamete carries 22A+Y chromosomes, the progeny will be male after its fertilization.

Question 2. What are holandric genes?
Answer: The genes, that are present on the Y chromosome, especially in mammals, are called holandric genes. The gene responsible for hairy pinna is an example of the holandric gene.

Question 3. Give an example of a Y-linked character.
Answer: Hairy pinna in human males is an example of a Y-linked character.

Question 4. What is sex determination?
Answer: The mechanism of determining the sex of an organism is known as sex determination.

Question 5. What is the name of the Y chromosome carrying sperm?
Answer: The y chromosome carrying sperm is known as an endosperm.

Question 6. What is the name of the X chromosome carrying sperm?
Answer: The x chromosome carrying sperm is known as the gymnosperm.

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Question 7. What will be the sex of a human baby if the X chromosome carrying sperm of the father unites with the ovum of the mother?
Answer: By the union of an X chromosome carrying the sperm of a father and the ovum of the mother, a female baby will be born.

Question 8. Which sperm of the father is responsible for the birth of a girl child?
Answer: An X chromosome carrying the gymnosperm of the father is responsible for the birth of a girl child.

 

Chapter 3 Sex Determination Of Human Fill In The Blanks

Question 1. The other name of the sex chromosome is ______
Answer: Allosome

Question 2. Considering the type of gamete production, ______ males are in nature.
Answer: Heterogametic

Question 3. Considering the type of gamete production, ______ females are in nature.
Answer: Homogametic

Question 4. Y chromosome is also known as ______
Answer: Androsome

Question 5. SRY is located ______ on a chromosome.
Answer: Y

 

Chapter 3 Sex Determination Of Human State True Or False

Question 1. Human sex chromosomes are of two types.
Answer: True

Question 2. Human germ cells carry 22 autosomes.
Answer: True

Question 3. The chromosomal distribution in a human female germ mother cell is 44A+XX.
Answer: True

Question 4. The chromosomal distribution of andros¬perm is 22A+Y.
Answer: True

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Question 5. The chromosomal distribution of gynosperm is 44A+X.
Answer: False

Question 6. Both human males and females are heterogametic in nature.
Answer: False

Question 7. If a human male gamete has 22A+Y chromosomes, after fertilization, it will produce a male offspring.
Answer: True

Question 8. A pair of sex-determining sex chromosomes are present in the ovum of humans.
Answer: False

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Chapter 3 Sex Determination Of Human Match The Columns

1.

Answer: 1. A, 2. F, 3. B, 4. E, 5. D, 6. C

Chapter 3 Sex Determination Of Human Find The Odd One Out

Question 1. Sex determination, Y chromosome, Sperm,
Answer: Autosome

Question 2. Female, Homogametic, 44A+XX, Heterogametic
Answer: Heterogametic

Question 3. Sperm, Y chromosome, Male, Female
Answer: Female

Question 4. 22A+X, 22A+Y, 44A+XY, 23A+X
Answer: 23A+X

Question 5.44A+XY, 44A+XX, Heterogamete, Male
Answer: 44A+XX

Chapter 3 Sex Determination Of Human Fill In The Blanks By Looking At The First Pair

Question 1. 46 chromosomes: Somatic Cell:: 23 chromosomes: ______
Answer: Gamete

Question 2. Daughter: 44A+XX :: Son: ______
Answer: 44A+XY

Question 3. 22A+Y: Androsperm :: 22A+X: ______
Answer: Gynosperm

Question 4. Human Autosome: 44:: Human chromosome: ______
Answer: 2

Question 5. 44A+XY : Heterogametic male :: 44A+XX : ______
Answer: Homogametic female

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Chapter 3 Sex Determination Of Human Among The Four Concepts Given Three Of Them Belong To One Find That

Question 1. The x chromosome, Y chromosome, Allosome, Sex determination
Answer: Sex determination

Question 2. Egg, 22A+X, Female, Homogametic
Answer: Female

Question 3. Male, Sperm, 22A+Y, Heterogametic sex
Answer: Male