Question 1 What are sex chromosomes?
Question 2 Which of the two sperm or egg decides the sex of the child?
Question 3 Which of the two combination of sex chromosomes produces boy :XX or XY?
Question 4 Which of the two combination of sex chromosomes produces girl :XX or XY?
Question 5 Who is responsible for the sex of unborn baby :Father or mother. How?
Question 6 Name 2 sex chromosomes?
Question 7 Explain how sex is determined in the unborn baby?
Sex Chromosomes
chromosomes are present inside the nucleus of every cell of the human body. All the human beings have 23 pairs of chromosomes in the nuclei of their normal body cells. Out of these 23 pairs of chromosomes, one pair of chromosome are called sex chromosome.
The two chromosomes that determine the sex of an offspring or baby are called sex chromosomes. The two sex chromosomes are named X chromosomes and Y chromosomes.
The gamete are special cells called reproductive cells. The gametes contain only 23 single chromosomes and hence they have only one of the two sex chromosomes that exist in the normal body cells. In females all the gametes or all the egg cells contain X chromosomes.
In males, half of gametes or sperms have X chromosomes and half of gametes or sperm have Y chromosomes.
The baby developed from XX chromosome of sex chromosome in zygote is a girl. And the baby developed from XY combination of sex chromosomes in zygote will be a boy.
Determination of sex of a Baby
The sex of a baby to be born is decided at the moment the egg cell of woman gets fertilised by the sperm of man and pregnancy occurs.
The instructions for determining the sex of baby are present in the sex chromosomes which are in the nucleus of the fertilised egg called zygote.
(1) If a sperm carrying X chromosome fertilises an egg cell which carries X chromosomes, then the zygote formed will have XX combination of sex chromosomes due to which the child born will be a girl.
(2) If a sperm carrying Y chromosomes fertilises an egg cell which carries X chromosomes, then the zygote formed will have XY combination of sex chromosomes due to which the child born will be a boy.
The sex of unborn child depends on whether the zygote formed at the time of fertilisation has XX combination of sex chromosomes or XY combination of sex chromosomes.
It is the sperm of man that determines the sex of the child. This is because half of the sperms have X chromosomes and other half have Y chromosomes.
The egg cells or ova of woman cannot decide the sex of the child because all the egg cells contain the same sex chromosomes, X chromosomes.
(1) If the father contributes X sex chromosomes at fertilisation through its sperm, the baby born will be a girl.
(2) If the father contributes Y sex chromosomes at fertilisation through its sperm, the baby born will be a boy.
Father is responsible for the sex of the baby which is born.
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