1. Review about DNA

2. What is the structure below called?

3. What are the three pieces that make up a nucleotide?
Phosphate
Nitrogen Base
Sugar

4. What kinds of bonds exists between the Bases of DNA?

5. Watson and Crick found that DNA was in the shape of an?

6. Adenine always binds with______
Cytosine always binds with_____
Thymine always binds with_____
Guanine always binds with_____

7. Chromosomes Eukaryotes Prokaryotes Found in the nucleus
DNA is found in the cytoplasm
Single circular DNA molecules
DNA replication begins at a single point in the chromosome & proceeds in both directions until the chromosome is replicated
Eukaryotes
Found in the nucleus
Chromosome number varies between species
DNA replication occurs at hundreds of places called replication forks

8. Chromosomes How much DNA in a human nucleus? What is chromatin?
more than 1 meter
What is chromatin?
DNA tightly coiled around proteins called histones

9. Chromosomes How are chromosomes constructed?
DNA & histones form beadlike structures called nucleosomes
Nucleosomes pack with one another to form thick fibers
Fibers are shortened by a system of loops & coils

10. Replication

11. Replication – General Info
The exact copying of DNA
Replication occurs in both directions
DNA must be copied before cells divide  each daughter cell has a complete set of DNA
Original strands serve as templates for new strands

12. Replication – General Info
How it happens:
Helicase (enzyme) unwinds the DNA by breaking hydrogen bonds

13. Replication – General Info
DNA polymerase (enzyme) joins individual nucleotides to each separated strand, producing DNA molecule
DNA polymerase also proofreads each new DNA strand to make perfect copies

14. Replication – General Info
Results: 2 DNA molecules  each contains one original
strand & one new strand