DNA double-strand break formation and repair in Tetrahymena meiosis.

The molecular details of meiotic recombination have been determined for a small number of model organisms. From these studies, a general picture has emerged that shows that most, if not all, recombination is initiated by a DNA double-strand break (DSB) that is repaired in a recombinogenic process using a homologous DNA strand as a template. However, the details of recombination vary between organisms, and it is unknown which variant is representative of evolutionarily primordial meiosis or most prevalent among eukaryotes. To answer these questions and to obtain a better understanding of the range of recombination processes among eukaryotes, it is important to study a variety of different organisms. Here, the ciliate Tetrahymena thermophila is introduced as a versatile meiotic model system, which has the additional bonus of having the largest phylogenetic distance to all of the eukaryotes studied to date. Studying this organism can contribute to our understanding of the conservation and diversification of meiotic recombination processes.