Recombination, the process by which a molecule of (usually) DNA is broken and joined to another one, is one of the main sources of genetic diversity in sexual organisms. Meiotic recombination takes place during the meiotic division (which gives rise to the gametes), and through the process chromosomes show crossover (see figure 1).
Figure 1: An illustration of crossing over during the meiotic division.(Source: http://www.britannica.com)
Previous research has shown that the rate of this meiotic recombination exhibits a fair amount of variation between different species, and even between individuals. Genetic experiments have illustrated that there must be a heritable component related to this recombination rate, but the exact nature of this component remained elusive.
A new study (Dumont and Payseur, 2011) used two closely related subspecies of house mice (Mus musculus musculus and M. m. castaneus) to investigate this variation in recombination rate. Between the males of these subspecies, a rather large difference (roughly 30%) in recombination rate was reported. By interbreeding these two subspecies, a hybrid F2 generation was formed, which showed great variation in recombination rate. Much of this variance could be explained by eight quantitative trait loci, of which two can be found on the X chromosome (see figure 2), which might explain why the females in the F2 generation displayed minimal divergence (about 5%) in recombination rate. These results provide an initial understanding of the genetic differences that may lie at the base of the sometimes rather large difference in recombination rate between species, subspecies, and even individuals.
Figure 2: The eight quantitative trait loci (including 2 on the X chromosome) that explain the difference in recombination rate. (LOD stands for logarithm of odds, and is used for the estimation of recombination frequency. Usually, a LOD score of over 3 is considered to be evidence for linkage, in this case between a genetic marker and recombination rate.)
(Source: Dumont and Payseur, 2011)
Dumont, B.L. and Payseur, B.A. (2011). Genetic Analysis of Genome-Scale Recombination Rate Evolution in House Mice. PLoS Genetics. 7(6): e1002116. doi:10.1371/journal.pgen.1002116.(Click here for the original article).