Selective breeding and genetic engineering · Year 12
For thousands of years people have bred plants and animals with the characteristics they want. Today scientists can also move a single gene from one organism into another, and can make clones. These techniques bring big benefits, but they also raise questions about safety and what is right.
Key facts
- Selective breeding: choose parents with the characteristic you want, breed them, choose the best offspring and breed them, and repeat over many generations. Examples are disease-resistant crops, cows that give more milk and gentle dogs.
- Selective breeding can lead to inbreeding: there is less variation, so the organisms are more likely to suffer from inherited defects and from new diseases.
- Genetic engineering changes an organism's genome by adding a gene from another organism. Bacteria have been given the human insulin gene, and crops have been given genes to resist insect pests or weedkillers or to make more vitamins.
- The steps: enzymes cut the gene out; it is inserted into a vector, such as a bacterial plasmid or a virus; the vector carries it into the target cells. In plants and animals the gene is put in at an early stage, so all the cells get it.
- Clones are genetically identical organisms. Plants are cloned by cuttings and tissue culture; animals by embryo transplants and adult cell cloning, which made Dolly the sheep in 1996.
- Concerns about GM organisms include genes spreading to wild plants, effects on insects and wild flowers, unknown long-term effects on health, and whether it is right to change genes.
- Gene therapy aims to treat inherited disorders by putting a working allele into a patient's cells.