The arrangement of genes on chromosomes is

Given below is a highly simplified representation of the human sex chromosomes from a karyotype. The genes $a$ and $b$ could be of

How many linkage groups are present in Drosophila?

In $Drosophila$,long wing and broad abdomen characters are dominant over vestigial wing and narrow abdomen characters. $A$ pure-breeding $Drosophila$ with long wings and broad abdomen is crossed with a pure-breeding vestigial-winged and narrow-abdomened $Drosophila$. Two of the $F_1$ individuals were crossed,and the following results were produced in the $F_2$ generation: $482$ $Drosophila$ with long wings and broad abdomen,and $154$ $Drosophila$ with vestigial wings and narrow abdomen. Which one of the following is illustrated by these results?

What is recombination? Discuss the applications of recombination from the point of view of genetic engineering.

Which method can be used to determine the location of specific genes on a chromosome?