1. 7. NUCLEIC ACIDS 7. NUCLEIC ACIDS 7.1 DNA structure and replication Diana Carvajal August 2014

3. http://www.davidgalloway.co.uk/menu.swf Animation: http://www.davidgalloway.co.uk/menu.swf Animation: http://www.davidgalloway.co.uk/menu.swf

4. DNA structure suggested a mechanism for DNA replication. Semi-conservative replication: half of the parent DNA is conserved in each new DNA molecule

5. Nucleosomes help to supercoil the DNA. Supercoiling allows great lenght of DNA to be packed into a much smaller space within the nucleus. NUCLEOSOME VISUALIZATION: http://www.rcsb.org/pdb/101/motm_disscussed_en try.do?id=1aoi http://www.rcsb.org/pdb/101/motm_disscussed_en try.do?id=1aoi Utilization of molecular visualization software to analyse the association between protein and DNA within a nucleosome.

7. DNA polymerases can only add nucleotides to the 3’ end of a primer. DNA REPLICATION Animations: http://www.davidgalloway.co.uk/menu.swf http://bcs.whfreeman.com/thelifewire/content/ chp11/1103s.swf Check animation Mechanism of DNA replication

8. DNA replication is continuous on the leading strand and discontinuous on the lagging strand.

9. The proteins and enzymes involved in DNA replication include: Helicase, DNA gyrase, single strand binding proteins, DNA primase and DNA polymerases I and III.

10. DNA replication is carried out by a complex system of enzymes.

11. Some regions of DNA do not code for proteins but have other important functions. The regions of DNA that do not code for proteins are limited to: - Regulators of gene expression - introns - telomeres -genes for tRNAs.

12. Use of nucleotides containing dideoxyribonucleic acid to stop DNA replication in preparation of samples for base sequencing. Tandem repeats are used in DNA profiling.

13. IMPORTANT: Making careful observations—Rosalind Franklin’s X-ray diffraction provided crucial evidence that DNA is a double helix. (1.8) Summarize Rosalind Franklin’s and Maurice Wilkins’ investigation of DNA structure by X-ray diffraction. How do the results of the Hershey and Chase experiment provide evidence that DNA is the genetic material? Explain. Summarize Rosalind Franklin’s and Maurice Wilkins’ investigation of DNA structure by X-ray diffraction. How do the results of the Hershey and Chase experiment provide evidence that DNA is the genetic material? Explain. TOK Highly repetitive sequences were once classified as “junk DNA” showing a degree of confidence that it had no role. To what extent do the labels and categories used in the pursuit of knowledge affect the knowledge we obtain?TOK