Sticky fingers

A single protein recognizes different sequences in different organisms and drives speciation.

Computer graphic of a two zinc-finger peptide (yellow) binding to a DNA (red and blue) molecule.

Homologous recombination physically links together chromosomes at the first division in meiosis by sharing DNA strands between chromosomes. This creates genetic variation in organisms that reproduce sexually, and makes sure that homologous chromosomes segregate correctly into the daughter cells. But recombination does not appear to be random: it tends to cluster within specialized 1- to 2-kb-long sites called “hotspots.”

It’s logical then to ask what specifies or controls hotspot location. Scientists have gathered evidence that three different mechanisms are involved in controlling location and activity. First, the genomic sequence around each hotspot seems to be important; for example, 40 percent of human hotspots are associated with a repeating 13-basepair motif. However,...

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