% Shared DNA (expectations) Parents always give 50% of their genes to their offspring. Other relationships would be reduced by ½ for half-siblings, half-aunts/uncles, etc. Remember that these values are actually a range (not a single value) This graphic assumes that relatives share two common ancestors. How would expectations change if there were only one common ancestor? www.isogg.org/wiki/Autosomal_DNA_statistics

Kinship - Coancestry vs Covariance Dad (Sire) Mom (Dam) From Grandpa From Grandma 100 cM X Shared chromosome segments Child #1 In Plant Breeding – the female is always listed first (not so in human genealogy). Full IBD = 25 cM, ½ IBD = 50 cM, full + half = 75 cM Child #2 What % of the DNA is expected to be shared between the two children? (this is covariance) What would be the expected level of inbreeding in an offspring of Child #1 and Child #2? (this would be equal to their coancestry) If both children are DNA tested (they are humans now), how many cM are expected to be IBD on both chromosomes (full-IBD)? On just one chromosome (half-IBD)? If the test does not distinguish full and half IBD, what is the total cM that are expected to match?

Full-sib Covariance 25 25 25 A1A2 X A3A4 Expectations Half-IBD 50 cM Shared chromosome segments 25 25 25 A1A2 X A3A4 100 cM Expectations Half-IBD 50 cM Full-IBD 25 cM At least one match 75 cM No Match 25 cM Chance of no shared alleles? Child #2 A1A3 A1A4 A2A3 A2A4 1/16 Child #1