AS 90715 Describe the role of DNA in relation to gene expression

1. Part one… AS 90715Describe the role of DNA in relation to gene expression The Structure of DNA Take me to NZQA Documents relating to this standard

2. Contents • DNA in your cells (revision stuff you probably already know) • DNA Structure • Complimentary bases • RNA structure • Anti-parallel strands • Review Questions

3. Stuff that any respectful Bio student really should know… • Deoxyribonucleic Acid- (learn how to spell it) • The number of chromosomes a species has does not indicate higher order. • Human – 46 • Kangaroo – 12 • Pea – 6 • Shrimp -92 DNA – • This is a chromosome? – nope it is two chromosomes. This is 2 identical chromosomes joined together • A single chromosome looks like – • Once a chromosome replicates – then it forms the sausage (chromatid) structure attached to its replicated copy.

4. Chromatid • To form a chromatid the DNA strand winds around protiens (histomes) that package the strand into a lovely organised ‘bundle’ • Why – because the strand is incredibly long ‘On the average, a single human chromosome consists of DNA molecule that is about 5 centimetres long’ The World Book Encyclopedia

5. Karyotypes This slide is revision from L2 – but lets make sure we have it right! What does this image represent? Is it a.. Chromosome Replicated chromosome Homologous pair Diploid chromosome Karyotypes are images of an organisms replicated chromosomes taken of a cell as it prepares to divide (metaphase) Biozone Pg 60 Q1-6

6. Genome This slide is revision from L2 – but lets make sure we have it right! What does this image represent? Is it a.. Chromosome Replicated chromosome Homologous pair Diploid chromosome Karyotypes are images of an organisms replicated chromosomes taken of a cell as it prepares to divide (metaphase) Biozone Pg 60 Q1-6

7. DNA Structure • DNA strands are made up of Nucleotides. • There are only 4 different nucleotides

8. DNA Structure For the Chemists (not examinable) When labeling the C atoms on the sugar they are given numbers (why? Because chemists get a kick out of it) • Purines (A, G) 2 rings • Pyrimadines (C, T) 1 ring Hydrogen bonds

9. RNA Structure RNA is similar to DNA. The difference is: • RNA is single stranded • RNA has the base Uracil instead of Thymidine • The sugar in the nucleotide is different. Donald and Ronald - DNA and RNA Double strand - single strand Biozone Pg 66 Q1-5

10. Differences between DNA and RNA • Also: • mRNA is shorter and mRNA can travel into cytoplasm

11. Anti-parallel structure (DNA) • Both these images show the same idea

12. Anti-parallel structure (DNA) • This diagram shows a lot of stuff not yet discussed. • What you need to understand at this point • When an enzyme (DNA polymerase) travels along a strand of DNA it travels in the 3’ to 5’ direction of the original strand DNA Polymerase travels 3’ to 5’ on original strand

13. REVIEW QUESTIONS ONDNA STRUCTURE!

14. Review Question 1 • What does this represent • Name the three parts • The green bit has four different types – name them!

15. Review Question 2 • What is this? • How many of these does a diploid human cell contain • If a cell contains something that looks like this then it is about to ________?

16. Review Question 3 • Name three key differences between RNA and DNA. (Click for answer)