2. DNA –Was known as 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

3. DNA and RNA are nucleic acids DNA and RNA: Polymers of Nucleotides –They consist of chemical units called nucleotides –The nucleotides are joined by a sugar-phosphate backbone

4. Figure 10.2 Phosphate group Nitrogenous base Sugar Nucleotide Polynucleotide Sugar-phosphate backbone Nitrogenous base (A,G,C, or T) Thymine (T) Phosphate group Sugar (deoxyribose) DNA nucleotide

5. The four nucleotides found in DNA –Differ in their nitrogenous bases –Are thymine (T), cytosine (C), adenine (A), and guanine (G) RNA has uracil (U) in place of thymine

6. James Watson and Francis Crick determined that DNA is a double helix Watson and Crick’s Discovery of the Double Helix Figure 10.3a (a) James Watson and Francis Crick

7. Watson and Crick used X-ray crystallography data to reveal the basic shape of DNA –Rosalind Franklin collected the X-ray crystallography data Figure 10.3b (b) Rosalind Franklin

8. The model of DNA is like a rope ladder twisted into a spiral Figure 10.4 Twist

9. Detailed representations of DNA –Notice that the bases pair in a complementary fashion Figure 10.5 Hydrogen bond (a)(b) (c)

10. Structure of DNA Contains a 5-carbon sugar called deoxyribose – hence deoxyribonucleic acid Contains a phosphate group Contains 4 kinds of nitrogenous bases: Purines – adenine ( A); guanine ( G) Pyrimidines – cytosine (C); thymine (T)

12. Each DNA molecule is made up of units called nucleotides – made up of a phosphate group, a sugar and a base

13. It consists of two strands wound around each other like a twisted ladder – called a double helix The sides of the ladder are alternating units of deoxyribose and phosphate The rungs of the ladder are the 4 bases which are always bonded together in the following sequence: A-T and G-C The bases are held together with weak hydrogen bonds – two between A-T and 3 between G-C

16. DNA can make an exact copy of itself – called replication DNA is responsible for the manufacture of all proteins through the processes of transcription and translation. DNA controls all cellular functions DNA manufactures another nucleic acid called RNA

17. DNA – Why 5’ and 3’ ends? Sides of the DNA ladder made up of alternating deoxyribose sugars and phosphate groups The deoxyribose sugar’s carbons are numbers 1-5. #1 – always attached to the nitrogenous bases. #3 – always attached to the phosphate group coming into the deoxyribose sugar #5 – always attached to the phosphate group exiting the deoxyribose sugar.

18. TASK 1. Draw a DNA nucleotide. Label the phosphate group, deoxyribose sugar, & nitrogenous base 2. Define: antiparallel & complementary base pairing 3. Page 216 #2 and #5 (give 2 examples for #5)

21. 2. Despite the fact that purine is opposite to a pyrimidine, this base pairing cannot occur because the pairing does not allow for hydrogen bonding.