Genetic Modification

Question 1

What is a gene?

Answer 1

A gene is a section of one strand of a DNA molecule that codes for the production of protein.

Question 2

What is recombinant DNA?

Answer 2

A section of a DNA (a gene) is snipped out of the DNA of one species and inserted into another. The new DNA is called recombinant DNA.

Question 3

What is a transgenic organism?

Answer 3

One that contains a gene or several genes from another species.

Question 4

Name the enzyme that cuts DNA:

Answer 4

Restriction endonucleases

Question 5

Name the enzyme that joins DNA

Answer 5

DNA ligases

Question 6

What are sticky ends?

Answer 6

Some restriction enzymes make a staggered cut leaving fragments of DNA with overlapping ends with complementary bases. These are called ‘sticky ends’ and are more easily joined by ligase enzymes.

Question 7

What is a vector?

Answer 7

The means of transferring the gene. E.g. Inserting a gene into a plasmid and then transferring the plasmid into a bacterium. The plasmid is the vector.

Question 8

What is a bacteriophage?

Answer 8

A virus that attracts a bacterium by attaching to the cell wall and injecting its own DNA into the bacterial cell wall. This becomes incorporated into the DNA of the host cell and eventually causes the production of many virus particles.

Question 9

How can bacteriophages be used in genetic modification?

Answer 9

If a foreign gene can be inserted into the DNA of the bacteriophage, the virus will inject it into the bacterium alongside its own genes. (This is a slightly outdated method, plasmids are a more common vector)

Question 10

Name a vector:

Answer 10

Plasmids
Bacteriophage
Agrobacterium

Question 11

How is genetically modified bacteria used in human insulin?

Answer 11

Bacteria have had human genes transferred to them that allow them to make human insulin. These transgenic bacteria are cultured by the fermenter. This helps people with diabetes who need a reliable source of insulin.

Question 12

What did diabetics do before GM? Why is GM better?

Answer 12

The only insulin available was that of other animals. This is not quite the same as human insulin and does not give the same control of blood glucose levels. Also you need a lot of it and it’s expensive. It may be rejected and those with religious beliefs or dietary requirements cannot use it.

Question 13

How is genetically modified bacteria used in enzymes for washing powder?

Answer 13

Many stains on clothing are biological. Blood is proteins, grease marks is lipids. Enzymes can digest these large, insoluble molecules into smaller, soluble ones. These then dissolve in water.

Question 14

How is genetically modified bacteria used to produce human growth hormone?

Answer 14

The pituitary gland of some children does not produce enough growth hormone so their growth is retarded. Injections of this hormone from genetically modified bacteria restore normal growth patterns.

Question 15

How is genetically modified bacteria used in the cattle industry?

Answer 15

Bovine somatotropin is cultured. This cow growth hormone increases milk yield of cows and meat production in bulls. They need more food to do this but they still make a profit.

Question 16

How is genetically modified bacteria used in human vaccines?

Answer 16

Genetically modified bacteria produce antigens of the hepatitis B virus. The body makes antibodies of these antigens without the risk of contracting the actual disease.

Question 17

How is genetically modifying a plant different to a bacteria?

Answer 17

A bacterium has one cell where as a plant has billions. To genetically modify a plant, each cell must receive the new gene.

Question 18

What are the two main stages of genetically modifying a plant?

Answer 18

1. Introducing the new gene into plant cells.

2. Producing whole plants from just a few cells.

Question 19

What is the vector for genetically modified plants?

Answer 19

Agrobacterium, it regularly inserts plasmids into plant cells.

Question 20

Process of genetically modifying plants with Agrobacterium:

Answer 20

1) DNA from another species is cut with a restriction enzyme to isolate the desired gene.
2) the plasmid from the Agrobacterium is isolated and cut with a restriction enzyme.
3) the cut plasmid is joined to the desired gene using ligase.
4) leaf discs are obtained from the plant that is to be modified.
5) these leaf disks are placed on a liquid containing the plasmids, some will take up the plasmids.
6) leaf discs are cultivated on a nutrient medium.
7) plantlets grow into whole plants whose cells now contain the foreign gene.

Question 21

What technique is used on plants the Agrobacterium cannot be used on?

Answer 21

The gene gun

Question 22

How does the gene gun work?

Answer 22

Tiny pellets of gold are coated with DNA that contains the desired gene and fired directly into the plant tissue. This genetically modified tissue can then be grown into new plants using micropropagation.

Question 23

Genetically modification of plants hopes to provide plants with:

Answer 23

• increased resistance to a range of pests and pathogens
• increased heat and drought tolerance
• increased salt tolerance
• a better balance of proteins, carbohydrates, lipids, vitamins and minerals, more nutritious crop plants.

Question 24

Why is genetic modification different in animals to plants?

Answer 24

No micropropagation techniques exist for animals, the cells must grow into a whole organism.

Question 25

What benefits are there of genetically modifying animals?

Answer 25

• increased production of a particular product, e.g. higher milk yield.
• increased resistance to disease and other parasites.
• manufacture of human antibodies.
• manufacture of specific medicinal products.
• production of low cholesterol milk.
• production of organs for transplantation (xenotransplantation).

Question 26

Process of genetically modifying animals:

Answer 26

1) the required gene is cut using restriction enzymes.
2) the DNA is injected into fertilised eggs from the donor mouse. This contains the nucleus from a sperm.
3) eggs are put into surrogate mother louse.
4) baby mice are tested for the presence of the gene.