1 ‘Special’ Past Paper Qs – 21 marksWhat type of cell division only occurs in germline cells? 1 A company has developed a drug that could treat the symptoms of an inherited disease. Before proceeding to clinical trials using volunteers, the company decides to carry out additional tests in the laboratory using stem cells. What ethical considerations might have influenced this decision to use stem cells? 2 Meiosis It is safer than using the drug directly on humans / trial subjects Or Is it right to use embryos to extract stem cells? Or Is it right to deprive sufferers of a potential treatment? Or Is it right to use stem cells rather than animals?

2 10. An atheroma may damage part X, resulting in a blood clot (thrombus). Describe the series of events that occur between the damage to part X and the formation of the clot. 3 1. Damage releases clotting factors. 2. Prothrombin (enzyme) is converted / activated / changed into thrombin. 3. Fibrinogen is converted into fibrin (by the thrombin). 4. Fibrin is insoluble / forms a meshwork (that clots the blood).

3 ‘Special’ Past Paper Qs – 21 marks3. Explain why a primary mRNA molecule is so much shorter than chromosomal DNA Explain why a final mRNA molecule is shorter than a primary mRNA molecule. 1 Only one gene is transcribed / forms mRNA. Or The primary mRNA only codes for one protein. Introns / non coding regions of genes are removed (in RNA splicing) Or The final mRNA only contains exons / coding regions of genes

4 5. What feature of this investigation makes the results reliable. 1 65. What feature of this investigation makes the results reliable? 1 6. Explain why the test tubes had to be left for 48 hours before the results were obtained. 1 The experiment was repeated at each urea concentration To allow time for the ammonia to (fully) diffuse / spread through the agar / jelly.

5 It combines with oxaloacetate to form citrate / citric acid7. Describe what happens to acetyl coenzyme A in the next stage of the respiratory pathway. 1 8. Sickle cell disease is caused by a substitution mutation in the gene that codes for haemoglobin. Describe how this form of mutation affects the structure of the gene. 1 (ii) Suggest how this might change the structure of a protein such as haemoglobin. 1 It combines with oxaloacetate to form citrate / citric acid It alters the DNA nucleotide sequence / replaces one nucleotide with another An incorrect amino acid is placed in the protein / polypeptide chain / haemoglobin. Or One amino acid is replaced by another in the protein / polypeptide chain /haemoglobin. Or The amino acid sequence is shortened (due to a stop codon).

6 9. It has been discovered that the gene which codes for fetal haemoglobin is unaffected by the substitution mutation that causes sickle cell disease. This gene is “switched off” at birth. Use this information to suggest how a drug designed to treat sickle cell anaemia in young children could function. 1 This drug could switch on the gene for fetal haemoglobin (in the child so haemoglobin is produced) or This drug could stop the gene being switched off (in the child)

7 11. What was the cardiac output of the man’s heart when his rate of oxygen uptake was 2·4 litres per minute? 1 ___ litres/min 18.72

8 12. Explain why the blood glucose concentration of individual A starts to decrease after one hour. 1Glucose is being used up by respiration Or Glucose is being removed / excreted in urine

9 13. In 2002 the number of people in England aged 35 to 44 was 6 million. How many people aged 35 to 44 were obese? 1 1.536 million /

10 ‘Special’ Past Paper Qs – 21 marks14. Name the process which the brain uses to make sense of incoming sensory information and explain how this process leads to the recognition of objects. 2 Process: Explanation: Perception It allows segregation / separation of objects from one another / their background or It allows the recognition of objects from shape descriptions stored in memory

11 ‘Special’ Past Paper Qs – 21 marks15. Explain what is meant by the term “herd immunity”. 2 A large percentage of the population have been immunised. 1 mark This means non-immune individuals are protected because there is a very low chance that they will come into contact with infected individuals. 1 mark