1. DNA The Molecule of Life

2. DNA STRUCTURE I.Double Helix shape A.Like a twisted ladder

3. II.Nucleotide A.The basic unit of DNA; DNA is a *Nucleotides stacked together form one side of the DNA chain. The opposite side consists of more nucleotides stacked together

4. A.Nucleotides consist of three basic parts: A.(one of four: A, T, G or C) B.(makes up the “side” of the “ladder”) C.(makes up the “side” of the “ladder”)

5. Nitrogenous Bases III.Each nucleotide contains one nitrogenous base A. (A) B. (G) C. (T) D. (C) IV.Each rung of the ladder consists of two bases paired together. A. Adenine always pairs with B. Cytosine always pairs with

6. V. Bases pair this way because of their shape: A.Pyrimidine: one ring shape 1.Cytosine 2.Thymine B.Purines: two ring shape 1.Adenine 2.Guanine *If two purines bind together it is too large to fit *If two pyrimidines bind together it is too small to fit *Additionally each base has a unique chemical structure that forms hydrogen bonds with only one other base.

7. DNA Replication I.DNA denatures (falls apart) easily into two separate strands A.Bases are held together by weak

8. A.Enzymes (proteins) unwind the DNA strand B.Different enzymes pair single nucleotides to the template strand C.When the pairing is complete there are two identical strands of DNA molecules http://www.courses.fas.harvard.edu/~biotext/animations/replication1.html

9. DNA Strand….

10. Replicate the DNA Strand Pull apart the the strands match the nucleotides (copy and paste new ones, rotate to fit into place) Check for errors Label where hydrogen bonds would be Label a nucleotide Label a nitrogenous base