WHAT IS WHOLE GENOME SEQUENCING?
The concept of whole genome sequencing may be new to you. Whole genome sequencing tests all 3 billion base pairs of your DNA and can provide more comprehensive information over other genetic tests which only test single genes or a handful of genes.
Whole genome sequencing involves taking a sample of your cells, in this case we use saliva, and testing it for changes or variations from a 'normal'' gene. Variations in genes are also known as genetic mutations and these can signify whether a person has a certain condition or disease, or the person has a likelihood of developing or passing on a condition or disease with a genetic basis.
Whole genome sequencing allows you to understand your risks for breast cancer and other cancers you may be concerned about.
Our genome can be thought of as our DNA encyclopedia. The information in our genome encyclopedia is organized into about 21,000 gene chapters which are located within 23 chromosome volumes. Each individual has two nearly identical copies of each chromosome volume, one copy from each parent.
All of the entries in our genome encyclopedia are written in a special language-the DNA code. The DNA alphabet has only four letters, A, C, T, and G, representing the four different chemical bases. In total, each person has more than three billion DNA letters in their 23 pairs of chromosomes.
Whole genome sequencing allows us to read almost all of the more than three billion letters in our DNA sequence, determine their order, and detect subtle DNA changes, or typos, at almost every position. When the DNA letters change, it can alter the words within a gene and sometimes the instructions they provide.
To sequence the whole genome, the entire genome encyclopedia is broken into smaller fragments of about 200-300 DNA letters each. Since humans are very similar, a reference human genome sequence can be used to help line the fragments up in the correct order. To make sure each individual DNA letter has been read correctly, each fragment is read many, many times.
Source: Illumina Genomics 101