What is DNA?

Famous DNA double helix

Famous DNA double helix

We see the DNA helix everywhere. It helps market computers, trucks, and cosmetics. People use the helix as an explanation (‘in my DNA’). But do people understand this famous molecule?

In different classrooms, I have asked, “If I left DNA from a wolf in a test tube alone in a classroom, what would you do?” Some students respond, ‘drink it, so I can get wolf power’. Other students have said, ‘enter the room carefully in case the wolf is angry’. But in reality, we would just come back to DNA.

DNA is not magical. I think it is awesome but it is just a molecule. So what is it?

The full name of DNA is Dexoxyribonucleic acid. Its main function is the storage of information. It is often compared to a recipe and I like that description. If we left a recipe on the kitchen counter for chocolate cake, we wouldn’t expect a chocolate cake to appear (I’ve tried – it doesn’t work). Just like leaving wolf DNA on the counter won’t leave a wolf in the classroom. Recipes need people, ingredients, and machines to make cakes and DNA needs other things in the cell to be ‘read’.

There are 4 bases (or letters) in DNA: A, C, T, G. The order of these bases are the stored information. All living things have DNA with the same structure and bases but the order can change, leading to different things made by cells. Different organisms (humans, wolves, bacteria) use the same storage system but the instructions can be different. Another way to think of DNA is that it is  ‘the code of life on earth’ (thanks @davidmanly). But remember, DNA is just the information on how to make things and won’t spontaneously create life.

Where is DNA found?

In humans, most of our DNA is found in a protected part of the cell, called the nucleus 1. In all our cells with a nucleus, we have DNA 2. Why do we care where DNA lives? Many reasons but I’ll focus on forensics here. Every cell carries the same DNA information [think about that for a minute... our eye cells carry the same DNA as our heart cells = amazing!]

DNA is same in heart and eye cells

DNA is same in heart and eye cells

Because our DNA is the same across our cells, that means you can use a DNA sample from blood and it will match DNA from other cells = skin cells from a fingerprint, sperm cells, or cells in saliva. Note: this is also important in medicine because if you can get the same DNA information from a simple blood test.

What does DNA look like?

I’ve been showing the DNA helix that we see all over the place in this post but DNA doesn’t always look like that. In fact, I’ve never seen this structure except in drawings or models. Some ways that I’ve seen DNA:

If you decide to do a DNA extraction, you will should see the last image. Unfortunately, you need microscopes to see individual strands of DNA (second and third images) and the famous image is rarely seen.

Inheritance

One of the other cool things about DNA is that we get half from our mom and half from our dad. Humans have 23 pairs of chromosomes (long strings of DNA) and we get one of each chromosome from each parent. In other words, one chromosome 1 from dad and one chromosome 1 from mom plus one chromosome 2 from dad and one chromosome 2 from mom…see where this is going? So that means we are a mixture of information from both parents. A great visual representation from @olviakoski on twitter:

Strips combining for grid

Hee Hee :)
Source

Updated August 16, 2012:

  1. Changed the intro, adding the first paragraph. The post was originally written for a grade 7 classroom (thanks @brittgow) and the wolf DNA reference was for them.

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  1. There is some DNA in the mitochondria but we’ll save that for another day.
  2. Our red blood cells are anucleate (no nucleus) so they don’t carry nuclear DNA. DNA samples from blood are from other cells in the blood (e.g. white blood cells).

Comments

    • genegeek says

      I went to university in Canada. I first went to school for my BSc (4 years) then my PhD (5.5 years). After that, I went to England and California for a postdoc, like an apprenticeship (another 2 years). It was a long time but I would say I become a DNA scientist after the first 2 years, part way through my BSc.

  1. Tate says

    Thank you Catherine i learnt a lot. and i have a quiestion where do you have to go to be a forensic scientist.

    • genegeek says

      You can become a forensic scientist at different parts of university. Sadly, the people who are DNA experts don’t get to go to the crime scenes like they show on TV. (I forgot to tell you that!) In fact, the DNA scientists often don’t even know what cases they are working on!

  2. Kirsty says

    I learnt that you can get DNA from any part in the body except for your red blood cells and you get half of your genes from your mum and half from your dad. Thank you Catherine for talking to us on skype for Science week it was very interesting.

  3. Toby says

    how cool is DNA these days it leads back to the right person in a mystery and being a scientist and all you would have an advantage with all those things.

  4. says

    thanks for spending the time with us.
    it was strange that DNA can come from hair and bones and that TV shows are useless.

  5. says

    i learnt that you get half your DNA from your dad and half from your mum.
    thankyou for talking to us about dna

  6. Rachael says

    I never really knew much about DNA but now I know lots more. DNA is very interesting! I didn’t know that half of your DNA is from your Dad and the other half is from your Mum.
    Thank-you for teaching us about DNA!

  7. says

    Wow there is heaps about DNA. I learnt that DNA works in different ways and you can do alot with it like determining who’s finger print was most likely on a gun. And how if you touch that gun, it will be contaminated with your DNA.

    Thank you for teaching us about DNA!!!! :)

  8. Liam says

    Thanks for talking to us about DNA for Science Week. I learnt that DNA is everywhere in your body,m except in the RBC. I watch Bones and now I know it’s not alwyas how real scientists work. I don’t loook like either one of my parents, but they have given me half my genes each!

  9. Aimee says

    I learnt that all we all are nearly the same. You can not get DNA from your red blood cells but you can anywhere else. You get have of your dad’s jeans and half of your mum’s jeans. I love this photo of the mum and dad and their child. Thankyou for talking to us over skype and taking your time to talk to us year sevens. It was very interesting. Thank you.

  10. says

    Hi gene geek i thought the session was interesting and i really think dna is cool. it is cool how half of yore dna is mums and the other half is you’re dad.

  11. Anna says

    Hello Gene Geek, Thank you for teaching us about DNA, I learnt a lot and so did all of the class. Anna

  12. Molly Smith says

    I learnt what DNA stands for and what DNA can be used for.
    Thankyou for talking to us about DNA and telling us where it is in our body.

  13. says

    Thank you gene geek for teaching us about dna. I learnt that dna is in your blood and that 99.8% of your dna is the same as another persons dna. And that if you went to kill someone with a knife you should wear leather over your hands.

  14. says

    I learnt that you get half your DNA from your Mum and half from your Dad and that DNA is a recipe for protein or how you look. I already knew that from where ever in your body (except for you red blood cells) you get the DNA its always the same. Thank you for taking the time to talk to us about DNA!!! :D

  15. says

    Thanks genegeek . How did you become a dna scinetst was it hard to become a dna scintest and how long did it take to become a dna scintest

  16. Amy says

    Thank you Gene Geek for talking to as about DNA now i now that all the TV shows like CSI are not completely correct .
    from amy

  17. says

    Hello ,
    Your blog carrys a lot of infomation.
    What I learnt that red blood cells don’t work for DNA only white blood cells.
    and I also learnt that not everything on bones and other episodes like that aren’t correct with there DNA searches.
    By Emily

    • genegeek says

      I’m sorry but I don’t understand the question. Everyone’s DNA has the same structure but the order of the information (bases of A, T, C, G) can be different, leading to different products.

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