DNA and anti cancer drugs Paper 2 and

DNA and anti cancer drugs

Paper 2 and 3 Main topic: Organic Sub-topic: DNA

Paper 2 and 3 Main topic: Organic Sub-topic: Anti Cancer Drugs

• DNA animation – 5 mins, clear + sharp (produced by MIT) https: //www. youtube. com/watch? v=o_-6 JXLYS-k

Not it isn’t!! Which N must bond with C 1 after condensation reaction. What must the N have to undergo condensation reaction? Why is this here? Is it a reducing sugar? Which N must bond with C 1 after condensation reaction. Is there a pattern? If the 2 is “de-oxy”; can we number the rest? What must the 1 mean? Which N must bond with C 1 after condensation reaction. What must the N have to bond? Which N must bond with C 1 after condensation reaction. Is there a pattern?

Increase level of difficulty to include the actual atoms and bonds in the nucleotides

What causes the twisting? Why is DNA such a stable molecule even though it’s only held together by H-bonds?

What’s the purpose of DNA? This is 5 minutes – it’s not on the specification, but it’s important!! https: //www. youtube. com/watch? v=zwibg. NGe 4 a. Y This is 3 minutes – it’s not on the specification, but it shows replication https: //www. youtube. com/watch? v=d. Kuby. IRi. N 84

Chemotherapy (Action of anti cancer drugs)

Shape? Co-ordination? Bonds? Bond angle? Type of isomerism?

How can guanine act as a ligand to replace a Cl? (don’t worry about the purine numbering system) Attaches to ribose sugar via Condensation reaction

note • There is actually an intermediate stage where Cl is replaced with water then the water is replaced by bond from guanine.

DNA is a highly stable molecule However DNA replicates when a specific enzyme (DNA helicase) unzips the molecule, then a series of enzymes (DNA polymerases) copies the complementary nucleotide sequences of the separated strands to create 2 identical DNA strands. The cisplatin complex is bound strongly: Pt binds more strongly to N atoms than Cl (as N more elctronegative so balances the + charge on the Pt) 2 co-ordinate bonds to the Platinum central ion Cisplatin casues the DNA molecule to change shape and allows a protein that then inhibits repair to attach to the DNA. Most DNA has natural repair enzymes that correct errors. Cisplatin causes changes which are not easily repaired. Transplatin also behaves in a similar way but because transplatin attaches to 2 separate guanines (on separate chains of DNA) this is easy for the body’s repair mechanisms to fix. Have a look https: //www. youtube. com/watch? v=Wq_up 2 u. QRDo HMG = high mobility group, a bit like a histone.

Chemotherapy targets rapidly dividing cells The chemicals like cisplatin cannot tell the difference between rapidly dividing cancer cells and other rapidly dividing cells. Consequently, side effects are associated with rapidly dividing tissues in the body: Notably – hair cells, so hair loss may occur Blood cells – so anaemia may occur as bone marrow is affected Digestive system cells – so nausea / vomiting

cancer Cancer + X amount of chemotherapy Health of patient & chances of remission cisplatin

The perfect answer to the question: Why is cisplatin used on patients when it is known to have severe side effects? (2 marks) Doctors have to balance the harm caused by side effects against the benefits of cisplatin in combatting the cancer which may have more serious health implications e. g leading to death if the cancer is untreated. How can the side effects of cisplatin be managed during treatment? Side effects can be reduced using other drugs, e. g. to reduce nausea AND the amount of cisplatin can be regulated to produce the desired effect at the minimum dose.

The perfect answer to the question: Why is the dose of cisplatin continually monitored during treatment? (2 mark) Doctors seek to find the minimum quantity of cisplatin that can reduce the cancer so as to minimise the damage caused by side effects which can seriously affect health. The perfect answer to the question: Side effects may be more severe for one individual compared to another. Why might a person with severe reactions to cisplatin have low prospects of cancer recovery? (2 marks) If doctors have to reduce the dose to reduce severe side effects, then the dose may not be high enough to combat the cancer. If they increase the dose to destroy the cancer, the side effects themselves might kill the patient.