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

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

The frequency of recombination will be higher if.....

In female $Drosophila$,linked genes show recombination during meiosis. However,such recombination does not occur during sperm formation in male $Drosophila$. Why?

The recombination frequency between the genes $a$ and $c$ is $5\%$,$b$ and $c$ is $15\%$,$b$ and $d$ is $9\%$,$a$ and $b$ is $20\%$,$c$ and $d$ is $24\%$,and $a$ and $d$ is $29\%$. What will be the sequence of these genes on a linear chromosome?

Describe linkage and recombination in detail.