Archive | 2014

One more lookup (humor from Esto)

It was midnight and I just wanted to follow one one more ancestry green leaf clue, this led to some fascinating discoveries about an 8th grandfather in Seljford Norway. Then I had to double check my copies of the farmbook pages and make a note on my list of lookups to do next Salt Lake City visit. Then click another leaf…

Would you believe when I looked at the time again it was two in the morning? So you can understand why this Esto cartoon really had me laughing.

Genealogy humor from Esto Frigus
Image from geneapalooza used by permission

The DNA behind the PBS show “Finding Your Roots”

On Tuesdays, I usually count down the hours until the latest episode of Finding Your Roots is on, but tonight we will be watching election returns while my DVR records the show. So you all know what I will do when my husband finally heads for bed …

FindingRootsBlog

It looks like tonight’s show will showcase the ancestry of a number of jewish celebrities. Since Ashkenazi research can be particularly difficult and the DNA very tricky due to that population’s endogamy, I am particularly interested to see what I can learn.

 

Cece Moore‘s latest blog entry at the PBS site was just posted. Each week she discusses some of the details of the DNA work she did for the previous show.
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When is a DNA segment match a real match? IBD or IBS or IBC?

The current technology for personal genome testing cannot tell you which of the two chromosomes, maternal or paternal, in a pair that an allele comes from. It can tell you that there is an AG at a specific position and a CT at the next position but not whether the A came from your mother or your father. This leads to much confusion about DNA segment matching.

ShipleyKittyDancingSmll

Kitty and Shipley; siblings sharing 47% of their DNA

The matches that these testing companies find are for stretches of DNA that are half identical regions (HIRs). This is due to the fact that a relative who shares a DNA segment from a common ancestor with you will match you along the chromosome you got from the parent who is descended from that ancestor. Thus your new relative will match you for half the alleles in those positions. Only a sibling will share fully identical regions of DNA. Click here for a page that has a picture of the DNA I share with my brother Shipley.

For example, if my Dad gave me AAAAAAAAAAA and my Mom gave me CCCCCCCCCCC then I would seem to match absolutely everyone on that segment because every position has both an A and a C. So an ACACCAACCAC or a CCAACCCACA looks like a match, but only those with an  AAAAAAAAAAA or a  CCCCCCCCCC would be real matches. This is simplistic and the segment runs used for matching are much longer than this to try to avoid that sort of false matching. Also note than when your testing company shows an AC it is really an AT and a CG but just one of the known pairing is shown for brevity.

The term for a real match is IBD, which is an abbreviation for Identical By Descent. The term IBS means Identical by State which would apply to any false match. So in our example, the CCAACCCACAA match would be considered IBS.

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New Utilities at GEDmatch: Tier 1 for paid members

There are four exciting new utilities at GEDmatch.com which I plan to cover in depth over the next several days. These are only available to for people who have donated  at least $10 (every additional $10 gets you these for another month). A good way for GEDmatch to pay for their extra server costs. The rest of the site will remain free. The utilities are:
Tier1

  1. A Matching Segment Search – Get a list of all your segment matches suitable for cutting and pasting into a spreadsheet
  2. A Relationship Tree projection – calculates probable relationship paths based on Autosomal and X-DNA Genetic Distances. It is experimental, try it and give them feedback
  3. Lazarus – Construct a kit to represent a close ancestor, wow!
  4. Triangulation – takes your top 300 matches and finds which ones match each other with details. The format can be copied to a spreadsheet

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