Genetic Revolution : Genetic Engineering and Cloning

Question 1

what does genetic engineering involve?

Answer 1

• transferring genes from one organism to another- often to a totally unrelated species

Question 2

what are transgenic organisms?

Answer 2

• organisms which have received genes from another species

Question 3

what are vectors?

Answer 3

• can be used to carry the DNA of one organism into another

Question 4

what is an example of how a vector has been used?

Answer 4

• e.g. a vector that has been used to introduce foreign DNA into bacterial cells is the bacteriophage (a type of virus)
• the bacteriophage attacks a bacterium by injecting its own DNA into the bacterial cell
• this DNA becomes incorporated into the DNA of the hose cell and eventually cases the production of many virus particles

Question 5

what are bacteria?

Answer 5

• microscopic single-celled organisms with cytoplasm, cell membranes and cell walls but without a proper nucleus
• the bacterial DNA is found in the cytoplasm as a circular chromosome (or loop) of DNA
• in addition to this main loop of DNA, bacteria have small, circular pieces of DNA called plasmids

Question 6

what does type 1 diabetes mean?

Answer 6

• their pancreas’ do not produce insulin
• therefore they must inject themselves with insulin in order to lower their blood sugar keveks

Question 7

how is human insulin made?

Answer 7

• first the human insulin gene must be located on the chromosome
• the gene is then cut from the rest of the chromosome using a special enzyme called a DNA restriction enzyme.
• a plasmid is removed from the bacterium (E.coli) and cut open with the same DNA restriction enzyme
• each DNA restriction enzyme cuts at a specific sequence of bases, producing short single stranded sections called sticky ends
• the human insulin gene and plasmid join together due to complementary base pairing at the sticky ends
• a DNA ligase enzyme form bonds between the nucleotides to make this a single piece of DNA
• we say the plasmid is now recombinant DNA - it is a combination from two different sources
• the plasmid is carrying the human DNA is referred to as a vector
• the transgenic bacteria are then placed into a fermenter in order to increase in number
• this is sterilised prior to use. the nutrient medium and air entering the system is also sterilised to prevent the growth of pathogens or competing microorganisms
• if the bacteria have enough nutrients and are kept at their optimum conditions they will begin to produce human insulin
• this is achieved by providing oxygen via the air line ; stirring the mixture to prevent clumping and a shortage of nutrients ; monitoring temperature and cooling the fermenter if needed ; adding more nutrient medium
• the insulin is secreted by the bacteria. it is then collected from the fermenter, purified and distributed

Question 8

how do you genetically modify plants?

Answer 8

• a different technique has to be used since there are billions of cells in plants and each cell must receive the new gene

Question 9

what two stages does the procedure to genetically modify plants consist of?

Answer 9

• introducing the new gene or genes into plant cells
• producing whole plants from just a few cells (tissue culture)

Question 10

what is the bacteria which is now used to genetically modify the plants?

Answer 10

• agrobacterium tumefaciens is used since it regularly inserts plasmids into plants cells, adding genes to the plant chromosomes

Question 11

what traits can be added to plants?

Answer 11

• higher yield
• ability to produce extra nutrients e.g. golden rice produces more vitamin A (preventing blindness)
• resistance to extremes in weather e.g. drought tolerance
• resistance to pests e.g. by producing toxins to beetle larvae
• resistance to disease/pathogens

Question 12

what are the advantages of genetically modified plants?

Answer 12

• more precise method than selective breeding
• higher crop yield/better food quality
• less pesticide/herbicide used so less pollution
• disease resistant/pest resistant/herbicide resistance

Question 13

what are the disadvantages of genetically modified plants?

Answer 13

• not accepted by public
• long term affects unknown
• may affect food chains or environment
• reduces variation

Question 14

why would breeders want to clone plants?

Answer 14

• often breeders only have a small number of plants with desirable features
• they need to increase the numbers quickly and if they relied on the plant’s own method of reproduction they would have to wait a long time
• also they want the daughter plants to be genetically identical so have the exactly the same desirable features as the parent plant

Question 15

how is it possible to propagate many plants?

Answer 15

• by taking cuttings from leaves, roots or stems
• these methods have been used for many years and is called Artificial Propagation

Question 16

what is a method of producing much larger numbers of genetically identical plants?

Answer 16

• tissue culture or micro propagation
• this is particularly useful for plants that are difficult to propagate by seeds or cuttings
• whole plants are grown from individual cells for from small parts of plant tissue

Question 17

what is micro-propagation and describe it?

Answer 17

• it is complex and requires lab equipment
• in stage 1, a small section (explant) is cut from the desired plant. it is sterilised and placed onto a nutrient gel, where it grows into a small ball of cells (callus)
• small groups of cells are then taken from the callus and enter stages 2-4 above. plant hormones are used to stimulate shoot and root growth. these small bundles of cells grow into individual cloned plants
• if the plant has desirable features such as a high resistance to a specific pest, then the young plants will have these features too. micro-propagation can also be used to increase the number of a genetically modified plant

Question 18

is it important to keep the less popular varieties?

Answer 18

• yes
• they may contain genes which we might find useful one day, such as ones which help them to resist a particular kind of disease

Question 19

what are gene banks?

Answer 19

• things that are now being kept for most kinds of plants, where seeds of all different varieties are kept, in case breeders may want to use them in years to come

Question 20

describe a different technique which can be used to clone mammals?

Answer 20

• a body cell is taken from sheep A (female)
• DNA is extracted from it
• an egg cell is taken from sheep B (female)
• the DNA is extracted as a whole nucleus
• the nucleus is removed
• DNA from sheep A is fused with egg cell from sheep B and an electric shock is used to fuse the nucleus and the empty (enucleated) egg cell; this also stimulates mitosis
• the fused cell develops into embryo which is placed in uterus of foster mother
• lamb is clone of sheep A

Question 21

who was the first cloned mammal and when was she cloned?

Answer 21

• was a sheep named dolly in 1997

Question 22

what is the research currently being done into the possibility of cloning human body parts for transplant surgery?

Answer 22

• pigs could be genetically modified to have human antigens (recognition proteins) on their cell membranes
• this could allow pig organs to be transplanted into humans as it would reduce the immune response against the organ and risk of rejection

Question 23

what are the complications regarding cloning pigs and transplanting their organs?

Answer 23

• ethical considerations
• xenotransplantation (transplants between different species) could lead to viruses being transferred between species

Question 24

what is another alternative to cloning pigs and transplanting their organs?

Answer 24

• another possibility would be to genetically engineer goats or similar animals to produce human proteins, e.g. antibodies in their milk
• the genetically modified pigs could be clones to increase the population
• the proteins could be collected from the milk and used to treat patients with weak immune systems, such as cancer or HIV patients, or other health conditions