Question

When a sperm bearing y chromosome fertilises with egg,then why the child born not be like his father??

Answer 1

b'coz it is a sexual reproduction and the offspring is different from his parents so that's why............

Answer 2

When an egg is fertilized by the Y chromosome from male sperm the resulting baby will be a boy. Y chromosome from male carries all the characteristics of father while X chromosome(egg) from female have all characteristics of mother. So when egg fertilized by the Y chromosome from male the resulting baby will have mix characteristics of mother and father.
This is reason in sexual reproduction the new born have new characteristics resulting from characteristics of both parents.