DNA Lesson Series: The mtDNA and its role in Ancestry
mtDNA Part I - mtDNA 101
mtDNA Part II - Facts about mtDNA
mtDNA Part III - mtDNA Structure
mtDNA Part IV - Ancestral Markers
mtDNA Part V - Detecting Mutations in the mtDNA
mtDNA Part VI - mtDNA Ancestral Markers  <<– you are here
mtDNA Part VII - The Cambridge Reference Sequence
mtDNA Part VIII - mtDNA Test Types
mtDNA Part IX - mtDNA Haplogroup Determination
mtDNA Part X - mtDNA Subclades
mtDNA Part XI - mtDNA Haplogroup H
mtDNA Part XII - Subclades of mtDNA Haplogroup H
mtDNA Part XIII - Distribution of Subclades of H
mtDNA Part XIV - Descendents of Maria-Theresa
mtDNA Part XV - Luke the Evangelist
mtDNA Part XVI - Empress Feodorovna
mtDNA Part XVII - James “Earthquake McGoon” McGovern

In this blog, we will take a look at how the mutations in our mtDNA act as ancestral markers which allow us to trace our ancestry.

We all have a unique pattern of SNP mutations in our mtDNA.  Our SNP mutations can be used to trace our maternal ancestry in two ways:  1) Direct Comparisons, and 2) Haplogroup Determination.  Let’s talk about each one in more detail. 

1.  Direct Comparisons: 

By testing your mtDNA, you will discover the unique set of mutations that was passed down to you from your maternal ancestors along your direct maternal line.  Your mtDNA “profile” is the unique set of mutations that you inherited from your own mother, and it is unique to your maternal ancestry.  For example, all other descendents living anywhere in the world today who are direct descendents of the same branch of the “haplogroup tree” as you, will have exactly the same mtDNA profile as you (ie. you are linked through a common maternal ancestor).  Likewise, if someone does not have the same mtDNA profile as you, that means that he/she definitely did not descend from the same maternal line as you (ie. you are not directly linked on your maternal line).  Once you test your mtDNA markers, you can:

• Use your markers to confirm or refute findings from your ancestral studies.  Confirm possible linkages from your genealogical research and add branches to your family tree.
• Use your markers to search the Genebase database to find other Users from around the world who share the same mtDNA markers as yourself.

The more regions of your mtDNA that you test, the more precise the results of your comparison will be.  Your mtDNA contains several regions, namely, the HVR1, HVR2 and coding regions.  In the further blogs in this series, we will discuss the different types of mtDNA tests, and talk about which regions are examined by each test type. 

2.  Haplogroup Determination: 

The unique set of mutations that you carry in your mtDNA allows you to track your “deep ancestry’, ie. your ancestry from tens of thousands of years ago and discover your haplogroup. 

SNP Mutations are small “mistakes” that occur naturally in your DNA.  SNP mutations are rare, occuring at a rate of approximately one mutation every few hundred generations.  However, once a mutation occurs, it acts as a “time-and-date-stamp”, because it is passed on to all future generations.  Each mutation event can be linked to a time and place in history, and by testing the mutations in your mtDNA, you can retrace the history of your ancient ancestors. 

Let’s take a look at how mutations can allow us to trace the path of our ancestors using the following hypothetical example:

As you can see from this diagram, whenever a new ”marker” occurs, it is passed down to all future generations.  By studying all of the markers that an individual carries, we can tell them the story behind each marker, ie when did that marker first occur, and where did it occur.  By knowing when and where each marker in your mtDNA occrred, we can trace the journey of your ancestors back in time. 

In Part VII, we will begin examining some actual case studies using real mutations to see how DNA mutations are used to trace ancestry.  However, in order to understand the mtDNA mutations in the examples, you will need to have a basic understanding of the “Cambridge Reference Sequence”.  In the next blog, we will go over the Cambridge Reference Sequence and the fundamental role that it plays in mtDNA markers.