How many linkage groups are present in Drosophila?

Linkage with increasing age becomes ......

There are three genes $a, b,$ and $c$. The recombination frequency between $a$ and $b$ is $20\%$,between $b$ and $c$ is $28\%$,and between $a$ and $c$ is $8\%$. What is the possible arrangement of these genes on the chromosome?

Drosophila melanogaster has $8$ chromosomes in its somatic cell. How many linkage groups will it have?

Describe linkage and recombination in detail.

When closely placed genes on the same chromosome are inherited together,the phenomenon is known as: