If $F_2$ of a dihybrid cross contains only parental combinations,then Mendel would have discovered .....

Linked genes are present on

Genes $A, B$,and $C$ are linked. Genes $A$ and $B$ are closer than $A$ and $C$. Find out the correct option for the given statements:
$I.$ $A$ might be before $B$ and $C$
$II.$ $B$ might be between $A$ and $C$
$III.$ $C$ might be between $A$ and $B$
$IV.$ More crossovers have occurred between $A$ and $C$ than $A$ and $B$.

Primary source of allelic variation is

Which of the following was $NOT$ included in Mendel's laws?

The following experiment is the result of a dihybrid cross performed by Morgan. Identify the proportions of $P, Q, R,$ and $S$.