Two linked genes show a recombination frequency of 10 per cent. The distance between them on the chromosome map is

Explanation

One map unit, or centimorgan, is defined as a recombination frequency of one per cent, so ten per cent recombinants means ten map units apart. The logic is that the further apart two genes lie, the more likely a chiasma forms between them. Frequencies above fifty per cent are never observed, because at that point the genes assort as though unlinked.