2. 3.3.1 DNA Structure DNA is a polymer of Nucleotides 1.Sugar (5C) 2.Phosphate Group (C-5) 3.Nitrogenous Base (C-1) Phosphate Pentose Sugar Nitrogenous Base H Ribose (RNA) Deoxyribose (DNA) 2 alternatives 1.Adenine (A) 2.Guanine (G) 3.Cytosine (C) 4.Thymine (T) 5.Uracil (U)

3. Phosphate Pentose Sugar Nitrogenous Base 1.Adenine (A) 2.Guanine (G) 3.Cytosine (C) 4.Thymine (T) 5.Uracil (U) DNA RNA 3.3.2 DNA Structure: Nitrogenous Bases

4. The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. The nucleotides within each strand are joined by covalent bonds. Alternating sugar and phosphate molecules form a backbone for each strand. rungs backbone 3.3.3 DNA Structure

5. The two strands are held together by hydrogen bonds between the nitrogenous bases. 3.3.4 DNA Structure Each Nitrogenous base will only bond with one other specific base. Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

6. 3.3.5 DNA Structure What is DNA? Journey into DNA