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DNA Replication. Facts: DNA replicates before a cell divides Occurs during the S or synthesis phase of mitosis Replication creates identical copies of.

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Presentation on theme: "DNA Replication. Facts: DNA replicates before a cell divides Occurs during the S or synthesis phase of mitosis Replication creates identical copies of."— Presentation transcript:

1 DNA Replication

2 Facts: DNA replicates before a cell divides Occurs during the S or synthesis phase of mitosis Replication creates identical copies of DNA strands Takes place in the nucleus

3 3 Nitrogenous Base (A,T,G or C) Rungs of ladder Legs of ladder Phosphate & Sugar Backbone DNA Double Helix

4 Replication: Begins at Origin of Replication Begins at Origin of Replication Two strands open forming a Replication Forks (Y-shaped region) Two strands open forming a Replication Forks (Y-shaped region) New strands grow at the forks New strands grow at the forks ReplicationFork Parental DNA Molecule

5 Enzymes The Enzyme, Helicase, unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds The Enzyme, Helicase, unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds DNA polymerase adds nucleotides complimentary to the parental strand DNA polymerase adds nucleotides complimentary to the parental strand

6

7 Mutations What do you think a mutation is?

8 Proofreading - Replication occurs at multiple sites along the DNA - DNA polymerase is very accurate - However mutations do occur - Proofreading occurs continuously by DNA polymerase

9 More practice Write the complimentary strand: T A C G G A C T A A C G C

10 More practice Write the complimentary strand: T A C G G A C T A A C G C A T G C C T G A T T G C G

11 Review: If there is 20% Thymine bases on a DNA strand what are the percentages of the other three bases?

12 Answer: 20% Thymine = 20% Adenine 20% + 20% = 40 % 100% - 40% = 60% 60% / 2 = 30% 30% Cytosine and 30% Guanine

13 Review When and where does DNA replication occur? What is the relationship between adenine and thymine called? What are the two enzymes involved in DNA replication?

14 Activity In pairs you are going to create your own DNA models.

15 Pieces Sugar - Black pentagon Phosphate - White tube Nitrogenous bases - – Adenine - Orange (5) – Guanine - Yellow (4) – Cytosine - Blue (4) – Thymine - Green (5) Hydrogen bonds - White rods

16 Procedure Create 18 nucleotides Put together a 9 rung ladder of DNA Be sure to have correct base pairing After having a complete DNA molecule create 18 more nucleotides

17 DNA replication Begin to unzip DNA molecule from one end Add complimentary nucleotides to create two DNA molecules


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