Question

If the four genes A, B, C and D are 5, 10 and 30 Map units away from each other respectively and arranged in the same manner in a chromosome, which two genes would likely show more recombination?

Answer 1

Crossing over is the exchange of genetic materials between two non-sister chromatids of two homologous chromosomes by forming chiasmata.
Linkage is the tendency of genes in a chromosome to stay together and crossing over is inversely proportional to the linkage. More the distance between the linked genes, more will be the chances of crossing over, and hence more recombinants will be produced.
In the question given, genes C and D have the highest distance in between them, so they will show the maximum recombinations among the 4 linked genes.