Complete linkage is observed in.....

$A$ test cross of an $F_1$ fly $+a/+b$ produces the following offspring:
$++/ab = 9$
$ab/ab = 9$
$+b/ab = 41$
$a+/ab = 41$
What is the distance between the linked genes?

In order to calculate the map distance of genes on a chromosome,one must know the:

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

How many types of gametes will be produced by a male Drosophila having the following arrangement of two genes ($y$ and $w$) on the $X$-chromosome?

What was the phenotypic ratio obtained in the experiment on linkage and recombination performed in Lathyrus odoratus (Sweet Pea)?