1. IB Biology 3 Chemistry of Life 3.4 DNA Replication All syllabus statements ©IBO 2007 All images CC or public domain or link to original material. http://www.flickr.com/photos/sblackley/3572873378/

2. This is a helicase molecule from E. coli The ‘-ase’ suffix should clue you in that this is an enzyme. It’s job is to break the hydrogen bonds between the strands of DNA and unwind them http://en.wikipedia.org/wiki/File:Helicase.png 3.4.1 Explain DNA replication in terms of unwinding the double helix and separating the strands by helicase, followed by the formation of the new complementary strands by DNA polymerase

3. Meet polymerase. This is DNA polymerase from a human. Its job is to help the right bases attach to the separated strands of DNA and join the bases together to make the DNA double-stranded again What sort of reaction is the polymerisation reaction?

4. The polymerisation reaction is a condensation reaction Which means…..

5. http://commons.wikimedia.org/wiki/File:DNA_replication_split_horizontal.svg DNA Polymerase adds bases from the surrounding “soup” to the separated strands Helicase DNA Polymerase

6. http://commons.wikimedia.org/wiki/File:DNA_replication_split_horizontal.svg You’ll notice that there is more than one DNA polymerase at work Helicase DNA Polymerase

7. http://commons.wikimedia.org/wiki/File:DNA_replication_split_horizontal.svg You’ll notice that there is more than one DNA polymerase at work. This is explained in 7.2 and is not required at SL Helicase DNA Polymerase

8. 3.4.2 Explain the significance of complementary base pairing in the conservation of the base sequence of DNA http://commons.wikimedia.org/wiki/File:Base_pair_AT.svg http://commons.wikimedia.org/wiki/File:Base_pair_GC.svg A fits T and C fits G, they are complementary The way the molecules fit together makes it very unlikely that they will bond with the wrong partner. So the genetic code is faithfully copied during replication When things do go wrong, we have a point mutation. (See 4.1.3 and 4.1.4) 2 H bonds 3 H bonds

9. 3.4.3 State that DNA replication is semi-conservative. Semi-conservative? http://commons.wikimedia.org/wiki/File:Mitt_Romney_2012_CPAC.jpg

10. Semi-conservative? Means: half In this case, means: conserved or saved

11. There are three ways that DNA could be copied: http://en.wikipedia.org/wiki/File:DNAreplicationModes.png

12. Each time DNA is copied, the new double stranded molecule consists of one old template strand plus a new complementary strand made from previously free bases http://www.flickr.com/photos/pagedooley/5283257753 http://www.flickr.com/photos/pagedooley/5283257753 /

13. Further information: Three of the best sites for IB-specific Biology information. The top link takes you to the PPT by Stephen Taylor