Cambridge International A Level Biology Revision Guide

Chapter 19: Genetic technology
End-of-chapter questions
1 Different enzymes are used in the various steps involved in the production of bacteria capable of synthesising a
human protein. Which step is catalysed by a restriction enzyme?
A cloning DNA
B cutting open a plasmid vector
C producing cDNA from mRNA
D reforming the DNA double helix [1]
2 What describes a promoter?
A a length of DNA that controls the expression of a gene
B a piece of RNA that binds to DNA to switch off a gene
C a polypeptide that binds to DNA to switch on a gene
D a triplet code of three DNA nucleotides that codes for ‘stop’ [1]
3 Which statement correctly describes the electrophoresis of DNA fragments?
A Larger fragments of DNA move more rapidly to the anode than smaller fragments.
B Positively charged fragments of DNA move to the anode.
C Small negatively charged fragments of DNA move rapidly to the cathode.
D Smaller fragments of DNA move more rapidly than larger fragments. [1]
4 The table shows enzymes that are used in gene technology. Copy and complete the table to show the role of
each enzyme.
Enzyme
DNA ligase
DNA polymerase
restriction enzymes
reverse transcriptase
Role
[4]
487
5 Rearrange the statements below to produce a flow diagram showing the steps involved in producing bacteria capable of
synthesising a human protein such as human growth hormone (hGH).
1 Insert the plasmid into a host bacterium.
2 Isolate mRNA for hGH.
3 Insert the DNA into a plasmid and use ligase to seal the ‘nicks’ in the sugar–phosphate chains.
4 Use DNA polymerase to clone the DNA.
5 Clone the modified bacteria and harvest hGH.
6 Use reverse transcriptase to produce cDNA.
7 Use a restriction enzyme to cut a plasmid vector. [4]