1. Animations/websites http://www.wiley.com/college/pratt/0471393 878/student/animations/dna_replication/inde x.html http://www.wiley.com/college/pratt/0471393 878/student/animations/dna_replication/inde x.html http://www.nobelprize.org/educational/medi cine/dna_double_helix/ http://www.nobelprize.org/educational/medi cine/dna_double_helix/

2. DNA replication

3. DNA length DNA molecules are very long – Example: E. coli bacteria- 4,639,221 base pairs In order to fit in side of the nucleus of a cell the DNA must be folded very small A human cell contain 100 times the b.p. found in bacteria (3.2 billion b.p.)

4. Chromosome Structure The nucleus of a cell contains more then 1 meter of DNA What is a chromosome made up of? Review! Chromosomes contain both DNA and protein Protein= histones

5. Chromosome Structure DNA + Histone protein= Nucleosome Nucleosomes pack together to further condense

7. Location of Replication Where is DNA stored in the cell? Can DNA leave the nucleus? (why?) – DNA replication takes place inside of the Nucleus Why does DNA need to Replicate? When does DNA replicate? – Replication takes place before cell division

8. DNA Replication DNA is copied to make 2 identical DNA strands Each strand of the original double-stranded DNA molecule serves as template for the production (semi-conservative)

9. How it works DNA replication is carried out by a series of Enzymes

10. Steps to replication Step 1 1.The DNA molecule is unwound and prepared for synthesis by helicase (replication fork) Helicase- separates DNA strand

12. Step 2- Single- stranded Binding proteins 2.Single-stranded binding proteins (SSB)- keeps strands apart during replication

13. 3. Elongation- different for each side of the DNA strand Steps to replication

14. DNA directionality Review! The strands are oriented in opposite directions. This is the only way the bases can line up to form the hydrogen bonds

15. 5’  3’ 5’  3’ refers to the order of the carbons in the deoxyribose sugar

16. 5’  3’ strand Step 3 A Called the leading strand RNA primase adds primer DNA polymerase can “read” the template – continuously add nucleotides (into fork) Nucleotides are added according to the base pairing rule

17. DNA Polymerase DNA polymerase moves along the template strand in a 3'-5' direction – daughter strand is formed in a 5'-3' direction. Nucleotides are added according to the base pairing rule

18. 3’ to 5’ strand Step 3B The new strand is called the lagging strand Cannot be read by DNA polymerase (oriented in the opposite direction) Replication takes place AWAY from fork

19. Lagging Strand 1.RNA Primase reads the sequence and adds primer 2.DNA polymerase lengthens the segment – Formation of Okazaki fragments 3.Helicase unzips more of the strand

20. Okazaki fragment

21. Lagging Strand DNA ligase connects the fragments together

23. DNA polymerase proofreads as it adds nucleotides

24. “Key players” DNA polymerase- adds new nucleotides RNA primase- starts replication on upside down strand DNA ligase- connects new fragments on upside down strand