Genome sequencing – procedure

Your genome is a unique double strand of DNA and the genome contains more than 3 billion pairs of letters (see genome testing). The genome is found in almost every single cell in your body.

Collecting DNA
In order to carry out your genome test, you will have to provide a tissue sample. This is usually done by drawing blood. DNA is then extracted from the blood sample.

There are several different methods and different types of equipment that can be used to sequence a genome. Sequencing machines cannot read the entire genome at the same time. In stead, small fragments of about 150 letters are read in batches. Each fragment is known as a read.

The reads from the sequencing machine are then compared to a reference genome. This is done using mapping software on high performance computers, which map where in the genome each read belongs. Once all the pieces have been put back into place, your specific genome is available in digital format.

Scientists around the globe use reference genomes. These are genomes put together using data from many people from a restricted geographical area, and can therefore be seen as representative of a specific group, i.e. an ethnic group, because they show the average genetic composition of this body of people.

The FarGen project aims to produce a Faroese reference genome.

Today the place (locus) of most of our genes is known and marked in the reference genome. Once your genome has been fully mapped, it is possible to detect the differences between your individual genome and the reference genome.  

We all have millions of mutations (variations) in comparison with the reference genome. These variations may be individual letters, a series of letters in a different place, missing letters or extra letters. Most of these mutations are completely harmless and simply make us different. Some mutations, however, can cause disease.

Experts in bioinformatics specialise in analysing genome data or other biological data. They develop methods and software that enable us to analyse and interpret data, so that the millions of genetic mutations in each individual are whittled down to a few that may be harmful. People working in this field have usually studied biology, engineering, computer science or mathematics.