% Shared DNA (expectations)

www.isogg.org/wiki/Autosomal_DNA_statistics

This graphic assumes that relatives share two common ancestors.

How would expectations change if there were only one common ancestor?

Kinship - Coancestry vs Covariance

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Shared chromosome segmentsChild #1

Child #2

Mom (Dam) Dad (Sire)

1. What % of the DNA is expected to be shared between the two children? (this is covariance)

2. What would be the expected level of inbreeding in an offspring of Child #1 and Child #2? (this would be equal to their coancestry)

3. 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?

100 cM

From Grandpa

From Grandma

Full-sib Covariance

A1A3 A1A4 A2A3 A2A4

A1A3 1/16

A1A4 1/16

A2A3 1/16

A2A4 1/16

Shared chromosome segments

25 2525

100 cM

Chance of no shared alleles?

A1A2 A3A4

Child #2

Child #1

Expectations

Half-IBD 50 cMFull-IBD 25 cMAt least one match 75 cMNo Match 25 cM

2

D412

A212

FSFSCov

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