But if you look at the number of DNA segments, they will be quite different between parent/child and sibling. I share 23 segments with my son, spanning the entire chromosomes, and with my brothers I share 42 and 49 segments, broken up across the chromosomes. One brother is ~53% and one ~44%.
Furthermore, with my son all of the segments are half-identical, whereas with my brothers the half-identical segments have sections that are completely identical (meaning that in that area we got the same bit from Dad and the same bit from Mom, rather than one or the other). With one brother I have 42 segments (3014 centimorgans) that within them contain 43 completely identical segments (total 931 cM out of the 3014). With the other I have 49 segments (2534 cM) that within them contain 26 completely identical segments (708 cM). With my son, a much simpler result: 23 segments, 3719 cM, no completely identical segments. My brothers share with each other 43 segments, 3027 cM, within those 39 segments completely identical, 1062 cM.
(Note: It's not impossible for parent and child to have stretches of completely identical DNA, but it would imply that the tested parent was genetically related to the child's other parent.)
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Furthermore, with my son all of the segments are half-identical, whereas with my brothers the half-identical segments have sections that are completely identical (meaning that in that area we got the same bit from Dad and the same bit from Mom, rather than one or the other). With one brother I have 42 segments (3014 centimorgans) that within them contain 43 completely identical segments (total 931 cM out of the 3014). With the other I have 49 segments (2534 cM) that within them contain 26 completely identical segments (708 cM). With my son, a much simpler result: 23 segments, 3719 cM, no completely identical segments. My brothers share with each other 43 segments, 3027 cM, within those 39 segments completely identical, 1062 cM.
(Note: It's not impossible for parent and child to have stretches of completely identical DNA, but it would imply that the tested parent was genetically related to the child's other parent.)