1. © 2010 Pearson Education, Inc. DNA: STRUCTURE DNA: Deoxyribonucleic acid Was known to be a chemical in cells by the end of the nineteenth century Has the capacity to store genetic information Can be copied and passed from generation to generation

2. © 2010 Pearson Education, Inc. DNA and RNA Structure DNA and RNA are nucleic acids. They consist of chemical units called nucleotides. The nucleotides are joined by a sugar-phosphate backbone. Watch these(nucleotides) https://youtu.be/NNASRkIU5Fw https://youtu.be/NNASRkIU5Fw

3. © 2010 Pearson Education, Inc. The structure of DNA and RNA Genetic material of living organisms is either DNA or RNA. DNA – Deoxyribonucleic acid RNA – Ribonucleic acid Genes are lengths of DNA that code for particular proteins.

4. © 2010 Pearson Education, Inc. DNA and RNA are polynucleotides Both DNA and RNA are polynucleotides. They are made up of smaller molecules called nucleotides. DNA is made of two polynucleotide strands: RNA is made of a single polynucleotide strand:

5. © 2010 Pearson Education, Inc. Structure of a nucleotide A nucleotide is made of 3 components: A Pentose sugar This is a 5 carbon sugar The sugar in DNA is deoxyribose. The sugar in RNA is ribose.

6. © 2010 Pearson Education, Inc. Structure of a nucleotide A Phosphate group Phosphate groups are important because they link the sugar on one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide.

7. © 2010 Pearson Education, Inc. Structure of a nucleotide A Nitogenous base In DNA the four bases are: Thymine Adenine Cytosine Guanine In RNA the four bases are: Uracil Adenine Cytosine Guanine

8. © 2010 Pearson Education, Inc. Nitrogenous bases – Two types Pyramidines Thymine - T Cytosine - C Uracil - U Purines Adenine - A Guanine - G

9. © 2010 Pearson Education, Inc. Adenine

10. © 2010 Pearson Education, Inc. Guanine

11. © 2010 Pearson Education, Inc.

12. Sugar phosphate bonds (backbone of DNA) Nucleotides are connected to each other via the phosphate on one nucleotide and the sugar on the next nucleotide A Polynucleotide

13. © 2010 Pearson Education, Inc. Sugar-phosphate backbone Phosphate group Nitrogenous base DNA nucleotide Nucleotide Thymine (T) Sugar Polynucleotide DNA double helix Sugar (deoxyribose) Phosphate group Nitrogenous base (can be A, G, C, or T) Figure 10.1

14. © 2010 Pearson Education, Inc. Polynucleotide Phosphate group Nucleotide Sugar DNA Nitrogenous base Nitrogenous base Number of strands Sugar DNA RNA Ribose Deoxy- ribose CGATCGAT CGAUCGAU 1 2 Figure 10.UN3

15. © 2010 Pearson Education, Inc. The four nucleotides found in DNA differ in their nitrogenous bases. These bases are: Thymine (T) Cytosine (C) Adenine (A) Guanine (G) *RNA has uracil (U) in place of thymine.

16. © 2010 Pearson Education, Inc. Watson and Crick’s Discovery of the Double Helix James Watson and Francis Crick determined that DNA is a double helix.

17. © 2010 Pearson Education, Inc. The model of DNA is like a rope ladder twisted into a spiral. The ropes at the sides represent the sugar-phosphate backbones. Each wooden rung represents a pair of bases connected by hydrogen bonds.

18. © 2010 Pearson Education, Inc. Twist Figure 10.4

19. © 2010 Pearson Education, Inc. DNA bases pair in a complementary fashion: Adenine (A) pairs with thymine (T) Cytosine (C) pairs with guanine (G)

20. © 2010 Pearson Education, Inc. (c) Computer model (b) Atomic model (a) Ribbon model Hydrogen bond Figure 10.5

21. © 2010 Pearson Education, Inc. Check out the 5’ and 3’ binding sites!

22. © 2010 Pearson Education, Inc. James Watson (L) and Francis Crick (R), and the model they built of the structure of DNA

23. © 2010 Pearson Education, Inc. Base pairing The Nitrogenous Bases pair up with other bases. For example the bases of one strand of DNA base pair with the bases on the opposite strand of the DNA.

24. © 2010 Pearson Education, Inc. Double helix

25. © 2010 Pearson Education, Inc.

27. The Rule: Adenine always base pairs with Thymine (or Uracil if RNA) Cytosine always base pairs with Guanine. This is beacuse there is exactly enough room for one purine and one pyramide base between the two polynucleotide strands of DNA.

28. © 2010 Pearson Education, Inc. Complementary base pairing PurinesPyramidines Adenine Thymine AdenineUracil GuanineCytosine

29. © 2010 Pearson Education, Inc. Nature of the Genetic Material Property 1 - it must contain, in a stable form, information encoding the organism’s structure, function, development and reproduction Property 2 - it must replicate accurately so progeny cells have the same genetic makeup Property 3 - it must be capable of some variation (mutation) to permit evolution

30. © 2010 Pearson Education, Inc. Replication of DNA and Chromosomes Speed of DNA replication: 3,000 nucleotides/min in human 30,000 nucleotides/min in E.coli Accuracy of DNA replication: Very precise (1 error/1,000,000,000 nt)

31. © 2010 Pearson Education, Inc.

34. Meselson and Stahl (1958)