8- Recombinant DNA =)

Question 1

A scientist produced transgenic zebrafish.
She inserted copies of this GH gene into plasmids.
Describe how enzymes could be used to insert the GH gene into a plasmid. (2)

Answer 1

• restriction endonucleases cut plasmid –> sticky ends
• ligase joins gene + plasmid

Question 2

Microinjection of DNA into fertilised egg cells is a frequent method of producing transgenic fish.
However, the insertion of the transferred gene into nuclear DNA may be delayed. Consequently, the offspring of transgenic fish may not possess the desired characteristic.
Suggest and explain how delayed insertion of the GH gene could produce offspring of transgenic fish without the desired characteristic. (2)

Answer 2

1. cell division occurred before gene added
2. cells producing gametes x receive genes

Question 3

Suggest two features of the structure of different proteins that enable them to be separated by gel electrophoresis. (2)

Answer 3

1. no. of a.a.
2. R groups
3. charge

Question 4

Explain the role of reverse transcriptase in RT-PCR (reverse transcriptase-polymerase chain reaction). (1)

Answer 4

produce cDNA using mRNA

be specific!!!

Question 5

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

Answer 5

• restriction endonucleases cut DNA
• at specific base seq

Question 6

Scientists manufactured large quantities of human insulin using genetic engineering.
They started by isolating mRNA from pancreas cells. From this they produced DNA which coded for insulin.
Suggest two reasons why it was better to start with mRNA from pancreas cells rather than with DNA from these cells. (2)

Answer 6

1. mRNA spliced - x introns
2. amount of mRNA > DNA
3. specific (insulin) mRNA found in pancreas cells

Question 7

Plasmids are often used as vectors in genetic engineering.
What is the role of a vector? (1)

Answer 7

Transfer genes from 1 organism to another

Question 8

Describe the role of restriction endonucleases in the formation of plasmids that contain donor DNA. (2)

Answer 8

1. cut open plasmid
2. cut donor DNA- remove gene
3. same r.e. used to cut both plasmid + DNA – cuts at same base seq.
4. sticky ends w/ bases exposed
5. complementary base pairing betw. strands

Question 9

Describe the role of DNA ligase in the production of plasmids containing donor DNA. (1)

Answer 9

forming phosphodiester bonds (annealing)

Question 10

Sticky ends are useful in genetic engineering.
Explain how. (2)

Answer 10

• joining 2 pieces of DNA
• by complementary base pairing

Question 11

A plasmid may be used as a vector.
Explain what is meant by a vector. (2)

Answer 11

- carrier of DNA/ gene
- into cell/ other organism

Question 12

Molecular biologists often use plasmids which contain antibiotic resistance genes.
Explain the reason for this. (2)

Answer 12

• act as marker gene
• ✔ detection of cells containing plasmid

Question 13

Recombinant DNA technology can involve the transfer of fragments of human DNA into bacteria. The bacteria are then used to produce human proteins.
Give two reasons why bacteria are able to use human DNA to produce human proteins. (2)

Answer 13

1. genetic code is universal
2. mechanism of transcription is universal
3. mechanism of translation is universal

x DNA is universal!!

Question 14

Recombinant DNA technology can involve the transfer of fragments of human DNA into bacteria. The bacteria are then used to produce human proteins.
Suggest and explain one reason why bacteria might not be able to produce every human protein. (1)

Answer 14

• x splice pre-mRNA –> x remove introns
• x golgi –> x modify proteins
• x have transcription factors –> x carry out transcription

Question 15

The enhancer only stimulates region M in the milk-producing glands of a goat.
Suggest an explanation for the importance of the enhancer being included in the DNA fragment transferred. (1)

Answer 15

milk easily extracted from goat