What is DNA sequencing?

DNA sequencing is the process of working out the exact order of the four bases in a strand of DNA.

Human chromosomes range in size from about 50,000,000 to 300,000,000 base pairs

Human chromosomes range in size from about 50,000,000 to 300,000,000 base pairs and each human being has 46 (23 pairs) of these chromosomes. This means we have approximately 3.2 billion bases of DNA in total!

At present, we can’t sequence a genome, or even a single chromosome, from start to finish. We have to break it up into smaller, more manageable chunks, or fragments. The order and number of bases in these fragments of DNA is then identified through techniques that label each base individually (in modern techniques the bases are labelled with different colours). From this information, scientists are able to work out the sequence of the DNA and find out lots of other interesting things about our genetic makeup.

We can now sequence an entire human genome in a matter of hours.

Early DNA sequencing was technically challenging and slow. Resources were expensive, and the reactions required complex conditions to work. It therefore took several years to sequence just one or two genes!

Over the last decade, DNA sequencing technologies have developed rapidly. We can now sequence an entire human genome, all 3.2 billion letters, in a matter of hours and for much less money.