What do genetic maps represent?

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

The map distance between genes $A$ and $B$ is $3$ units,between $B$ and $C$ $10$ units,and between $C$ and $A$ $7$ units. The order of the genes in a linkage map constructed on the above data would be:

What is the name of the pea species used by Bateson and Punnett in their experiments?

Mendel did not recognize the linkage phenomenon in his experiments because

What is the reason for the absence of hybrids?