1. DNA Deoxyribonucleic acid

2. DNA structure DNA is a nucleic acid –composed of many nucleotides –A nucleotide is composed of a sugar (deoxyribose), a phosphate group, and a base –Bases are Adenine (A), Thymine (T), Cytosine (C), and Guanine (G)

4. More DNA Structure DNA molecule is two strands of nucleotides which are twisted around each other Held together in the middle by hydrogen bonds shape is a double helix—looks like a twisted ladder

5. Alternating sugars and phosphates form the sides of the ladder (“DNA Backbone”) Bases (A, T, C, and G) form the “rungs” of the ladder

7. Just a little more DNA structure… The two sides of the DNA molecule are complementary –A always pairs with T –C always pairs with G

8. Practice Problems Write the complementary strand for A-C-C-T-G-A-C-T-G Write the complementary strand for C-G-G-G-C-A-T-T-A

9. More Practice Problems Write the complementary strand for T-C-G-G-T-T-A-T-C Write the complementary strand for C-G-C-T-A-T-C-C-A

10. Check Your Understanding What are the building blocks of a DNA molecule? What are the parts of a nucleotide? What are the bases in DNA? What holds a DNA molecule together in the middle? What term describes the shape of a DNA molecule? What forms the DNA backbone? What forms the rungs of the DNA ladder? Write the complementary strand for C – A – T – T – G – C – A