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Biology - Genetic Engineering (AQA Syllabus A)

Genetic variation and its control is one of the subjects looked at in GCSE Science. This is the last of four quizzes on the subject and it looks specifically at genetic engineering.

Humans have sought to control genes and to exploit genetic variation for thousands of years. Selective breeding has been used to modify the characteristics of plants and animals to better suit our needs. Examples are disease resistant plants, or cattle that give high yields of milk. But there are problems with this, since future generations of selectively bred organisms will share increasingly similar genes.

During the twentieth century, scientists began to understand genes and genetics more deeply than before. Knowledge has reached the point where it is now possible to identify a gene for a particular characteristic and transfer it artificially into an organism. This is called genetic engineering and it allows genes to be transferred from the same species or from different species.

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Some examples of genetic engineering are:

  • Adding the carotene gene from carrots into rice so that people lacking vitamin A in their normal diet can make it if they eat genetically modified (GM) rice.
  • Adding a gene from weedkiller resistant plants into soya beans. This means the farmer can spray their crop with weedkiller and only the weeds will die, meaning there is less competition and the yield of soya will be increased.
  • Adding the insulin gene from humans into bacteria, meaning that insulin can be produced rapidly and cheaply to treat diabetics.

There are many ethical issues surrounding human control of genes by genetic engineering, and plenty of health worries too. Since the science is new, no-one knows what the long trem effects on the health of people eating genetically modified (GM) crops or animals will be. There are also religious objections because it seems like scientists are 'playing God'. You need to make up your own mind after considering the facts from both sides carefully.

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  1. Mutations are changes to an organism's what?
    Whilst mutations can lead to changes in all three of the others, a mutation is a change to a gene which is part of the DNA
  2. Taking the pollen from one rose flower and using it to pollinate a flower on a different rose plant is an example of what?
    Cross-pollination of plants is a common form of selective breeding
  3. Which of the following is not a disadvantage of selective breeding?
    This is a disadvantage of genetic engineering rather than selective breeding
  4. How do scientists cut out a specific gene ready to place into another organism?
    The enzymes used to cut genes from DNA are called restriction enzymes
  5. What is the correct order of these steps which describe genetic modification?

    1. Isolation of the gene responsible for the characteristic.
    2. Replication of the transgenic organism.
    3. Selection of the desired characteristic.
    4. Insertion of the gene into another organism.
    A transgenic organism is one which has at least one gene from a different species added to its DNA. With questions like this, even when you don't know the answer you can often work it out using common sense
  6. Where in a cell are the genes found?
    The chromosomes are strings of genes and are found in the nucleus of cells
  7. These statements are about the role of enzymes in genetic modification. Which is correct?
    Were you paying attention to Q4? Ligase enzymes are used to join pieces of DNA together
  8. Which of the following can be used as vectors?
    Plasmids are small circular pieces of genetic material found in bacteria. Vectors are used to carry the new gene into a cell where it is to be added. It is unlikely, but possible, that this could be asked in the higher tier exam
  9. Nowadays, most insulin is made using genetically modified bacteria that have had the human gene for insulin inserted into them. Which of the following could be regarded as an advantage of GM insulin over natural insulin?
    Natural insulin is taken from the pancreases of pigs or cattle. Its supply is limited and it can cause adverse reactions in some people
  10. Which of the following is a moral objection to genetic engineering of a crop?
    The other three objctions are scientific. There are many more issues that need discussing and investigating before going ahead with GM cops or banning them altogether

Author: Kev Woodward

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