Topic 7.4 Gene technology

Question 1

What is meant by recombinant DNA technology?

Answer 1

The transfer of DNA fragments from one organism to another.

Question 2

Why does recombinant DNA technology work?

Answer 2

Because the genetic code is universal, and therefore transcription and translation occur by the same mechanism and result in the same amino acid sequence across organisms.

Question 3

Summarise the process of using reverse transcriptase to produce DNA fragments

Answer 3

mRNA complementray to the target gene is used as a template. It is mixed with free nucleotides which match up to their base pairs, and reverse transcriptase which forms the sugar-phosphate backbone, to create cDNA (complementary DNA)

Question 4

Summarise the process of using enzymes to produce DNA fragments

Answer 4

Restriction endonucleases (RE) cut DNA at specific sequences. Different REs cut at the same sequance. Therefore using particular REs allows you to cut out a certain gene of interest.

Question 5

Give ways in which recombinant DNA can be inserted into other cells

Answer 5

• Virus vectors
• Gene guns
• Liposome Wrapping (DNA wrapped in liposomes - fuse with cell membrane)
• Microinjection (micropippete and micromanipulation)

Question 6

Summarise the process of inserting a DNA fragment into a vector

Answer 6

A plasmid (circular DNA from a virus) is used as the vector, and is cut using the same restriction enzymes as the DNA, so that the ends are complementary. DNA ligase joins the fragment and plasmid together.

Question 7

Summarise the process of inserting a vector into a host cell

Answer 7

Known as cell transformation. The host cells (bacteria) are mixed with the vectors in an ice-cold solution, then heat shocked to encourage the cells to take up the vectors. The cells can then be grown and the DNA fragment will be cloned.

Question 8

Describe how gene guns work

Answer 8

Microscopic gold pellats are coated with copies of the DNA fragment, which are then propelled at high speed into cells.

Question 9

Describe ways to identify recombinant cells

Answer 9

Marker genes can be inserted into plasmids at the same time as DNA fragments e.g. antibiotic resistance genes. The transformed cells are then placed on a plate with antibiotics, so only the ones that successfully took up the vector will grow.

Or fluorecence

Question 10

What are ‘knockout mice’ and why are they useful?

Answer 10

Mice with one or more genes silenced. Can be used to investigate gene function, or create animal models of disease to allow research and testing of treatments.

Question 11

What is meant by transgenic plants?

Answer 11

Genetically modified plants, which contain genetic material from an unrelated organism

Question 12

Explain the process of producing transgenic plants

Answer 12

Ti plasmid extraced from bacterium, gene inserted, and then returned. Plant is then infected with the bacteria. This will produce a gall, containing cells that contain the inserted gene. These cells can be used to grow a whole new plant.

Question 13

Give an example of a genetically modified plant and the benefits of this

Answer 13

Soya beans. Linoleic acid (polyunsaturated) is replaced by oleic acid (monounsaturated). This is oxidised less easily and so prolongs shelf life, as well as being healthier.

Question 14

Give some advantages of the widespread use of genetic modification

Answer 14

• Improve nutritional value of foods
• Greater crop yeilds
• Less need for pesticides
• Reduces need for land clearing

Question 15

Give some disadvantages of the widespread use of genetic modification

Answer 15

• Reduced biodiversity
• Unknown effects on health
• Cross-pollintation could result in herbicide-resistant weeds
• May increase costs for farmers