Question

In human beings, the statistical probability of getting either a male or a female child is 50:50. Which of the following is the cause behind it?

• A. The sex of an infant is determined by the type of sex chromosome contributed by the male gamete.
• B. The ratio of male gametes containing X chromosome and those containing Y chromosome is 50:50.
• C. Both A and B.
• D. None of these

Answer 1

The correct option is C Both A and B.

• The sex of an infant is determined by the type of sex chromosome contributed by the male gamete. A male produces two types of sperms, one type bears 22+X composition and the other, 22+Y. Therefore, a male has 50% sperms with X chromosomes and the other 50% with Y chromosomes.

Anyone of the two types of the sperms can fertilize the egg. If a Y bearing sperm fertilizes the egg, the zygote will be a male (XY) and when X bearing sperm fertilizes the egg, the resulting zygote will be female (XX). Since the ratio of the X chromosome and the Y chromosome in a male gamete is 50:50. The statistical probability of male or female infants is also 50:50.