Mammalian recombination hot spots: properties, control and evolution

Key Points Recombination events in many organisms are concentrated in highly localized areas termed 'hot spots'. Hot spots can be detected by statistical analysis of genetic variation, analysis of pedigrees and analysis of sperm genomes. Hot spot activities vary in orders of magnitude and can show sex specificity and imprinting effects. The location and relative activity of hot spots is determined by both their own DNA sequence, acting in a cis manner on each chromatid, and by trans -acting factors, such as the zinc finger histone trimethylase PR domain-containing 9 (PRDM9). The two sexes differ in their overall recombination activity and the distribution of crossing over along individual chromosomes. Total recombination activity is genetically regulated and is affected by the number of chromosomes and chromosomal arms in each species. Recombination hot spots evolve rapidly. This article describes the important advances in our understanding of recombination in humans and mice, from the properties and activity of individual hot spots to the control of the recombination landscape along chromosomes and between the sexes. Recombination, together with mutation, generates the raw material of evolution, is essential for reproduction and lies at the heart of all genetic analysis. Recent advances in our ability to construct genome-scale, high-resolution recombination maps and new molecular techniques for analysing recombination products have substantially furthered our understanding of this important biological phenomenon in humans and mice: from describing the properties of recombination hot spots in male and female meiosis to the recombination landscape along chromosomes. This progress has been accompanied by the identification of trans -acting systems that regulate the location and relative activity of individual hot spots.