(1) Introduction to genetic engineering

Reminders: A chromosome as a thread-like structure of DNA, carrying genetic information in the form of genes.

A gene is a length of DNA that codes for a protein. An allele as a version of a gene.

Biotechnology example - bacteria:

Bacteria are useful in biotechnology and genetic engineering due to their rapid reproduction rate and their ability to make complex molecules.

It is not difficult to share their genetic code shared with all other organisms and the presence of plasmids.

Although bacteria are useful in biotechnology and genetic engineering there are concerns e.g. lack of ethical concerns over their manipulation and growth.

The basic idea of genetic engineering is to transfer a gene that gives rise to a desirable characteristic (trait) from one organism's genome to a different organism's genome, so that it acquires that desired characteristic.

• Know and understand in genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ using enzymes and transferred to cells of other organisms.

• Be able to demonstrate an understanding of the process of genetic engineering, including the removal of a gene from the DNA of one organism and the insertion of that gene into the DNA of another organism
  • This is exemplified by the production of insulin from bacteria by inserting the human insulin gene into bacteria and growing the bacteria to produce lots of insulin quickly and economically efficiently.

  • This amounts to changing the characteristics of an organism by changing its genes.

  • Useful genes from organism A can be inserted into organism B.

  • The desired useful gene (carrying desired characteristic) is cut out and isolated from the source organism A's chromosome by specific enzymes and inserted into a vector.

    • Restriction enzymes recognise specific sequences of DNA and cut the DNA at these points.

    • DNA ligase enzymes are employed to join the two pieces of DNA together at their 'reactive' ends.

    • The two different bits of DNA joined together are known as recombinant DNA.

    • A vector is something used to transfer DNA into the target cell e.g. a plasmid can be used to transfer DNA into a bacteria.

      • A plasmid is a relatively small ring of DNA.

      • They are found in bacteria and fungal yeasts.

    • The vector is usually a virus or a bacterial plasmid - a circular piece of DNA found in bacterial or yeast cells.

    • Plasmids are small circular molecular sections of DNA which can be transferred between bacteria.

    • When the vector is introduced to the target organism, the useful genes inserted into the cell.

  • Other enzymes are then used to remove an 'undesired' gene from organism B, the one you want to modify.

  • Then, via other enzymes, the desired transplanted gene can be inserted into organism B.

  • It is hoped one day to cure the genetic disorder cystic fibrosis with gene therapy ie replacing faulty genes with correctly functioning genes.

  • Viruses can have their genes modified to stop them being infective and use to make vaccines.

• Important note on cloning:

  • After plant or animal cells have been genetically modified, it is essential that they transfer the newly introduced genes.

  • Cells are first screened e.g. with an antibiotic, to kill cells that do not have the inserted gene.

  • The cells can then be successfully cloned.

  • This screening procedure is mentioned in the descriptions of insulin production and cloning plants.

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