Page 10 - O Mahony Journal 2025

Moving from simple to more complex material, John then brought us to a more in-depth
exploration of each type of DNA.

Autosomal DNA (atDNA)Test

Your autosomal DNA (atDNA) is a mixture of the DNA you received from your parents
(about 50% from your mother and 50% from your father). Unlike Y-DNA or mt-DNA,
which is passed from one generation to another generally intact, each person’s
autosomal DNA is unique.

An autosomal DNA test provides you with a breakdown of your ethnic makeup and
is designed to help you find relatives on either side of your ancestral lines within
the last five generations.

If you are trying to confirm a relationship with someone who is a third cousin or closer,
the atDNA test is recommended.

Based on the amount of autosomal DNA shared between two individuals (both
lengths of chromosomal segments and number of segments), we’re able to determine
when those individuals should have shared a common ancestor. However, different
amounts of shared autosomal DNA can indicate many different shared relationships,
and the random recombination factor can make individuals appear more closely or
more distantly related than they are. Typically, this test can be used to find relatives
that share a common ancestor within about five generations.

The strengths of an atDNA test are that it may be used with equal success by both
men and women and its ability to find connections on any of your family lines. The
challenge is determining which branch of your family tree you share with your cousin.
This can be accomplished with traditional genealogical records and by utilizing other
types of DNA tests and analytical tools.

For additional information, this article may be of some help: https://help.familytreedna.com/hc/en-us/
articles/4411203169679-Our-Autosomal-DNA-Test-Family-Finder-

[Ed. Note: The above link is for information purposes and does not constitute a recommendation or any other relationship
between Family Tree DNA and The O Mahony Society.]

Mitochondrial DNA (mtDNA)

mtDNA is found outside the nucleus of each of your cells in cellular organelles called
mitochondria (the “powerhouses” of our cells). Almost every cell in your body contains
hundreds to thousands of copies of the mtDNA molecule.

This differentiates mtDNA from autosomal DNA, Y-DNA, and X-DNA, whose genetic
data is in the 23 pairs of chromosomes residing within the cell’s nucleus.

Mitochondrial DNA is actually circular in shape, made of over 16,500 pairs of DNA
molecules called nucleotides, which help produce energy for each cell.

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