Two methods of genetic recombination

    Unlinked loci on separate chromosomes (A & B vs C) segregate independently according to Mendel's Rules: the recombination fraction is 50%Linked loci on the same chromosome (A & B) do not recombine, unless there is a physical exchange of genetic material as the result of a crossover, seen as a cytological chiasma (plural, chiasmata). Recombination frequency will be 0 ~ 50%, depending on whether or not a crossover occurs between the loci. This is turn varies according to how closely the loci are situated.

Figure ©2002 by Griffiths et al.; all text material ©2010 by Steven M. Carr