Genetic Engineering (AQA GCSE Biology): Revision Note

Genetic engineering: Basics

• Genetic engineering involves:

modifying the genome of an organism by introducing a gene from another organism

• This is carried out by 'cutting' the desired gene from a chromosome in one organism, and inserting it into the cells of another

• The resulting genetically modified (GM) organism will have new desired characteristics

Plant genetic engineering

• Genetically modified plant crops are crop varieties that have had DNA from other organisms inserted into their genome

• This is usually done to improve food production in some way, e.g:

  • tomatoes have been genetically modified to grow larger fruit

  • rice has been genetically modified to produce beta carotene (needed by humans to make vitamin A)

  • crop plants have been genetically modified to be resistant to diseases or resistant to certain herbicides

Bacteria genetic engineering

• Bacterial cells have been genetically engineered to produce useful substances

• E.g. the gene for human insulin has been inserted into bacteria, which then produce human insulin

  • This can be collected for medical use to treat people with diabetes

Advantages & disadvantages of genetic engineering

• There are a range of arguments for and against the use of genetic engineering in agriculture, particularly as relates to genetically modified (GM) crops

Advantages and disadvantages of GM crops

Advantages:

• GM crops can be resistant to insect pests; this reduces the need for chemical pesticides

• Resistance to herbicides allows farmers to spray chemical weed killers without harming their crops

• Increased yields allow farmers to feed more people and increase their income

Disadvantages:

• fears that GM crops might interbreed with wild plant species, introducing genes for pest or herbicide resistance into wild populations; this could:

  • kill non-target insects

  • reduce the usefulness of herbicide resistance

• concerns around increased herbicide use and its effects on wild flower species

• some people feel that the effects of eating GM crops on human health have not been fully explored

• companies that make GM seeds charge more for them, so they are not affordable for all farmers and poorer farmers cannot compete with larger farms

GM crops

• Crops that have had their genes modified are called genetically modified (GM) crops

• Crop plants have also been genetically modified to:

  • make them resistant to herbicides (chemicals that kill plants),

    • When the herbicide is sprayed on the crop field it only kills weeds and does not affect the crop itself

  • be drought-resistant

    • These crops are able to grow in dry conditions, increasing yield in dry regions

Curing diseases with genetic engineering

• Modern medical research is exploring the possibility of genetic modification to overcome some inherited disorders

• As these inherited genetic diseases are caused by faulty genes, it may be possible to treat these by inserting working versions of these genes into people with the genetic disease

• This is called gene therapy

The process of genetic engineering

Higher Tier Only

• The main steps in the process of genetic engineering:

  1. Enzymes are used to isolate (cut out) the required gene

  2. This gene is inserted into a vector

     • The vector is usually a bacterial plasmid (a piece of circular DNA found inside bacterial cells) or a virus

  3. The vector is used to insert the gene into the required cells of the target organism

     • Genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics