Genes $A, B$ and $C$ are linked. Genes $A$ and $B$ are more close 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 crosses has occurred between $A$ and $C$ than $A$ and $B$

What is recombination ? Discuss the applications of recombination from the point of view of genetic engineering.

The experiment shown in the given figure has been carried out by Morgan to show the phenomenon of linkage and recombination. If in cross $I$, genes are tightly linked and in cross $II$, genes are loosely linked then what will be the percentage of recombinants produced in cross $I$ and cross $II$ respectively?

Who used the frequency of recombination ?

Crossing over is