B15- Variation Flashcards
What is variation
Differences in the characteristics of individuals in a
population/species is called variation.
What is variation due to?
the genes the person has inherited (genetic causes)
The environment they live in/grew up in (environmental causes)
a combination of genes and the environment.
What are the steps in selective breading
1) Choose two parents with the desired characteristic (e.g. large muscle mass, blue flowers etc) from a mixed population.
2) Breed these two parents together.
3) From the offspring, choose the offspring with the desired characteristic and breed them together.
4) Repeat this process over many generations until all the offspring show the desired
characteristic.
What are the advantages of selective breeding
Can produce animals and plants with
desirable characteristics:
Increased milk/meat yield from cattle (which may increase profits for farmers)
Can create new varieties of (good) crops
Disease resistance in food crops or garden plants e.g. soya beans
Can produce domesticated animals with a gentle nature e.g. labradoodle
What are the disadvantages caused by selective breading
Selective breeding often results in a population of animals or plants with very similar genetics.
Selective breeding often involves breeding individuals that are closely related, known as inbreeding.
Inbred populations are more likely to suffer from genetic conditions caused by recessive alleles because they are more likely to inherit two copies of the recessive variants, one from each parent.
There they are more likely to be susceptible to diseases.
What is selective breeding
Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics.
What is genetic engineering
Genetic engineering is a process which involves:
modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
• An organism whose genes have been altered is called a ‘genetically modified organism’
Stages of genetic engineering (remember SIIR)
1) Select the required gene
2) Isolate the gene (using enzymes)
3) Insert this gene into another organism e.g. the plasmid of a bacterial cell. This is called the vector. Put the vector back into the host (e.g. bacterium)
4) Allow the genetically modified bacterium to reproduce.
5) Separate and purify the product of the gene.
What are the advantages of genetic engineering
GE is a faster and more efficient way of getting the same results as selective breeding.
Improve crop yields or crop quality, which is important in developing countries. This may help reduce hunger around the world.
Introduce herbicide resistance, which results in less herbicides being used, as weeds are quickly and selectively killed.
Insect and pest resistance can be developed and inserted into the plants. The plant produces toxins, which would discourage insects from eating the crop.
What are the disadvantages of genetic engineering
Possible harm when eaten by
humans/animals
Damage to food chains
GE crops could be harmful, for example toxins from the crops have been detected in some people’s blood.
Concerns that GM crops might affect the populations of wild flowers and insects,
