Question: why do you want to breake open the cells and put the enzyme in

Amelia Markey answered on 20 Jun 2011:

So my project is about copying DNA. The DNA is inside the cells so I need to break them open and get it out. Then I need to mix in an enzyme that will copy the DNA that has leaked out of the broken cell.

Copying DNA (or whole genome amplification) can be useful for many reasons most of these are when either you need a lot of DNA to do a lot of tests or when you don’t have much DNA to begin with. Here are a couple of examples:

Forensics – often samples (blood, hair etc) are taken from crime scenes and need to be tested (to find out who they belong to). Usually these samples are very small, just a blood spot or a single hair. There aren’t enough cells (or enough DNA) in this small sample to be able to test so to get more DNA to test the best thing is to copy the DNA that’s already there. The reaction can give you a huge amount of DNA even from a very small sample of your original DNA.

Preimplantation genetic diagnosis – this is used to screen embryos, made by IVF, for specific diseases before they are implanted into their mother so they will grow to be healthy babies. This is often done on single cells as you want to test at a very early stage before the fertilised egg becomes a baby. A single cell definitely doesn’t have enough DNA to be able to do all the test so this DNA is also often copied.

Richard has also mentioned in some of his previous answers that he used this technique to copy the primate DNA he uses as this sample is quite “precious”. Some samples are difficult to obtain and so can be quite small, samples can also be small for ethical reasons (it would harm a small child if you took a large sample of their blood).

Hope this answers your question 🙂