Improvement of the human race through hereditary qualities is called:

Select the correct option for the following statements:
$P - F_1$ generation shows traits of both parents.
$Q - F_1$ generation shows a new trait (intermediate).
$R - F_1$ generation shows only one of the two parental traits.
$\quad \quad P \quad Q \quad R$

Tjio and Levan's contribution is very significant because they

Mother and father both have blood group '$A$'. They have two children,one with blood group '$O$' and the second one with blood group '$A$'. They have:

Match the following:

Column-$I$	Column-$II$
$(1)$ Inheritance of two genes	$(a)$ $ABO$ blood group
$(2)$ Incomplete dominance	$(b)$ $1:2:1$
$(3)$ Codominance	$(c)$ $9:3:3:1$
$(4)$ Inheritance of one gene	$(d)$ $3:1$

Match the following:

Column – $I$	Column – $II$
$(1)$ Failure of cytokinesis	$(p)$ To study inheritance of particular traits
$(2)$ Trisomy of $21$	$(q)$ Polyploidy
$(3)$ Error of metabolism	$(r)$ Down's syndrome
$(4)$ Pedigree analysis	$(s)$ Phenylketonuria