The phenomenon of crossing over in diploid organisms is responsible for

Two dominant non-allelic genes are $50$ map units apart. The linkage present is:

Linkage groups can be separated during . . . . . . in meiosis.

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$:
Mendel's law of independent assortment does not hold good for the genes that are located closely on the same chromosome.
Reason $(R)$:
Closely located genes assort independently.
In the light of the above statements,choose the correct answer from the options given below:

Mendel studied seven pairs of traits in pea plants,which allow for $21$ possible combinations. If you are told that one of these combinations does not show independent assortment in a subsequent study,what would be your reaction?

The greater the length of the chromosomes in an organism, the greater the genetic variation. This variation is obtained from which of the following processes?