Page 11 - O Mahony Journal 2025

A child will inherit mtDNA only from their mother, as mtDNA is passed down through a
mother’s egg.

Therefore, both men and women carry their mother’s mtDNA, but only women will pass
that mtDNA down to the next generation.

This is different than Y-DNA, which is exclusive to males and passed down from their
fathers, meaning that both women AND men can complete an mtDNA test.

• mtDNA Benefits and Challenges

Mitochondrial DNA testing offers several important benefits to genealogy researchers.
There is very little recombination, or change, of mtDNA as it passes down through the
generations.

This allows a researcher to use mtDNA results to trace a matrilineal line from mother,
grandmother, great-grandmother, and so on.

When reviewing mtDNA cousin matches, a significant mismatch can rule out a relationship
on that matrilineal line.

Adoptees may benefit from completing an mtDNA test, as the results can point them
towards their biological mother’s family.

• mtDNA Testing

Testing companies have broken the circular mtDNA, or genome, into three different
sections, giving each section a different name:

1. Hypervariable control region 1 (HVR1)
2. Hypervariable control region 2 (HVR2) – Both of these regions are more
likely to change from one person to the next unless those people are closely
related. This makes HVR1 and HVR2 ideal for genealogical testing.
3. Coding Region (CR) — The largest area of the genome, the coding region
changes much less frequently.

There are two different ways to test these mtDNA regions:

1. mtDNA Sequencing: This type of test can sequence either all or a portion
of the mtDNA genome. Sequenced sections consist of series of the four
different nucleotide base pairs (adenine, cytosine, guanine, and thymine),
identified by the letters A, C, G, and T, respectively. High-resolution tests
are also referred to as “Full Sequence” testing and are recommended
over low-resolution tests for genealogical purposes.

2. SNP Testing: An SNP, or “single nucleotide polymorphism,” is a change
to one nucleotide in a DNA sequence at a specific location on the genome.
For example, T (thymine) has changed or mutated to C (cytosine) at
position 15,833. The test will look at hundreds or thousands of locations
on the genome for SNPs. The more two people are related, the more
SNPs they have in common.

11