Question

Explain what determine the sex of the baby

Answer 1

In a humans, there are 46 chromosomes in pairs, i.e., 23 pairs; out of which 1 pair is sex chromosomes. In males, the sex chromosomes are X and Y, while in females, the sex chromosomes are X and X. The male gamete (n), i.e.,sperms contains 1 pair of sex chromosome, i.e., X and Y chromosomes (a sperm can be X or Y), it fuses with the female gamete (n), i.e., the ovum in the Fallopian tube. The ovum contains the chromosomes, X and X.
If during fertilisation, the X chromosome - sperm reaches first and fuses with the ovum, then, the resulting zygote (2n) would contain X and X chromosomes, then, the baby formed would be a female. But, if the Y chromosome - sperm fertilises the ovum first, then, the zygote would contain, X and Y chromosome. So, the baby would be a male. 
Therefore, the male determines the sex of the baby.