In human beings, there are 23 pairs of chromosomes. Out of these 23 pairs of chromosomes (i.e. 46…
In human beings, there are 23 pairs of chromosomes. Out of these 23 pairs of chromosomes (i.e. 46 chromosomes), 22 pairs of chromosomes are called autosomes and one pair of chromosomes. i.e. two chromosomes are called sex chromosomes. The sex chromosomes are of two types – 'X' chromosomes and 'Y' chromosomes. The sex of a child (i.e. progeny), is decided at the time of fertilisation. In other words, at the time of zygote formation the sex chromosomes inherited from the parents of a child decide whether the new born will be a boy or a girl.
(a) What are chromosomes ?
(b) Why is the pair of sex chromosomes in human males called mismatched pair ?
(c) (A) Show with the help of a flow chart that the statistical probability of getting a boy or a girl is 50 : 50.
Solution
(a) Chromosomes carry genes which control the traits of an organism./Chromosomes contain information for inheritance of features from parents to next generation in form of DNA (deoxyribonucleic acid) molecules
(b) Men have one normal sized X chromosome while Y chromosome is short.
(c) (A) [Diagram: Sex determination in Human beings - Parents Father XY, Mother XX; Gametes X,Y from father and X,X from mother; Zygote formed after fusion of gametes: XX Female, XX Female, XY Male, XY Male; offspring 50% probability of a Female child, 50% probability of a male child]