How is sex determined in human beings?
Human beings exhibit male heterogamy. In humans, males $(XY)$ produce two different types of gametes, $X$ and $Y$. The human female $(XX)$ produces only one type of gametes containing $\mathrm{X}$ chromosomes. The sex of the baby is determined by the type of male gamete that fuses with the female gamete. If the fertilizing sperm contains $\mathrm{X}$ chromosome, then the baby produced will be a girl and if the fertilizing sperm contains $Y$ chromosome, then the baby produced will be a boy. Hence, it is a matter of chance that determines the sex of a baby. There is an equal probability of the fertilizing sperm being an $\mathrm{X}$ or $\mathrm{Y}$ chromosome. Thus, it is the genetic makeup of the sperm that determines the sex of the baby. (figure)
$A$ : $XO$ type sex determination is found in large number of insects.
$R$ : Some of the sperms bear the $X-$chromosome whereas some do not
Match the items of column $I$ with column $II$
Column $I$ | Column $II$ |
$(a)\; XX-XO$ method of sex determination | $(i)$ Turner's syndrome |
$(b)\; XX-XY$ method of sex determination | $(ii)$ Female heterogametic |
$(c)$ Karyotype$-45 $ | $(iii)$ Grasshopper |
$(d)\; ZW-ZZ$ method of sex determination | $(iv)$ Female homogametic |
Select the correct option from the following
In our society a woman is often blamed for not bearing male child. Do you think it is right ? Justify.
While solving the problem of sex determination in large number of insects, it was observed that
Assertion : In humans, the gamete contributed by the male determines whether the child produced will be male or female.
Reason : Sex in humans is a polygenic trait depending upon a cumulative effect of some genes on $X-$ chromosome and some on $Y-$ chromosome.