Cuttings

New plants can be grown quickly and cheaply by taking cuttings from older plants. All the new plants are genetically identical to the parent plant, so they will have exactly the same characteristics.

Cuttings produce roots very quickly if they are kept in warm, moist conditions.

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Artificial Selection

New varieties of plants and animals can be produced by artificial selection.

Farmers and plant growers choose individuals that have useful characteristics and breed from them. Plants may be bred for:

• Flavour
• Appearance
• Resistance to disease
• Size

Yield animals may be bred for:

• Type of flavour of meat
• Body size
• Rate of growth
• Milk production
• Appearance

Individuals from the first generation with the desired characteristics are cross-bred and this process of selection and breeding continues until all the offspring develop with the desired characteristics. This process of selective breeding can take several years to produce a new variety.

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Disadvantages of Selective Breeding

• Takes a long time to produce a new variety
• Reduces the number of different alleles in a population
• Cloning, for example, by taking cuttings, also reduces the number of alleles
• In the future, it may be harder to produce new varieties
• This may lead to problems in the survival of a species if they cannot evolve to cope with changed environmental conditions, e.g. a new disease could wipe them all out if they are identical
  

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Plant tissue culture

Small groups of cells from a plant that is healthy, disease-free and has the desired characteristics, are grown on sterile agar plates.
The agar contains all the necessary nutrients and hormones for growth.

Clusters of identical cells form as a result of mitosis. 

These can be split to produce many new plants, which are all identical clones.

Animal embryo transplants

An egg cell can be fertilised in a petri dish. It then develops into a ball of cells called an embryo.

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Genetic Engineering

Genetic engineering involves identifying a specific gene on a chromosome, cutting it out using enzymes and transferring it into a different organism to produce useful products.

Human genes are inserted into bacteria to produce human insulin for diabetics and human growth hormone for children who otherwise wouldn't grow properly.

Other drugs, such as vaccines and antibiotics, are produced in this way.

To produce the drugs in large quantities, the genetically-engineered bacteria are cultured on a large scale.

Genes can be transferred into animal embryos so they develop with the desired characteristics e.g. sheep and cows can produce hormones and drugs in their milk.

We are very close to a cure for some inherited diseases, by inserting healthy genes in the place of defective ones.

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