DNA Research #DNA RE: What numbers are significant #dna

Sarah L Meyer

Dear Genners,
Someone had sent me this information:
According to Matt Dexter, on the FTDNA Forum, here is a breakdown of sum
shared DNA ranges for various relationships:

Parent/child: 3539-3748 centimorgans (cMs)
1st cousins: 548-1034 cMs
1st cousins once removed: 248-638 cMs
2nd cousins: 101-378 cMs
2nd cousins once removed: 43-191 cMs
3rd cousins: 43-ca 150 cMs
3rd cousins once removed: 11.5-99 cMs
4th and more distant cousins: 5-ca 50 cMs

And >from Tim Janzen on the Genealogy-DNA listserv

Ranges of the length of shared IBD segments based on family

Parent/child: 285
1st cousins: 50-141
1st cousins once removed: 36-106 cMs
2nd cousins: 21-64 cMs
2nd cousins once removed: 19-81
3rd cousins: 13-77
3rd cousins once removed: 0-27
4th cousins: 0-22
4th cousins once removed: 0-13
5th cousins: 0-27

Also I have now tested 9 cousins and am waiting for results >from two more.
These numbers helped me to revise some family relationships. I will
provide you with some examples:
Relationship to me Shared Longest Block

1st cousin 857.13 75.76
1st cousin 1 R 363.51 41.53
2nd cousin 444.01 74.79
2nd cousin 266.56 39.7
1/2 2nd cousin 236 42.6
1/2 2nd cousin 146.33 44.83
1/2 2nd cousin 119.74 30.00
1/2 2nd cousin 1 R 86.4 8.41
1/2 2nd cousin 58.5 11.49

You will notice a significant variation in the numbers. In order to get
the values for the 1/2 cousins just take the ranges and divide by 2. Two of
my second cousins became 1/2 second cousins after the DNA testing due to a
previously unknown "husband" of my great grandmother. Also the DNA
confirmed that my second cousin once removed was actually my 1/2 second
cousin once removed- but here there is some paper trail evidence for an
older sibling and a younger sibling having different mothers (and my
ancestor and his are middle siblings. Also according to FT DNA I am 100%
Ashkenazic, so the FT DNA algorithm is different for suggested values for us
due to inbreeding.

Sarah L M Christiansen
Georgetown TX

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