The tendency of genes to remain together during the process of inheritance is known as

The term “linkage” was coined by

Morgan hybridised yellow-bodied, white-eyed females to brown-bodied, red-eyed males and intercrossed their $F_{1}$ progeny. He observed that

$(a)$ $F_{2}$ ratio was deviated very significantly from the $9 : 3 : 3 : 1$ ratio

$(b)$ Both genes did not segregate independently of each other

$(c)$ Recombinant types are not obtained in $F_{2}$ generation

$(d)$ Both genes segregate independently of each other

Select the correct set of statements :

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 $B$

Crossing over in diploid organism is responsible for

In order to calculate map distance of genes on a chromosome, one must know the