The number of linkage groups in $E. coli$ is:

Linkage decreases the frequency of

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:

What is a linkage group?

Which of the following animals was selected by $T.H. Morgan$ for studying linkage?

$A$ genetic map is one that