During meiosis, maternal and paternal chromosomes undergo exchanges by 
homologous recombination. This is essential for fertility and contributes to 
genome evolution. In many eukaryotes, sites of meiotic recombination, also 
called hotspots, are regions of accessible chromatin, but in many vertebrates, 
their location follows a distinct pattern and is specified by PR 
domain-containing protein 9 (PRDM9). The specification of meiotic recombination 
hotspots is achieved by the different activities of PRDM9: DNA binding, histone 
methyltransferase, and interaction with other proteins. Remarkably, PRDM9 
activity leads to the erosion of its own binding sites and the rapid evolution 
of its DNA-binding domain. PRDM9 may also contribute to reproductive isolation, 
as it is involved in hybrid sterility potentially due to a reduction of its 
activity in specific heterozygous contexts.