Genetic map is one that

The percentage of crossing over will be more if

The distance between two genes in a chromosome is measured in cross-over units which represent

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 $B$

Frequency of recombination between gene pairs on same chromosome as a measure of the distance between genes to map their position on chromosome, was used for the first time by