This tutorial is Part 1 of a 10 part series.
Part 1, What is mtDNA? <<== You are here
Part 2, Facts about mtDNA
Part 3, Structure of mtDNA
Part 4, Ancestral Markers in mtDNA
Part 5, Detecting Markers in mtDNA
Part 6, Tracing Ancestry with mtDNA
Part 7, The Cambridge Reference Sequence
Part 8, mtDNA Test Types
Part 9, mtDNA Haplogroup Determination
Part 10, mtDNA Subclades
This tutorial provides an in depth lesson about mtDNA and how it allows us to trace our maternal ancestry. The lessons start off with the basics, such as “what is mtDNA” and then advances to in depth case studies involving mtDNA. In order to fully understand the power of mtDNA testing and its applications in ancestry, it is beneficial to understand the science behind the technology and have a good idea of how ancestry testing works, including understanding its strengths and limitations. This tutorial consists of a number of lessons that will dissect the mtDNA, allowing you to learn the details of mtDNA markers and hopefully giving you a full technical understanding of how mtDNA ancestral tests work.
You don’t need to understand how mtDNA testing works in order to understand your results, but the more you know about “how”, “why” and “what’s next” when it comes to mtDNA testing, the more you will get out of your mtDNA ancestry testing experience.
mtDNA stands for “mitochondrial” DNA. All of us, both males and females, carry mtDNA. mtDNA is found in most of the cells in our body.
mtDNA is unique because while most of the DNA in our body is found in the nucleus of our cells, mtDNA is found in small structures or organelles called “mitochondria”. Mitochondria is found in the cytoplasm of our cells, NOT in the nucleus (remember this, because it’s important when we discuss how mtDNA is inherited).
Mitochondria is important for producing energy “ATP” for our cells.
Many copies of mtDNA are found in every mitochondria and many mitochondria are present in the cytoplasm of each cell. That means that we have many more copies of mtDNA in our cells than other types of DNA which are present in only one set per cell. The huge abundance of mtDNA as well as its small size makes it an excellent candidate for forensic studies of old or degraded samples. Many archaeological studies of ancient DNA samples which are hundreds of years old rely on mtDNA testing.
Where do we get our mtDNA?
Our mtDNA comes from our mother, and our mother got her mtDNA from her mother, and so on. The reason for the maternal inheritance pattern of mtDNA is due to its localization in the cytoplasm. When an egg is fertilized, the cells of the resulting embryo contain the cytoplasm of the egg, not the sperm. Since mtDNA is found only in the cytoplasm, all of our mtDNA comes from our mother, not our father. As the embryo continues to develop into a full grown human, all of the cells in the resulting human contain strictly the cytoplasm and mtDNA of the mother.
Maternal inheritance pattern of mtDNA:
mtDNA has a very unique inheritance pattern which differs from all the other types of DNA in our body. It is passed down strictly along the maternal line from a mother to all of her children. Males will carry the mtDNA of their mother, but when they have children, their children will carry the mtDNA of their own mother, not their father. Thus, only daughters will pass the mtDNA on to future generations.
Why does mtDNA hold ancestral information?
The maternal inheritance pattern of the mtDNA has important significance for ancestral studies. While most of the other types of DNA in our body become mixed as they are passed down from generation to generation, the mtDNA remains unmixed because it has a strict single line of descent from mother to child. This means that our mtDNA is the same as our mother’s and our mother’s mother’s mtDNA from hundreds, even thousands of generations ago. By testing our own mtDNA, we are able to indirectly read the mtDNA genetic code of our own maternal ancestors from thousands of generations ago. In summary, mtDNA testing will allow us to trace our direct maternal lineage (mother's mother's mother's..... maternal lineage).
This is a brief overview of mtDNA.
Next, we will discuss important facts about mtDNA >>