Chapter 15 - Manpulating Genes In Organsisms

Question 1

Define selective breeding/ artificial selection

Answer 1

The process by which humans selectively develop particular phenotypic traits by choosing which animals or plants will interbreed have offspring together.

Same species, requires generations, cannot select genes (everything is transferred), little guarantee that it works, no silencing of genes possible.

Question 2

Define genetic engineering

Answer 2

The deliberate modification of the characteristics of an organism by manipulating its genetic material.

Use almost any species, short time scale, select genes, high guarantee that it works, silencing of genes possible.

Question 3

Define genetically modified organisms (GMO)

Issues?

Answer 3

Any organise whose genome has been modified.

Transgenic organism = modified using genes from another species; subgroup of GMO.

Alteration is permanent and can be inherited.

Ecological issues:
• gene transfer through cross-pollination
• pests becoming resistant over time

Social impacts:
• farmers must keep buying seeds instead of recollecting seeds.

Ownership of intellectual property issues:
• companies collecting/using genetic material without permission.

Health and safety issues:
• allergic reactions.
• animal rights.

Cultural issues:
• poses a threat to biodiversity.

Question 4

Transgenic mice

Process?

Answer 4

1. Copies of purified gene from human.
2. Micro-injection of DNA into fertilised mouse egg - injected just before the male and female pronuclei have fused random process, no control where the genes insert themselves.
3. Eggs implanted into foster mother.
   Eggs develop into mouse pups.
   Mouse pups screened to select those that have integrated the foreign DNA = transgenic.

Question 5

Transgenic plants

Methods

Answer 5

1. Physical uptake
   • gene gun = DNA-coated gold particles are accelerated at high speed into plant tissue, random, small guarantee.
2. Agrobacterium-mediated uptake
   • plasmid removed from bacterium. T-DNA (transfer DNA) is cut by a restriction enzyme.
   • foreign DNA cut by same restriction enzyme. Foreign DNA inserted into the T-DNA of the plasmid.
   • now recombinant plasmid reinserted into a bacterium.
   • bacterium is used to insert the T-DNA which carries the foreign genes, into the plant genome.
   • the plant cells are grown in culture

Question 6

Modifying embryonic cells
Aim?
How the disabling of a gene is achieved?

Answer 6

Aim = to silence or disable a specific target gene in order to identify its function by seeing what happens when the gene is inactivated.

The disabling is achieved by creating a gene that is homologous to the target gene but carries a defect in its base sequence that makes it non-functional. This is injected into an embryonic cell.