Question: What do you actually mean when saying you 'sequence' DNA? :)

Lilian Hunt answered on 11 Mar 2014:

Oooh good question. Well DNA is made up of a long backbone with 4 different molecules attached to it in a chain. These 4 molecules are called bases and are either Adenine (A), Guanine (G), Thymine (T) or Cytosine (C). There are 2 strands to DNA running in opposite directions to one another but linked through these bases. So when we sequence DNA we are getting a read out of what order these bases are joined up in a chain e.g AATCGGCAACTG.

The actual sequencing method itself varies depending how big the bit of DNA you’re sequencing is but it relies on quite expensive machines and can take a few days to complete but it is getting faster and cheaper as the technology develops. There are also lots of different companies developing different methods. Most relie on ‘tagging’ the different bases somehow so when the DNA is run through the machine, it can detect which base comes in which order by a colour or chemical type signal. Then the machine turns it into a computer file that we can use to line up all the bits of sequences it has recorded and we have our DNA sequenced 🙂