DNA for

Genealogical Research

Oakmont Genealogy Club - January 24, 2022

DNA is a double helix – Watson, Crick, Franklin

Chromosome 23 is different - it defines whether the embryo is male or female

23 chromosome pairs

History of DNA testing

1987 - First successful forensic DNA test to identify a criminal

2000 - Family Tree DNA offered the first Y DNA test

2000 - Family Tree DNA offered the first mitochondrial DNA (mtDNA) test

2005 - National Geographic “Genographic” project to test ethnic background

2007 - 23andme offered the first autosomal DNA test for genealogy (23andme was founded to identify whether you carry a genetic modification which has medical implications)

Today - estimated 50 million people have been tested, most for autosomal DNA (15 million at Ancestry and 13 million at 23andme)

Autosomal DNA - Finding Identical By Descent (IBD)

How do you get your DNA?

You purchase a test kit from one of the companies (Ancestry - $99 normal) Most companies have frequent sales (recent Ancestry was $59)

Most tests involve a swab placed inside the mouth, sealed in a tube, and mailed back to the company

In a few weeks you receive your results. While all companies give you top line results, many require you to subscribe to an ongoing service in order to get their best analytical support

What are centiMorgans (cM)

An analytical method to estimate closeness

What is a centiMorgan (cM)?

Your DNA is not only broken into Chromosomes, it also is associated with single nucleotide polymorphisms, commonly called SNPs.

The DNA analysis companies start by looking for SNPs in your DNA that match someone else’s SNP.

A centiMorgan, commonly called cM, is where the SNPs in a sequence of DNA are likely to change every 100th generation, giving a 1% chance of changing in one generation. The DNA analysis companies have chosen 6,800 cM to examine.

By looking at how many cM match, they can estimate your relationship.

Note that each generation has half of the previous generation. So if you and another person were 1st cousins (850 cM) then your child would be a 1C1R or 425 cM. His child and your child would be second cousins so the number is ¼ or 212.5.

Let’s Look at Actual DNA Matches

When you find your relationship with a new match

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Check the cM to see if it seems to be the right level

Make a note on the match (helps when you’re doing shared matches)

Consider contacting the individual to see if they have more information For close matches, they might even have pictures!

Update your own tree to include the individual who is the new match

Enter this new relationship in your DNA database

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Non Paternal Events

It is said that 3% of all births are “non-paternal”

That includes adoptions (both formal and informal)

Illegitimate births when there is no father present

Illegitimate births that are claimed by another mother (usually a grandmother or aunt)

Births during marriage where the biological father is not the marital partner of the woman

Finding Other People’s Family Trees

Check to see if they have a family tree available

On Ancestry, they may have a public tree but just haven’t connected to it

Email/message them (some will respond)

It helps if you can suggest a possible relationship (you match my Lilly family)

Search their names and codenames (HogDave) on Ancestry or other sites

Search their names, codenames, and email addresses on Google

Build out their tree yourself

DNA for

Genealogical Research

Oakmont Genealogy Club - January 24, 2022