1. DNA contains the genetic instructions that determine traits and is found in the cells of living organisms. 2. DNA is made up of nucleotides, which consist of phosphate, sugar, and one of four nitrogenous bases (adenine, guanine, cytosine, thymine). 3. Watson and Crick discovered that DNA takes the shape of a double helix with the bases on the inside pairing up in specific ways (A pairs with T, C pairs with G) to form the rungs of the ladder-like structure.

1. WARM-UP #7

2. DNA (Deoxyribonucleic Acid)

4. DNA Nucleotide O O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) CH2 O C 1 C 4 C 3 C 2 5 Sugar (deoxyribose)

7. DNA Double Helix Nitrogenous Base (A,T,G or C) “ Rungs of ladder” “ Legs of ladder” Phosphate & Sugar Backbone

8. DNA Double Helix P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C T A

11. BASE-PAIRINGS C G H-bonds T A

14. DNA is wrapped tightly around histones and coiled tightly to form chromosomes See p. 297