Topic 7.3 Gene Technology

Question 1

Gene technology

Answer 1

• The manipulation of genes in living organisms.
• Genes from one organism may be inserted into another.

Question 2

Recombinant DNA

Answer 2

• DNA that has been formed artificially by combining DNA from different organisms.
  (Marker genes are used to identify recombinant cells).

Question 3

The first step in Recombinant DNA

Answer 3

• Isolating the DNA/gene of interest.
• Detergent is used to isolate the DNA from a sample.
• It breaks down the membrane.
  (Protein may need to be removed using digestive enzymes).
• There are three ways to isolate the gene:
  1) Using reverse transcriptase
  2) Using restriction endonuclease
  3) The Gene Machine

Question 4

Isolating gene: Using reverse transcriptase

Answer 4

• RNA is taken from a cell that produces the required protein.
• Reverse transcriptase causes a reaction in which complimentary DNA (cDNA) is made from mRNA and DNA nucleotides.
• The result is a single strand of cDNA.
  —> DNA polymerase and free nucleotides are used to produce a double strand of cDNA

Question 5

Isolating gene: Using restriction endonuclease

Answer 5

• Gene can be removed from the chromosome using restriction endonuclease.
• Different enzymes cut the DNA at a different positions.
• This is called a recognition sequence.
  (Restriction enzymes are made by bacteria).

Question 6

Isolating gene: Gene Machine

Answer 6

• Scientists examine amino acid sequencing in desired protein.
• Creates small non overlapping section of DNA which are joined to create the desired gene.
• PCR is used to amplify this copy.

Question 7

Gene engineering

Answer 7

1) Isolating required gene (using restriction endonuclease).
2) Inserting the gene in a ‘vector’ (using ligase).
3) Transformation- the gene is delivered into the required cell for protein growth (using microinjection).
4) Identification of host cells that have taken up the gene.
5) Grow cells with the new gene on a large scale (cloning).

Question 8

Transformation

Answer 8

• The vector needs to be placed back into the host cells.
  1) Place the host cells in ice cold calcium chloride solution to make cell walls more permeable.
  2) The plasmids are then added to the mixture is heat shocked (42°C for 2 minutes) which encourages the cells to take up the plasmids.

Question 9

Transformation: Gene guns

Answer 9

• A method for the physical introduction of DNA into plant cells containing cell walls:
  -DNA is shot into the cell at a high speed.
  (Microscopic gold pellets are coated with copies of the DNA fragment).

Question 10

Transformation: Liposome wrapping

Answer 10

• The gene to be inserted is wrapped in liposomes (spheres formed from a lipid bilayer).
• These fuse with the cell membrane and can pass through it to deliver the DNA.

Question 11

Transformation: Microinjection

Answer 11

Injecting DNA directly into cells (often used in animals).

Question 12

Transformation outcomes

Answer 12

• Successful transformation (gene is in plasmid)- 5% likely.
• Unsuccessful transformation (gene is outside the plasmid).
• No plasmid.

Question 13

How do we make GM plants?

Answer 13

• Usually use the bacterium Agrobacterium tumerfacians which causes tumors in plants.
• Agrobacterium contains Ti plasmid, which transfers genetic material into plants.
• GM plant tissue can then be grown by tissue culture (as plant cells remain totipotent).
• Plants are cloned.

Question 14

GM Soya beans

Answer 14

• They have been made resistant to herbicides.
• Fatty acid balance.

Question 15

Knockout mice

Answer 15

• A lab mouse in which one or more genes have been turned off or ‘knocked out’.
  —> To create a knockout mouse, scientists genetically engineer the animal by disrupting a gene of interest.

Question 16

Why does recombinant DNA technology work?

Answer 16

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 17

How do you insert a vector into a host cell?

Answer 17

The host cells are mixed with the vectors in an ice-cold solution, then heat shocked to encourage the cells to take up the vectors.

Question 18

What is a transgenic plant?

Answer 18

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

Question 19

Advantages of the widespread use of genetic modification

Answer 19

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

Question 20

Disdvantages of the widespread use of genetic modification

Answer 20

• Reduced biodiversity.
• Unknown effect son health.
• Cross-pollination could result in herbicide-resistant weeds.
• May increase costs for farmers.