Genetic Engineering + Cloning

Genetic Engineering

Vectors are things that are used to transfer DNA into a cell. There are two types: plasmids + viruses.

Plasmids: small, circular molecules of DNA that can be transferred between bacteria.

Viruses: insert DNA into the organisms they infect.

How genetic engineering works…

  1. The DNA you want to insert (e.g. the gene for human insulin) is cut out with a %%restriction enzyme%%. The vector DNA is then cut open using the same restriction enzyme.
  2. The vector DNA and the DNA you’re inserting are joined together with ligase enzymes to produce recombinant DNA.
  3. The recombinant DNA is inserted into other cells (e.g. bacteria).
  4. These cells can now use the gene you inserted to make the protein wanted (e.g. bacteria containing the gene for human insulin).

Transgenic: an organism containing genes transferred from another species.

Benefits to Genetic Engineering
  • Faster and more efficient way of getting the same results as selective breeding.
  • Improves crop yields/crop quality. This may help reduce hunger globally.
  • Introduces herbicide resistance, which leads to fewer 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.
  • Sterile insects could be created such as a mosquito. They would breed, which would lead to infertile offspring. This may help with spread of diseases, such as malaria, dengue fever and the Zika virus.
Risks of Genetic Engineering
  • Transfer of the selected gene into other species. What benefits one plant may harm another.
  • Some people believe it is not ethical to interfere with nature in this way.
  • GM crop seeds are often more expensive and so people in developing countries cannot afford them.
  • GM crops could be harmful, for example toxins from the crops have been detected in some people’s blood.
  • GM crops could cause allergic reactions in people.
  • Pollen produced by the plants could be toxic and harm insects that transfer it between plants.
Cloning - producing genetically identical organisms

Micropropagation - used to clone plants

  1. A plant with desirable characteristics is selected to be cloned.
  2. Explants (small pieces) are taken from the tip of the stems and the side shoots of the plant.
  3. The explants are sterilised to kill any microorganisms.
  4. The explants are grown in vitro (in a petri dish containing a nutrient medium with growth hormones in it).
  5. Cells in the explant divide and grow into a small plant.
  6. The small plants are taken out of the medium, planted in soil, and are put in greenhouses to develop into genetically identically plants with the desired characteristic.

 Cloning in Mammals - done by transplanting a cell nucleus

  1. Nucleus of an egg cell is removed from the mammal, creating a enucleated egg cell.
  2. Nucleus of an ordinary diploid body cell is removed and inserted into the enucleated egg cell.
  3. The cell is stimulated by an electric shock so it starts dividing by mitosis.
  4. The dividing cell is implanted into the uterus of another sheep to develop until it is born.
  5. The result is an animal that is genetically identical to the animal the diploid nucleus came from.