1. Chromosomes and DNA replication

2. Procaryotes : DNA is in the cytoplasm, circular Chromosome E. Coli Bacterium Bases on the Chromosomes

3. Eucaryotes DNA has 1000 X the base pairs as bacteria. Located in the cell nucleus, on chromosomes Folds into a space 1/1000 th of its length by wrapping around the protein histone.

4. –Eukaryotic Chromosome Structure Chromosome Su me DNA Coils Nucleosome: DNA wrapped around a histone

5. DNA replication DNA molecule separates Each side acts as a template to make a complimentary new strand. 1 molecule becomes 2

6. DNA replication cont’d Enzymes “unzip” the molecule and it uncoils. New N bases come in and bond to each side. Polymerase joins them into a new molecule. It also “proofreads” the new strands for errors.

7. DNA Replication Nitrogen Bases Replication Fork DNA Polymerase Replication Fork Original strand New Strand

8. Summary One DNA strand becomes 2 identical strands, following the rules of base pairing. Occurs at hundreds of sites along the chromosome at the same time.