Abby Dernburg was the lead author on the paper. The critical protein, Spo11, cuts DNA strands to allow the genetic shuffling to take place. Eggs or sperm with the wrong numbers of chromosomes will form embryos that either miscarry or develop disorders such as Down syndrome. Ultimately, basic research into meiosis could help clarify the root causes of Down syndrome and several other serious birth defects. The newly published study represents a significant step in that direction, she said.
Sexual reproduction combines an egg and a sperm.
But the first stage of meiosis, when recombination occurs, is the opposite of this process. Here the number of chromosomes in a cell is halved, so each egg or sperm has only one copy of each. This first phase of meiosis is when a developing egg or sperm cell is most likely to make mistakes in distributing one of each chromosome to its two daughter cells. In humans, these errors usually result in spontaneous abortion because the developing embryo cannot survive. But some errors are not lethal.