How selective breeding works and the problem with it, the stages of genetic engineering, tissue culture and cloning, and the arguments around GM crops.
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1.What is selective breeding?
When humans choose organisms with a desired characteristic and breed them together, repeating over many generations.
2.Give the stages of selective breeding.
Choose parents with the desired characteristic, breed them, select the offspring showing it best, and repeat over many generations.
3.How long has selective breeding been going on?
Thousands of years, since humans first began farming.
4.Give four characteristics that are selectively bred for.
Disease resistance in food crops, animals that produce more meat or milk, domestic dogs with a gentle nature, and large or unusual flowers.
5.What is the main problem with selective breeding?
It reduces the number of different alleles in the population, so there is less variation. This is called inbreeding.
6.Why is inbreeding a risk?
The population is more likely to inherit disease or inherited defects, and less able to cope if conditions change.
7.What is genetic engineering?
Modifying the genome of an organism by transferring a gene from another organism, so it develops a desired characteristic.
8.Describe the stages of genetic engineering.
Enzymes cut out the required gene, the gene is inserted into a vector such as a plasmid or a virus, and the vector inserts the gene into the cells of the target organism.
9.What is a vector in genetic engineering?
Something used to carry the gene into the target cell, usually a bacterial plasmid or a virus.
10.Why is the gene transferred at an early stage of development?
So that the organism develops with the desired characteristic in all of its cells.
11.Give an example of genetic engineering in medicine.
Bacteria have been genetically engineered to produce human insulin for treating diabetes.
12.Give two examples of genetically modified crops.
Crops resistant to insect attack or to herbicides, and golden rice engineered to contain more vitamin A.
13.What is the main advantage of GM crops?
They give much larger yields, which could help feed a growing population.
14.Give three concerns about GM crops.
Effects on populations of wild flowers and insects, uncertainty about long term effects on human health, and concern about the spread of modified genes to wild plants.
15.What is the difference between selective breeding and genetic engineering?
Selective breeding works over many generations using genes already in the species. Genetic engineering directly transfers a gene, and can move genes between different species.
16.What is tissue culture?
Using small groups of cells from a plant to grow identical new plants.
17.Why is tissue culture useful?
It preserves rare plant species and lets nurseries produce large numbers of identical plants quickly.
18.What are cuttings?
An older, simple method where a branch of a parent plant is cut and planted, producing genetically identical clones.
19.What is embryo transplant cloning?
Splitting apart the cells of a developing animal embryo before they specialise, then transplanting the identical embryos into host mothers.
20.Describe adult cell cloning.
The nucleus is removed from an unfertilised egg, the nucleus from an adult body cell is inserted, an electric shock makes it divide to form an embryo, and the embryo is inserted into the womb of an adult female.
21.What is the offspring of adult cell cloning genetically?
Identical to the adult that supplied the body cell nucleus.
22.Give a concern about cloning animals.
It reduces variation in the population, there are worries about the health and lifespan of clones, and some object to it on ethical grounds.
23.Why might a farmer want to clone an animal?
To produce many copies of an animal with a valuable characteristic such as high milk yield.
24.What could gene technology do for inherited disorders in future?
It may become possible to overcome some inherited disorders by inserting a working copy of the faulty gene.
25.Why do some people object to genetic modification in principle?
They have ethical or religious objections to changing the genome of an organism, regardless of the outcome.
26.Why is it difficult to be certain GM food is safe?
Long term effects can only be judged over a long time, and it is hard to separate any effect from all the other factors in a person's diet.
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