Male-Female determining chromosome:
Every living being has a definite number of chromosomes. In human beings there are 23 pairs of chromosome. Among them 22. pairs are similar in both male and female, these are Autosomes, AA. Members of the remaining pair of chromosome are different in male and female. This pair of chromosome determines the sex of human beings. As they determine the sex, so they are called X and y sex chromosome or sex determining chromosome. One of the sex chromosomes is X chromosome and the other is Y chromosome. If the sex chromosome pair is XY, the child will be male (son), and if it is XX, the child will be female (daughter). In Drosophylla (a fly) also XX indicate female andXY male. So in case of determining the sex, the role of X and Y chromosome is vital.
Now we will discuss whether the father or mother is responsible for the birth of a son or daughter. Both male and female have 44 autosomes, A and a pair of sex chromosome. Sex chromosome of a female is XX and that of the male is XY. The male gamete (sperm) bears X and Y chromosome. But the female gamete (egg) bears X and X. If the X bearing egg of the female is united (fertilize) with Y bearing sperm of the male, the child will have XY. A child having such chromosomes will be a male child. It is seen that if there is no Y chromosome, the child will never be a son. There is no Y chromosome in a female; Y chromosome is present only in male. So if a couple do not have any male child, the husband is responsible not the wife. A figure on this issue
The role of sex chromosome in determining sex of the child (i.e. whether the child will be a son or a daughter) is known to you. Now work with this grid. Write which child will be a son and which one a daughter.