Changing Genes (Biology) Flashcards
(29 cards)
What is selective breeding?
The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes.
Outline the main steps involved in selective breeding.
- Identify a desired characteristic e.g. disease resistance.
- Select parent organisms that show the desired traits and breed them together.
- Select offspring with desired traits and breed them together.
- Process repeated until all offspring have the desired traits.
What is the main advantage of selective breeding?
Creates organisms with desired features:
- Crops produce a higher yield of grain
- Cows produce a greater supply of milk
- Plants produce larger fruit
- Domesticated animals
Other than agriculture, where else is selective breeding useful?
- In medical research
- In sports e.g. horse racing
Outline the disadvantages of selective breeding. (4)
- Reduction in the gene pool (which becomes especially harmful if sudden environmental change occurs)
- Inbreeding results in genetic disorders
- Development in other physical problems e.g. respiratory problems in bulldogs
- Potential to unknowingly select harmful recessive alleles.
How can plants be cloned? (2)
- Taking plant cuttings
- Tissue culture
What is tissue culture?
A method of growing living tissue in a suitable medium.
Describe how plants are grown using tissue culture.
- Select a plant that shows desired characteristics.
- Cut multiple small sample pieces from meristem tissue.
- Grow in a petri dish containing growth medium.
- Transfer to compost for further growth.
What must be ensured when preparing tissue culture?
Ensure aseptic conditions to prevent contamination by microorganisms.
What does the growth medium contain?
Nutrients and growth hormones.
What are the advantages of growing plants by tissue culture? (4)
- Fast and simple process
- Requires little space
- Enables the growth of many plant clones with the same desirable characteristics
- Useful in the preservation of endangered plant species.
What are the disadvantages of growing plants by tissue culture? (4)
- Reduction in the gene pool
- Plant clones often have a low survival rate
- Could unknowingly increase the presence of harmful recessive alleles.
Why is animal tissue culturing useful?
- Useful in the preparation of tissue samples for medical research.
- Enable the investigation of how different factors may affect a specific animal tissue, without harming the animal itself.
Describe how animal tissue cultures are prepared.
- Extract a sample tissue from an animal.
- Use enzymes to separate cells within the sample.
- Grow in a culture vessel containing growth medium.
- Once grown, store the sample.
What is genetic engineering?
- The modification of a genome of an organism by the insertion of a desired gene from another organism.
- Enables the formation of an organism with beneficial characteristics.
Describe the process of genetic engineering.
- DNA is cut at specific base sequences by restriction enzymes to create sticky ends.
- Vector DNA cut using the same restriction enzymes to create complementary sticky ends.
- Ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DNA.
- Recombinant DNA mixed up and ‘taken up’ by target cells.
What is a vector?
- a structure that delivers desired gene into the recipient cell e.g. plasmids, viruses.
Describe the benefits of genetic engineering. (3)
- Increased crop yields for growing population e.g. herbiside-resistance, disease resistance
- Useful in medicine e.g. insulin-producing bacteria, anti-thrombin in goat milk.
- GM crops produce scarce resources e.g. GM golden rice produces beta carotene (source of vitamin A in the body )
Describe the risks of genetic engineering (4)
- Long term effects of consumption of GM crops unknown
- Negative environmental impacts e.g. reduction of biodiversity, impact on food chain, contamination of non-GM products forming ‘superweeds’.
- Late-onset health problems in GM animals
- GM seeds are expensive. LEDC’s may be unable to afford them or may become dependent on businesses that sell them.
What is Bacillus thuringiensis (Bt)?
- Insect larvae are harmful to crops.
- Bt is a bacterium which secretes a toxin that kills insect larvae.
How is genetic engineering used to protect crops against insects?
- The gene for toxin production in Bt can be isolated and inserted into the DNA of crops.
- Bt crops now secrete the toxin which kills any insect larvae that feed on it.
What are the benefits of Bt crops (3)?
- Increase crop yields
- Lessens the need for artificial insecticides
- Bt toxin is specific to a certain insect larvae so is not harmful to other organisms that ingest it.
What are the risks of Bt crops (3)?
- Long term effects of consumption of Bt crops unknown
- Insect larvae may become resistant to the Bt toxin
- Killing insect larvae reduces biodiversity
Outline the agricultural methods of increasing food production. (2)
- Intensive farming methods (e.g. ‘battery’ farming and the use of pesticides and fertilisers)
- Biological control
