What is DNA (deoxyribonucleic Acid)?
Welcome to Quatr.us Study Guides!

What is DNA?

DNA
A strand of DNA (seen through an electron microscope)

If the RNA theory of the origin of life is right, then after a short time, about four billion years ago, the oceans on Earth had a lot of these strands of RNA molecules floating around in them, making proteins, and also making new strands of RNA. But RNA molecules were weak, and they were always breaking and making copies that were not really exactly right - not exactly the same as the original RNA molecule.

This was partly helpful, because there got to be a lot of different kinds of RNA molecules, and therefore a lot of different kinds of proteins. But it was also partly bad, because if you had a good healthy RNA molecule it was hard to copy it exactly.


Here is a video that shows how DNA zips and unzips.

Some of these RNA molecules evolved to make two sides to their spiral staircases instead of just one. These formed a double helix: two spirals twisting inside each other. It was a much more complicated kind of molecule, but it was much stronger, just as a ladder is stronger with two sides than with only one. These new molecules are called deoxyribonucleic acid, or DNA for short. DNA stairs are made of two purines - adenine and guanine - and two pyramidines - thymine and cytosine.

DNA double helix
This photo shows the edges of the double helix.

When a DNA molecule needed to make a copy of itself, it had nowhere for the new purines to fasten on to. So it had to unzip itself, just like the zipper on your jacket, and then it could make some new molecules and then zip itself back up again.

Learn by doing - DNA model building
Another project - seeing real DNA from a strawberry
The next step in the development of life: cells

Bibliography and further reading about DNA:

RNA
Cells
Biology
Chemistry
Quatr.us Home


Celebrating Black History Month with the pharaoh Hatshepsut, the queen Shanakdakhete, the poet Phillis Wheatley, the medical consultant Onesimus, the freedom fighters Toussaint L'Ouverture, Denmark Vesey, Yaa Asantewaa, and Samora Moises Machel, and the civil rights leader Martin Luther King, Jr.
Please help other teachers and students find us: link to this page from your class page.
Karen Carr is Associate Professor Emerita, Department of History, Portland State University. She holds a doctorate in Classical Art and Archaeology from the University of Michigan. Follow her on Instagram or Twitter.
Cite this page
  • Author: K.E. Carr
  • Title:
  • Site Name: Quatr.us Study Guides
  • Publisher: Quatr.us
  • Date Published:
Proud of your class page, homework page, or resource page? Send it in and win a Quatr.us "Great Page!" award!
Sign up for more free articles and special offers in Quatr.us' weekly newsletter:
We will never share your e-mail address unless you allow us to do so. View our privacy policy. Easy unsubscribe links are provided in every email.
Comment on This Article

Cool stuff we've been enjoying: Looking for birthday gifts? Check out these new Chromebooks - all the computer you need for only $229.00!. Then study in peace with these Beats wireless headphones - for the exact same price! When you're done, show off your presentation or watch a movie with this excellent smartphone projector for only $39.99!


Does your class page honor diversity, celebrate feminism, and support people of color, LBGTQ people, and people with disabilities? Let us know, and we'll send you a Diversity Banner you can proudly display!
Looking for more?
ADVERTISEMENT
Quatr.us is loading comments...
(Comments will appear after moderation, if they are kind and helpful. Feel free to ask questions, and we'll try to answer them.)
Cite this page
  • Carr, K.E. . Quatr.us Study Guides, . Web. 24 February, 2017
ADVERTISEMENT