Editing Sibling (section)

===Percentage distribution===
In practice, full siblings do not share exactly 50% of their DNA, as [[chromosomal crossover]] only occurs a limited number of times and, therefore, large chunks of a chromosome are shared or not shared at one time. In fact, the mean DNA fraction shared is 50.28% with a standard deviation of 3.68%,<ref>{{cite journal | pmc=4037293 | year=2013 | last1=Vinkhuyzen | first1=A. A. | last2=Wray | first2=N. R. | last3=Yang | first3=J. | last4=Goddard | first4=M. E. | last5=Visscher | first5=P. M. | title=Estimation and Partitioning of Heritability in Human Populations using Whole Genome Analysis Methods | journal=Annual Review of Genetics | volume=47 | pages=75–95 | doi=10.1146/annurev-genet-111212-133258 | pmid=23988118 }}</ref> meaning approximately 1/4 of sibling pairs share more than 52.76% of their DNA, while 1/4 share less than 47.8%.<ref>Calculated based on the [[Standard deviation#Rules for normally distributed data|normal distribution]]</ref>

There is a very small chance that two half-siblings might not share any genes if they didn't inherit any of the same chromosomes from their shared parent. This is possible for full-siblings as well, though even more unlikely. But because of how [[homologous chromosomes]] swap genes (due to [[chromosomal crossover]] during [[meiosis]]) during the development of an egg or sperm cell, however, the odds of this ever actually occurring are practically non-existent.<ref name="Ask a Geneticist 2013"/>