8. Control of gene expression EQs

Question 1

Suggest and explain why it is harder to determine the proteome of a plant from its genome that it is to determine the proteome of a bacterium from its genome (2 marks)

Answer 1

1. bacteria have fewer non-coding regions
2. plants have regulatory genes

Question 2

Describe how a gene can be isolated from human DNA. (2 marks)

Answer 2

1. use restriction endonuclease
2. to cut DNA in specific place

Question 3

Cut plasmids and lengths of foreign DNA can join. What features of their ends
allows them to join? (2 marks)

Answer 3

1. sticky ends
2. complementary

Question 4

Suggest two reasons why it was better to start with mRNA from pancreas cells rather than with the DNA from these cells. (2 marks)

Answer 4

1. multiple copies of mRNA
2. introns present in DNA

Question 5

What is the role of a primer in ‘in vitro’ cloning? (1 mark)

Answer 5

enables replication / sequencing to start

Question 6

Suggest one use of the polymerase chain reaction. (1 mark)

Answer 6

replication of DNA from crime scene

Question 7

Why is the DNA polymerase used heat-stable? (1 mark)

Answer 7

not denatured

Question 8

Explain the shape of the curve during ‘in vitro’ cloning? (2 marks)

Answer 8

1. doubling (of DNA) each cycle;
2. but very low numbers to start with, so appears flat then
   exponential growth;

Question 9

Explain one way in which the polymerase chain reaction differs from DNA replication in a cell. (2 marks)

Answer 9

1. primer added in PCR;
2. to initiate replication

Question 10

In a particular PCR, two different primers are added to the DNA. Suggest why two
different primers are required. (1 mark)

Answer 10

because the sequences at the ends of the target sequence
are different