Exam Questions

Question 1

Describe how a DNA profile can be made from a small sample of DNA (6 marks)

Answer 1

• PCR/polymerase chain reaction to create multiple copies of DNA.
• Credit detail of PCR e.g. temperatures at step, use of (primers/dna polymerase/dna nucleotides).
• Reference to restriction endonucleases used to produce DNA fragments
• Reference to gel electrophoresis
• Load dna fragments into wells in the agarose gel
• Apply (electric current/charge) across the agarose gel
• Reference to the use of (southern blotting/DNA probe/radioactive labelling) for visualisation.

Question 2

TB can be prevented by vaccination. Explain how a person can develop artificial active immunity following vaccination. (3)

Answer 2

• A vaccination is a dead or inactive form of the pathogen which is injected into the person
• this triggers primary immune response
• macrophages as APC’s
• APC binds to T-helper. IL-2 stimulates production of B-cells
• B-cells divide into B-effector cells which differentiate into plasma cells
• Release antibodies which kills pathogens
• Some B-cells become B-memory cells