Which of the following characteristics cannot be observed in the progeny if linkage is present?

The first mutant gene reported by $T.H. Morgan$ in $Drosophila$ was the . . . . . . .

In a fruit fly,the $X$-chromosome linkage map has a total length of $66$ units,with the yellow body gene $(y)$ at one end and the bobbed hair gene $(b)$ at the other end. What will be the recombination frequency between these two genes $(y$ and $b)$?

Alleles of different genes that are on the same chromosome may occasionally be separated by a phenomenon known as

Who performed the first experiment on linkage and recombination?

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