Topic 4 – Natural Selection and Genetic Modification- Changing Genes Flashcards
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 the 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 desirable features. crops produce higher yield of grain cows produce greater supply of milk plant produces larger fruit domesticated animals
Other than in 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 of other physical problems e.g. respiratory problems in bulldogs
Potential to unknowingly select harmful recessive alleles
How can plants be cloned?
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 (biology only)
- 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 cultures? (biology only)
Ensure aseptic conditions to prevent contamination by microorganisms
What does the growth medium contain? (biology only)
nutrients and growth hormones
What are the advantages of growing plants by tissue culture?
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?
Plant clones often have a low survival rate
Could unknowingly increase the presence of harmful recessive alleles
reduction in gene pool
Why is animal tissue culturing useful?
Useful in the preparation of tissue samples for medical research
Enables 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 of 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 the 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 with and ‘taken up’ by target cells
What is a vector?
A structure that delivers the 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. herbicide-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 in biodiversity, impact on food chain, contamination of non-GM crops forming ‘superweeds’
Late-onset health problems in GM animals
GM seeds are expensive. LEDCs 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? (biology only)
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) (biology only)
Increased crop yields (fewer crops damaged)
Lessens the need for artificial insecticides
Bt toxin is specific to 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 fertilisers and pesticides
● Biological control
What is the main advantage of intensive farming? (biology only)
increases crop yield
What are the disadvantages of intensive farming methods? (3) (biology only)
Fertilisers can wash into nearby water sources and cause eutrophication
The use of herbicides and insecticides reduces biodiversity
‘Battery’ farming is often seen as unethical
What is biological control? (biology only)
When a new organism (often a predator) is introduced into an ecosystem to control a pest or pathogen
What are the advantages of using biological control to increase food production?
The results of biological control generally last for a long period of time
The effects on wildlife are less severe
What is the risk of using biological control?
Risk of the control organism becoming a pest itself
