Maternal DNA Introduction
Scientific research over the last fifteen years has gradually clarified the genetic relationships between all the peoples of the world, showing that we are all part of the same evolutionary tree - we are all human!
The maternal family tree assigns your mitochondrial DNA analysis result to one of 36 clans, each founded by one woman, whose names appear on the MatriLineTM World Clans certificate. The clusters of mitochondrial DNA sequences are shown as circles and their relationship to one another indicated by the connecting lines.
The certificate shows a read-out of the mitochondrial DNA sequence and, above it, a chart of human evolution with the place in the scheme marked by a star.
The DNA sequence consists of a long series of four different letters: A, C, G, and T. These letters are shorthand for the four different chemicals that are strung together to make the long chain we know as DNA. The exact order in which these letters occur is a code that tells our cells how to divide, how to grow into a human and how to perform the many different tasks required of them.
We have only read a small part of the DNA, four hundred letters to be exact. The total length of the DNA message is much, much longer; about 3,000 million letters longer, in fact, and these billions of letters are what make up the genome.
The Mitochondrial DNA
DNA is passed on to the next generation in sperm and eggs. Mitochondrial DNA (mtDNA, for short) is special because it is only passed on through the egg. This means that everyone has inherited their mtDNA from their mother. She inherited it from her mother, who inherited it from her mother, who inherited it from hers - and so on back through time. Therefore, mtDNA provides a direct link to our maternal ancestors. We all inherit other genes from many other ancestors, but only mtDNA traces a direct maternal line.
The DNA sequence that has been passed on to you with little or no change from your remote female ancestors. Think of it as a very long word with four hundred letters. To compare the distinct spellings that we find in different people, we use what we call a reference sequence, actually the most frequent sequence found in Europe. Where your sequence differs from the reference 'spelling', we have picked-out the letters in red. If there are no red letters, then your mtDNA sequence is identical to the reference sequence.
DNA Change Over Time
When cells divide, the DNA that they contain has to be copied. Fortunately, this is an extremely accurate process and mistakes occur only very rarely. When they do, however, they are called mutations. If they happen in a gene responsible for an important cell function, then they can give rise to severe inherited diseases, like cystic fibrosis or muscular dystrophy. However, the great majority of mutations occur without having any obvious effect at all. Mutations in the section of mtDNA that we sequenced are of no consequence to your health, but they are extremely useful for studying our ancestry. This is because, on average, one mutation occurs in mtDNA every twenty thousand years!
Interpretation of the World Clan Certificate
The chart on my certificate is made up of interconnecting circles. Each of these circles represents a group of related DNA sequences and their colors indicate the geographical distribution of the modern day descendants of the clan. The details of the chart have been worked out in Oxford using over 18,000 mtDNA sequences from people living all over the world. The lines connecting the circles trace the evolutionary pathways of our ancestors. Each line connects two circles whose sequences differ by one or more changes (mutations) out of the 400 DNA letters that we read. The grey star, or node, near the bottom-left of the chart represents the sequence of the ancestral mother through whom we are all related, the woman known as "Mitochondrial Eve". It is through her that we are related to the other, now extinct, species of humans, Homo erectus and Homo neanderthalensis, shown on the chart as a dashed line. The other grey nodes on the chart represent DNA sequences that we have not yet found in any person living today, but that we know from our reconstructions must have existed.
Interpretation of the Seven Daughters of Eve Certificate
If you trace your maternal ancestry to Europe and are one of the 95% whose mitochondrial DNA sequence is found in one of the "Seven" major European clans, then you will have received one of our "Seven Daughters of Eve" certificates. The interconnecting circles on this certificate are of different sizes, reflecting the approximate number of people in Europe who have that particular sequence. The largest of the grey circles near the top-centre of the chart represents the sequence that connects the Seven Daughters of Eve chart to the rest of the world, through the dashed line.
The star shows the chart position of your own sequence. It belongs to one of the 36 groups or clans that have been identified to date, each of which is shown by a colored circle. The members of each clan are all descended from a single female ancestor through the direct maternal line traced on the chart. We call these women clan mothers and from your DNA sequence we are able to tell to which clan you belong and which of these 36 women is your maternal ancestor.