Geneticists plot the relative locations of genes on chromosomes by which of these methods?

Which of the following combinations of characters selected by Mendel shows linkage?

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:

Genes which are located on the same chromosome are

The term 'crossing over' was coined by

Select the correct statement regarding dihybrid crosses and linkage.