$A$ child who inherits an $X-$chromosome from her father will be a boy.

Exchange of genetic material takes place in

$(a)$ Explain,giving examples,how artificial selection has helped in the formation of newer varieties of cauliflower.
$(b)$ List the steps involved in the formation of new species.
$(c)$ How do different races of human beings belong to the same species?

What are the differences that arise among organisms of the same species called?

Two pea plants,one with round green seeds $(RRyy)$ and another with wrinkled yellow $(rrYY)$ seeds,produce $F_1$ progeny that have round,yellow $(RrYy)$ seeds. When $F_1$ plants are selfed,the $F_2$ progeny will have new combinations of characters. Choose the new combinations from the following:
$(i)$ Round,yellow
$(ii)$ Round,green
$(iii)$ Wrinkled,yellow
$(iv)$ Wrinkled,green

$A$ trait may be inherited, but may not be expressed. Justify this statement with the help of a suitable example.