Question

In human beings, the statistical probability of getting either a male or female child is 50:50. Give a suitable explanation.

Answer 1

Probability of getting either a male or female child:

1. Humans have 23 pairs of sex chromosomes out of which 1 pair is a sex chromosome.
2. Females have identical sex chromosomes represented as 22+XX. Male non-identical sex chromosomes, one part has 22+X composition and the other part bears 22+Y.
3. The number of chromosomes is halved during gametogenesis. So 50% sperms of males have X chromosomes and the other 50% with Y chromosomes.
4. During ejaculation, more than a million sperm are ejected into the female vagina.
5. If the sperm that reaches the egg has a Y chromosome, the zygote will have a sex chromosome, XY and it will be male. If the sperm that reaches the egg has an X chromosome, the zygote will have, an XX sex chromosome,
6. Since the ratio of the X chromosome and Y chromosome in a male gamete is 50:50, the probability of male or female infants is also 50:50.
7. Therefore the statistical probability of getting either a male or female child is 50:50 since the sex-determining male sperm has a 50:50 chance of bearing an X or Y chromosome.