HOW GEOGENE DOES THE ANALYSIS

This explanation is for analysis of paternal ancestry (GeoFather™). The analysis of maternal ancestry (GeoMother™) is similar, with the exception that mitochondrial DNA is examined rather than the Y chromosome.

In order to unravel the historical roots of your DNA, GeoGene first needs a sample of your DNA. To do this, we provide you with a sample kit containing a mouth swab that allows you to collect loose cells from the inside of your mouth and transfer these to a special card, which you can then return to us in the envelope provided.

To preserve anonymity, each mouth swab sent to the testing laboratory is identified by a unique serial number rather than the person’s name.

In the testing lab at the University of London we extract your DNA from this card. This involves breaking up the cells to release tiny quantities of DNA. We separate this DNA from the rest of the cell contents, then wash it several times to ensure it contains no contaminants (such as proteins, carbohydrates or lipids) which might hinder further work. Once DNA has been isolated it is kept in tubes at -20°C.

GeoGene’s goal is to sequence a specific section of your DNA to determine what base you have at a particular position. Your genome (your complete set of genes) is extremely large: 3 billion bases grouped onto 46 chromosomes. We could sequence directly from the raw DNA but to make the process much more efficient we amplify the small region (200-400 bases) whose sequence we wish to obtain employing a technique known as ‘polymerase chain reaction’ (PCR). PCR is at the core of much molecular biological work and its inventor, Dr. Cary Mullis, received the Nobel Prize in recognition of this. PCR allows a scientist to ‘zoom in’ on a short, specific stretch of DNA and then make many copies of this region.

GeoGene takes a small quantity of your DNA and adds it to a tube containing reagents for a PCR reaction. These include small pieces of DNA called primers, and copies of the nucleotide sequences located each side of the site we are interested in, together with individual nucleotides (A, T, C and G) plus an enzyme known as taq polymerase. This mix is then loaded onto a machine where it is alternately heated and cooled 20-40 times, helping the reaction to take place and allowing multiple copies of the relevant sequence to be completed. Once the process has been completed, the tube will contain millions of copies of the stretch of DNA we are interested in.

The next step in the process is to determine the sequence of this amplified region. GeoGene does this using a technique known as automated fluorescent DNA sequencing, which uses differently coloured dyes for each of the four DNA bases, within the Sanger chain termination sequencing method. (The Sanger sequencing method was developed by another Nobel Prize winner, Fred Sanger, and is the standard today.)

GeoGene analyses your DNA sequence using computer software to identify the exact base positions that hold the key to your Y chromosome’s demographic history. By deducing what sites you are either ‘derived’ or ‘ancestral’ for, we can identify how you fit into the phylogenetic tree of worldwide Homo sapiens Y chromosomes.

Both the GeoFather™ and GeoMother™ services take between 4 and 8 weeks to complete. The longer time period may be necessary if tests need to be rerun. We will inform you if there is any delay.