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

Linkage was first suggested by

Two genes '$a$' and '$b$' show $20\%$ recombination. What will be the proportion of gametes produced by a dihybrid $F_1$ individual with the genotype $++/ab$,derived from a cross between $++/++$ and $ab/ab$?

$T.H.$ Morgan worked with $Drosophila$ to prove the chromosomal theory of inheritance. Which of the following characteristics was $NOT$ present in $Drosophila$?

When two genes are situated very close to each other in a chromosome,

Genetic recombination occurs through