Wikipedia:Reference desk/Archives/Science/2015 January 8

:::There actually is a portion of the Y chromosome, the [[pseudoautosomal region]], that can recombine with the corresponding portion of the X chromosome. It only comes to about 5% of the Y chromosome, though. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 16:31, 9 January 2015 (UTC)

:::There actually is a portion of the Y chromosome, the [[pseudoautosomal region]], that can recombine with the corresponding portion of the X chromosome. It only comes to about 5% of the Y chromosome, though. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 16:31, 9 January 2015 (UTC)

:One thing to clarify: First, let's ignore things that can alter the 50% from each parent (the things Medeis mentions, but also genetic disorders like [[XXY]] or [[XYY]], etc), and focus on the simplified 50/50 model of genetic inheritance from each parent for alleles in [[nuclear DNA]]. Now, a parent is ''guaranteed'' to share 50% of your [[allele]]s ('' '''not'' [[gene]]s''', let's be precise here :), and cannot share any more or less unless you get into edge cases. We don't know exactly which alleles are shared, in part due to [[recombination]]. In contrast, a sibling shares 50% as an [[expected value]]. So the situation is this - if you want a "safe bet" for most shared alleles, pick a parent, you'll never be far off from 50%. If you want to potentially maximize the shared alleles, pick a sibling, who will share more than 50% of alleles roughly half the time. As Lindert points out above, a sibling has the ''potential'' to share much more than 50% with you, but can also be lower, and this makes for some interesting differences, depending on our motive for finding a highly similar person. [[User:SemanticMantis|SemanticMantis]] ([[User talk:SemanticMantis|talk]]) 16:41, 9 January 2015 (UTC)

:One thing to clarify: First, let's ignore things that can alter the 50% from each parent (the things Medeis mentions, but also genetic disorders like [[XXY]] or [[XYY]], etc), and focus on the simplified 50/50 model of genetic inheritance from each parent for alleles in [[nuclear DNA]]. Now, a parent is ''guaranteed'' to share 50% of your [[allele]]s (''' ''not'' [[gene]]s''', let's be precise here :), and cannot share any more or less unless you get into edge cases. We don't know exactly which alleles are shared, in part due to [[recombination]]. In contrast, a sibling shares 50% as an [[expected value]]. So the situation is this - if you want a "safe bet" for most shared alleles, pick a parent, you'll never be far off from 50%. If you want to potentially maximize the shared alleles, pick a sibling, who will share more than 50% of alleles roughly half the time. As Lindert points out above, a sibling has the ''potential'' to share much more than 50% with you, but can also be lower, and this makes for some interesting differences, depending on our motive for finding a highly similar person. [[User:SemanticMantis|SemanticMantis]] ([[User talk:SemanticMantis|talk]]) 16:41, 9 January 2015 (UTC)