2. How Is DNA Structured?

3. DNA is shaped like a twisted ladder, or double helix.

4. Genetic information is stored in the ‘rungs’ of the ‘ladder’.

5. Each rung is made of two nitrogenous bases that are paired together. Nitrogenous Base Nitrogenous Base Pair

6. But how are the ‘rungs’ joined together?

7. The nitrogenous bases are joined together by hydrogen bonds (circled in red).

8. The nitrogenous bases are named: Adenine, Cytosine, Guanine, and Thymine

9. Like most things, not all nitrogenous bases pair successfully with one another. Worst. Date. EVER.

10. Instead, nitrogenous bases are paired together in specific ways.

11. Thymine and adenine pair with each other. Cytosine and g uanine pair with each other.

12. Having trouble remembering that? These guys can help!

13. T im A llen: T hymine and A denine G eorge C looney: G uanine and C ytosine Tim Allen George Clooney

14. Or a more scientific explanation…

15. Adenine and Guanine are Purines (and pair with pyrimidines) Cytosine and Thymine are Pyrimidines (and pair with purines) Note: 2-ring structure Note: 1-ring structure

16. Handrails are important, too! (especially in the structure of DNA)

17. The ‘handrails’ of the DNA structure are sugar-phosphate backbones.

18. These backbones consist of alternating deoxyribose sugar and phosphate molecules. Note how the nitrogenous bases (G, C, T, A) are covalently bonded to the sugar in the backbones.

19. These three parts: 1. deoxyribose 2. nitrogenous base 3. phosphate group … together form a structural unit of DNA called a nucleotide.

20. The sugar-phosphate backbones travel in opposite directions. 3’ 5’

21. Collectively, these are the basic structural components of DNA.

22. Nitrogenous Base Hydrogen Bond Sugar-Phosphate Backbones Nitrogenous Base Pair Covalent Bond

23. The End

24. Image Citations Slide 1: http://lifesciencewithfranklin.blogspot.com/ Slides 2,3,4,16,20,21: http://www.sciencemuseum.org.uk/on- line/lifecycle/135.asp Slide 5: http://www.cartoonstock.com/directory/c/customer_returns.asp Slides 6,7: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mboc4&part=A2&re ndertype=figure&id=A8 Slide 8: http://www.ew.com/ew/article/0,,733023,00.html Slide 9: http://www.sciencewithmrmilstid.com/2009/02/03/ Slide 10: http://ieeexplore.ieee.org/images/ts2_sect1_02.jpg Slides 11,12,22: http://spotlightmediaproductions.biz/spotlight/getting- older-is-better-than-being-dead-george-clooney-on-career-and-aging/ and http://pageslap.files.wordpress.com/2009/05/tim-toolman-taylor.jpg Slide 14: http://www.microbelibrary.org/ASMOnly/Details.asp?ID=432 Slide 15: http://www.skarbakka.com/portfolios/struggle.htm Slides 17,18,19: http://nobelprize.org/educational_games/medicine/dna_double_helix/rea dmore.html http://lifesciencewithfranklin.blogspot.com/ http://www.sciencemuseum.org.uk/on- line/lifecycle/135.asp http://www.cartoonstock.com/directory/c/customer_returns.asp http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mboc4&part=A2&re ndertype=figure&id=A8 http://www.ew.com/ew/article/0,,733023,00.html http://www.sciencewithmrmilstid.com/2009/02/03/ http://ieeexplore.ieee.org/images/ts2_sect1_02.jpg http://spotlightmediaproductions.biz/spotlight/getting- older-is-better-than-being-dead-george-clooney-on-career-and-aging/ http://pageslap.files.wordpress.com/2009/05/tim-toolman-taylor.jpghttp://www.microbelibrary.org/ASMOnly/Details.asp?ID=432 http://www.skarbakka.com/portfolios/struggle.htm http://nobelprize.org/educational_games/medicine/dna_double_helix/rea dmore.html