Recombination is the exchange of DNA segments between the two copies of a chromosome (maternally inherited and paternally inherited). This occurs during the creation of an egg or sperm for the next generation. Each chromosome is cut at the same location, usually at one or two random spots (crossover points), and DNA segments are swapped between the two copies.
The newly formed chromosome in the egg will be a patchwork of contributions from the maternal grandparents, and the newly formed chromosome in the sperm will be a patchwork of contributions from the paternal grandparents, but there is still one copy of every gene. Some eggs and sperm will retain a complete copy of one grandparent's chromosome without recombination. The creation of each egg and sperm is an independent event, so siblings will inherit different portions of their grandparents' DNA.
Males and females have different rates of recombination. Males average about 27 crossovers per child and females average about 41 crossovers per child.
- Campbell CL, Furlotte NA, Eriksson N et al (2015). Escape from crossover interference increases with maternal age. Nature Communications 6; article number 6260.
- Chowdhury R, Bois PRJ,Feingold E, Sherman SL, Cheung VG. Genetic analysis of variation in human meiotic recombination. PLoS Genetics 2009 September; 5(9): e1000648.
- Fledel-Alon A, Wilson DJ, Broman K et al. Broad-scale recombination patterns underlying proper disjunction in humans. PLoS Genetics 2009 September; 5(9): e1000658.
- Recombination: creating variation in gametes An illustrated article on the Genetics Suite website.
- Recombination also evolves by Razib Khan The Unz Review, 18 January 2015.
- Autosomal testing: recombination by Steve Handy. DNA Genealogical Experiences and Tutorials blog, 3 November 2012.
- How do DNA segments get smaller? by Blaine Bettinger. The Genetic Genealogist, 31 January 2015.