What will be the probability of next child to be a girl from parents who have 5 daughters?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 50%
In humans, the sex of the child is decided by the sperm. All ova carry an X chromosome. Half of the sperms carry X and the other half carry Y.
Ovum (X) + sperm (X) → XX, a girl
Ovum (X) + sperm (Y) → XY, a boy
So each pregnancy has a 50 per cent chance of a girl and a 50 per cent chance of a boy. Every birth is a separate event. The five daughters born earlier do not change the chance for the next child.
NCERT Extract:
Sex Determination in Humans – “… In case the ovum fertilises with a sperm carrying X-chromosome the zygote develops into a female (XX) and the fertilisation of ovum with Y-chromosome carrying sperm results into a male offspring. Thus, it is evident that it is the genetic makeup of the sperm that determines the sex of the child. It is also evident that in each pregnancy there is always 50 per cent probability of either a male or a female child.”