Determination of Sex


Reaching The Age of Adolescence II - Concepts
Class - 8th Foundation NTSE Subjects
 
 
Concept Explanation
 

Determination of Sex

Determination of Sex of the Child

Human beings have 46 chromosomes in the nuclei of their cells. Of these, 44 are known as autosomes and the last pair is termed the sex chromosomes. This last pair is different in males and females. In males, it is XY and in females it is XX. The gametes (ovum and sperm) have half the number of chromosomes as that of cells occurring elsewhere in the body. This means that an egg will always have 22 + X chromosomes while a sperm will have either 22 + X or 22 + Y chromosomes.

During fertilization, if an egg fuses with a 22 + Y sperm, the resultant zygote will develop into a male child and if an egg fuses with a 22 + X sperm, the resultant zygote will develop into a female child. After understanding this, can you now analyze, which of the two, the father or the mother is responsible for determining the sex of the child.

Sex Determination - Boy or Girl :

What determine whether the baby developing inside the mothers womb is a boy or a girl? This is determined by a thread like structure called chromosomes. Chromosomes, located inside the nucleus of zygote or fertilized egg, carry heredity information in the form of genes. The chromosomes which carry genes for sex determination are called sex chromosomes. Human beings have 22 pairs of autosomes (chromosomes other than sex chromosomes) and one pair  of sex chromosome. Chromosomes determine everything from hair colour and eye colour to sex. Whether you are a male or female depends on the presence or absence of certain chromosomes. There are two types of sex chromosomes- X and Y. Female cell contains two X chromosomes (XX) while male cells carry one X one and one Y chromosomes (XY).

  • If the sperm carrying X chromosomes fertilizes the egg, it would be a girl, since the chromosome pair will be XX
  • If the sperm carrying Y chromosome fertilizes the egg, the baby will be a boy, since the chromosome pattern will be XY.
  • Therefore, it is the Y chromosome that is essential for the development of the male reproductive organs, and with on Y chromosome, an embryo will develop into a female.

    Sample Questions
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    Question : 1

    How many pairs of chromosomes are present in human beings?

    Right Option : C
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    Explanation
    Question : 2

    Sex determination is done with the help of ___________________

    Right Option : A
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    Explanation
    Question : 3

    Sex chromosomes in males are ___________________.

    Right Option : D
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    Explanation
     
     


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