Well I've got a gal, she's as cute as she can be; she's a distant cousin but she's not too distant with me; we'll kiss all night, I'll squeeze her tight; but we're kissin' cousins and that's what makes it all right - All right, all right, all right.
" // According to a leading researcher in the use of autosomal DNA for genealogical purposes, autosomal testing can identify cousins you don't even know you have.
There are four major types of DNA that are used for genealogical purposes: 1) autosomal DNA, 2) the Y chromosome, 3) the X chromosome, and 4) mitochondrial DNA.
This article explores autosomal DNA in greater depth.
The majority of our DNA is autosomal.
This DNA is found in 44 of our 46 chromosomes.
Autosomal DNA is highly useful for genealogical purposes.
As a general rule, the more autosomal DNA that you share in common with another person, the more closely related you are to that person.
A child receives 50% of their autosomal DNA from each of their parents, and similarly on average a child receives a 25% contribution to their DNA from each of their four grandparents.
So it goes as you go back through each generation until you reach a point about six to seven generations back where there is no guarantee that you will inherit a segment of DNA from each ancestor in your family tree at that level, due to the random nature in which individual blocks of autosomal DNA are passed down from parent to child.
It is also important to have some understanding about the percentage of autosomal DNA that siblings, first cousins, and other more-closely related relatives share in common with one other.
Generally speaking, siblings share 50% of their DNA, and first cousins share about 12.
5% of their DNA, on average.
However, these percentages can vary somewhat widely with some siblings sharing 60% or more of their DNA in common, while other siblings only share 40% or less.
Similarly, first cousins can share as little as 7% of their autosomal DNA or as much as 15%.
There are currently three primary genetic genealogy companies that offer autosomal DNA testing for genealogical purposes: 23andMe, Family Tree DNA (FTDNA), and Ancestry.
All three companies provide you with a list of closest matches in their databases.
The number of matches that you will have depends on the number of people in the company's database, the number of people with your ancestral background who have been tested, and the criteria that the company sets for what constitutes a match.
The exciting thing about autosomal DNA testing for genealogical purposes is that this type of testing can identify cousins that you have not previously known about.
Many of these cousins are distantly related to you, but some may be closely related.
If you carefully study the pedigree charts of your genetic cousins, in some cases you can identify surnames or ancestors that you share in common with these matches.
If you can identify specific DNA segments that you share in common with two or more people, then careful review of those people's pedigree charts can potentially help you identify shared surnames that can help you break through genealogical brick walls.