Recombinant DNA technologyAQA A-Level Biology: Mind map

Exam questions on Recombinant DNA technology

1. Beta cells of the human pancreas make large amounts of mRNA for insulin. Researchers want bacteria to make human insulin. Bacterial cells cannot remove introns from RNA. The researchers use mRNA from the beta cells as the starting material to obtain a copy of the insulin gene.
   Explain why the human insulin gene can be transcribed and translated to make insulin in the bacterial cell.2 marks
2. A plasmid vector has a single recognition site for the restriction endonuclease EcoRI, which cuts DNA leaving short single-stranded ends. A fragment of human DNA containing a gene is cut out of a chromosome using the same enzyme and then mixed with the cut plasmids.
   Explain why EcoRI cuts DNA only at one specific base sequence.2 marks
3. A forensic laboratory has only a few molecules of DNA from a crime scene. It uses the polymerase chain reaction (PCR) to make many copies of a short target sequence before analysis. The reaction mixture contains the DNA, primers, free nucleotides and a heat-stable DNA polymerase.
   Describe what happens in one cycle of PCR.3 marks