High-resolution mapping with tiling arrays of meiotic crossovers and non-crossovers in yeast

Wolfgang Huber
Afternoon Session, 1 September (11th MGED Meeting, 1-4 September, 2008)

Meiotic recombination is important for proper chromosome segregation and is an important mechanism in evolution in sexual organisms. It is initiated via double-strand breaks, and then there are two different pathways: CO and NCO (crossover and non-crossover). They are mapping all recombination events in 50 x 4 tiling arrays for the child strains.

Identified 179 recombination hot spots – none overlapped the centromere, as expected. 85% overlapped a promoter, but only about 25% of bases in hot spot intervals overlap promoters, while 68% overlap coding sequences. There were a wide variety of recombination events, some much more "messy" than the normal textbook events. They compared their hotspot maps with some older ds break maps made last year by a different group, to determine correlation between DSB and their recombination hotspots. There was a pretty close correlation. They concluded from analysing the data that genome-wide distributions of CO and NCO hotspots are different (p < 0.0005).

They found correlation between hotspot location and the genes that are transcribed from these regions (genes with distinct expresssion profiles are associated with hotspots and hotspot subtypes). Hotspots tend to be GC-rich. Up to 1% of a meiotic product's genome is subject to conversion per single meiosis. conversion favors GC. Per meiosis, 2.1% of polymorphic positions are converted to the opposite genotype. However, hotspots are also more diverse. Allelic Homogenization appears to be counteracted by other forces, e.g. mutagenicity of recombination evens. Distinct distributions of CO and NCO suggest that genomic position affects DSB resolution. There is inference between NCO and COs. Conversion hotspots unlink genomic regions from the linkage map.

These are just my notes and are not guaranteed to be correct.
Please feel free to let me know about any errors, which are all my
fault and not the fault of the speaker. 🙂

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