recombinant DNA technology

Question 1

A laboratory has oat plants containing the resistance gene and a supply of plasmids.

Describe how bacteria may be produced which have the resistance gene in their plasmids (6)

Answer 1

1 cut desired gene (from DNA) of oat plant;
2 using restriction endonuclease / restriction enzyme;
3 cut plasmid open;
4 with (same) restriction endonuclease
5 ref. sticky ends
6 use (DNA) ligase to join
7 return plasmid to (bacterial) cells;
8 use of Ca2+

Question 2

The polymerase chain reaction (PCR) can be used to produce large quantities of DNA.
Describe how the PCR is carried out (6)

Answer 2

1 DNA heated to 90 to 95°C;
2 strands separate;
3 cooled / to temperature below 70°C
4 primers bind;
5 nucleotides attach;
6 by complementary base pairing;
7 temperature 70 - 75°C;
8 DNA polymerase joins nucleotides together;
9 cycle repeated;

Question 3

Scientists can increase the nutritional value of potatoes by genetically engineering potato plants.
A gene which results in increased protein production has been removed from cells of an amaranth plant and inserted into cells of a potato plant.

(a) Describe how a gene could be removed from cells of an amaranth plant and inserted into cells of a potato plant (6)

Answer 3

1. (cut out gene using an) endonuclease / restriction enzyme;
2. recognition site;
3. sticky ends;
4. use the same enzyme to cut;
5. plasmid / virus / potato DNA;
6. fixed by ligase;
7. method of introducing vector e.g. micropipette / virus injects DNA /
8. remove plant cell wall;

Question 4

Plasmids can be modified by genetic engineering and inserted into bacteria. These bacteria can then make useful substances normally made by another organism.
Explain how modified plasmids are made by genetic engineering and how the use of markers enable bacteria containing these plasmids to be detected (6)

Answer 4

1. isolate wanted gene / DNA from another organism;
2. using restriction endonuclease to get DNA and produce sticky ends;
3. use ligase to join wanted gene to plasmid;
4. also include marker gene e.g. antibiotic resistance;
5. add plasmid to bacteria to grow (colonies)then (replica) plate onto medium where the marker gene is expressed;
6. bacteria not killed have antibiotic resistance gene and the wanted gene;