Thomas Hunt Morgan worked on which of the following organisms?

What happens in the process of variation?

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?

Which scientist explained linkage and recombination in Drosophila?

In a certain plant, red flowers $(R)$ are dominant to white flowers $(r)$ and tallness $(T)$ is dominant to dwarfness $(t)$. $A$ heterozygous plant $(RrTt)$ is backcrossed with a double recessive plant $(rrtt)$. If the gene loci for colour and size are situated very close together on the same chromosome, the expected percentage of offspring could be approximately:

Tall Red

Tall White

Dwarf Red

Dwarf White

respectively.

In diploid organisms,crossing over is responsible for which of the following?