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 a higher yield of grain ● Cows produce a greater supply of milk ● Plants produce 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
● 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
- 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?
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?
● 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?
● 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
● 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 to cut out required gene by restriction enzymes to create sticky ends
- Vector DNA (plasmid, virus) cut using the same restriction enzymes to create
complementary sticky ends - Ligase enzymes join the sticky ends of the isolated gene and vector forming recombinant DNA
- The vector inserts the Recombinant DNA into required 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
● 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
● 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?
● The gene for toxin production in Bt can be
isolated and inserted into the DNAof crops
● Bt crops now secrete the toxin which kills any
insect larvae that feed on it
What are the benefits of Bt crops?
● 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?
● 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
● Intensive farming methods e.g. ‘battery’ farming
and the use of fertilisers and pesticides
● Biological control
What is the main advantage of intensive farming?
Increases crop yields
What are the disadvantages of intensive farming
methods?
● 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?
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
Advanced Information
Describe the process of genetic engineering in Bacteria
- DNA is cut at specific base sequences to cut out required gene by restriction enzymes to create sticky ends
- A plasmid is cut out from a bacterial cell, using the same restriction enzymes to create complementary sticky ends
- The useful gene is mixed with the plasmids. Ligase enzyme join the sticky ends of the isolated gene and the plasmid forming a recombinant plasmid
- The recombinant plasmid is put back into the bacteria and leave it to divide asexually.
- This makes many copies of the bacteria which all contain the recombinant plasmid and produce the useful product.
