Genetic Modification Flashcards
All 35 cards in this deck
What is selective breeding?
Choosing organisms with desired characteristics and breeding them together over many generations so the offspring show those characteristics.
What are the steps of selective breeding?
e.g. breeding cows for a higher milk yield
- Choose parents with the desired characteristic — cows with the highest milk yield
- Breed them together — take offspring from these parents
- Select the best offspring and repeat over many generations — milk yield increases each generation
Give two characteristics that food plants are commonly selectively bred for.
Higher crop yield and disease resistance.
True or false? Selective breeding introduces new genes into a species.
False. It only increases the frequency of alleles that are already present in the population.
State two problems caused by selective breeding.
Reduced genetic variation, and a greater chance of inherited defects/disease in the population.
How do breeding programmes try to maintain genetic variation?
By keeping breeding records/pedigrees to avoid breeding close relatives, and by using gene or sperm banks to reintroduce different alleles.
What is tissue culture?
Growing cells or small pieces of tissue on a sterile nutrient medium to produce genetically identical new cells or organisms.
What are the steps of plant tissue culture?
e.g. producing many orchids from one parent plant
- Take a small tissue sample (explant) from the parent plant — a few cells from the orchid
- Grow it on a sterile nutrient medium with plant hormones — cells divide to form a mass of tissue
- Transfer the plantlets to soil — many orchids identical to the parent
Why must tissue culture be carried out in aseptic (sterile) conditions?
To stop microorganisms contaminating the culture and killing the growing cells.
Give two advantages of tissue culture in plant breeding programmes.
Large numbers of identical plants with the desired characteristics can be made quickly, and rare or endangered plants can be preserved.
Give one advantage of tissue culture in medical research.
Identical cells can be grown to test drugs or study disease, so results are not affected by genetic differences between cells.
True or false? Plants produced by tissue culture are clones of the parent plant.
True. They are grown from the parent's cells by mitosis, so they are genetically identical.
What is genetic engineering?
Modifying the genome of an organism by inserting a gene from another organism to introduce a desirable characteristic.
What is a genome?
All of the genetic material (DNA) of an organism.
What is a genetically modified (GM) organism?
An organism whose genome has been changed by genetic engineering, usually by inserting a gene from another organism.
True or false? Genes can only be transferred between organisms of the same species by genetic engineering.
False. Genes can be transferred between completely different species, e.g. a human gene into a bacterium.
Give one medical example of genetic engineering.
Inserting the human insulin gene into bacteria so they produce human insulin.
What are the main stages of genetic engineering?
e.g. putting the human insulin gene into a bacterium
- Cut out the gene and cut open the vector with the same restriction enzyme — both have complementary sticky ends
- Join the gene into the plasmid using ligase — a recombinant plasmid
- Insert the vector into the host cell — the bacterium takes up the plasmid and makes insulin
What does a restriction enzyme do in genetic engineering?
Cuts DNA at a specific sequence, leaving sticky ends.
What are sticky ends?
Short sections of unpaired bases left at the cut ends of DNA by a restriction enzyme.
What does ligase do in genetic engineering?
Joins the gene into the cut vector by sealing the DNA together.
What is a vector in genetic engineering?
Something used to carry a gene into a host cell, e.g. a bacterial plasmid or a virus.
True or false? The gene and the plasmid must be cut with the same restriction enzyme.
True. This gives them complementary sticky ends so the bases pair up and they can be joined.
Which gene is taken from Bacillus thuringiensis and put into crop plants, and why?
A gene for a toxin (Bt toxin) that kills insect pests, giving the crop insect resistance.
Give two advantages of growing insect-resistant GM crops.
Higher crop yields because fewer plants are eaten by pests, and less pesticide needs to be sprayed.
Give two disadvantages of growing GM crops.
GM seed is expensive for farmers, and the transferred gene may spread to wild plants or harm non-pest insects.
Give one advantage and one disadvantage of using fertilisers to increase food production.
Advantage: they replace minerals in the soil so crops grow bigger and yields increase. Disadvantage: they are expensive and can pollute nearby water.
What is biological control?
Using a natural predator, parasite or pathogen to reduce the number of a pest species.
Give one advantage and one disadvantage of biological control.
Advantage: no chemical pesticides are needed, so no chemical build-up in food chains. Disadvantage: the control organism may become a pest itself or eat other species.
Give two benefits of genetic engineering in medicine.
Large amounts of human proteins such as insulin can be made cheaply, and gene therapy may treat inherited disorders.
Give two ethical objections raised against genetic engineering.
It is seen as 'unnatural' or interfering with nature, and concerns that it could lead to choosing human characteristics ('designer babies').
Give one advantage of genetic engineering over selective breeding.
It is much faster and genes can be transferred between different species, giving characteristics the species could never have gained by breeding.
True or false? Insect pests can become resistant to the Bt toxin produced by GM crops.
True. Resistant individuals survive and reproduce, so the crop becomes less effective over time.
True or false? Genetically modified food has been proved to be harmful to human health.
False. There is no clear evidence of harm, but some people are concerned about long-term effects that are not yet known.
State one practical risk of using genetic engineering in agriculture.
Transferred genes may spread to wild plants or other crops by pollination, creating unwanted resistant weeds.