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

Select the incorrect statement(s) from the options given below with respect to dihybrid cross.

$I.$ Tightly linked genes on the same chromosome show higher recombinations.

$II.$ Genes far apart on the same chromosome show very few recombinations.

$III.$ Genes loosely linked on the same chromosome show similar recombinations.

The frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes was explained by

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:

Linkage in Drosophila was first discovered by