• Question: How do you extract DNA from blood and hair?

    Asked by jetfire to Adam, Joanna, Louise S, Louise W, Marcus on 16 Nov 2012.
    • Photo: Marcus Wilson

      Marcus Wilson answered on 16 Nov 2012:

      its really quite simple. blood and hair themsleves dont have any DNA, but the cells associated with them do. so you can take the cells, break them open and then extract DNA mainly because it has a different chemical property to the other stuff in cells. you cabn get rid of proteins and fats and then precipitate DNA using alcohol. http://www.youtube.com/watch?v=vPGKv53zSRQ

    • Photo: Joanna Giles

      Joanna Giles answered on 16 Nov 2012:

      Red blood cells don’t have nuceli and so don’t have DNA, but White blood cells have a nucelus and soo have DNA! I purify the DNA from white blood cells almost every day.
      You can burst open cells with detergents that disrupt the cell membrane and release all the contents into the solution (called a lysate). Then you can spin out the big stuff really fast in a centrifuge and get rid of it. These days you can get kits that allow you to purify DNA in less than an hour. A lot of these kits have little tubes in that bind specifically to the DNA when you put your solution in (so the DNA sticks to the tube) and then you can release the DNA from the tubes by adding water. You are then left with your DNA dissolved in water – and it’s very stable too. A bonus!

    • Photo: Louise Walkin

      Louise Walkin answered on 18 Nov 2012:

      Yes, the cells associated with hair have DNA that’s how forensics work out the DNA of the person who left a strand of hair behind at a crime scene!
      White blood cells have DNA but red cells do not as they don’t have a nucleus to store the DNA. The cell membrane needs to be disrupted to access the nucleas, but then the nucleus has a membrane surrounding it as well so that also needs to be broken down. All of the cell contents are then released and you then use a special procedure to extract the DNA from all the cells contents that are mixed together. The kits for this procedure are very simple to use and allow you to collect DNA that you can then analyse! 🙂

    • Photo: Adam Paige

      Adam Paige answered on 19 Nov 2012:

      You can use the same principles as described by the others to extract DNA using simple things you can find at home. There are some good protocols on the internet for extracting DNA from strawberries for example using detergent and rubbing alcohol that you can buy in the supermarket or at a chemist.

      See http://genetics.thetech.org/online-exhibits/do-it-yourself-strawberry-dna
      It is a lot of fun. My children got to have a go at a science fair we were at last year, and they loved it.

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