The number of linkage groups in $Pisum \text{ } sativum$ is

Define/Explain the following terms:
$1.$ Linked genes
$2.$ Locus

Why did Morgan choose the fruit fly for his experiments to prove the chromosomal theory of inheritance?

Sex linkage was first observed by.....

Discuss in detail the contributions of Morgan and Sturtevant in the area of genetics.

In $Drosophila$,crossing over occurs in females but not in males. Genes $A$ and $B$ are located on a chromosome at a distance of $10 \ cM$. The genotype of the female $Drosophila$ is $AB/ab$ and the genotype of the male $Drosophila$ is $AB/ab$. How many types of gametes are produced by the female and male $Drosophila$,respectively?