Gene Editing (CIE A Level Biology)

• Gene, or genome, editing allows genetic engineers to alter the DNA of organisms by inserting, deleting or replacing DNA at specific sites in the genome known to cause disease.
  • It differs from genetic engineering in that it involves modification of the existing DNA of an organism rather than the insertion of DNA from another organism.
  • Note that the term 'genome' refers to all of the DNA, or genetic information, found inside a cell.
• Gene editing enables the scientists to be more accurate in their manipulation of the genome
• Older gene editing techniques include
  • Modifying viruses to insert DNA, e.g. into the gene causing a disease
    • This sometimes resulted in DNA being inserted into other genes causing unforeseen consequences
  • Liposomes (small spheres of lipid molecules) containing the normal version of a gene being sprayed into noses
    • This was only a short-term solution as the epithelial cells lining the nasal passageway were short lived
• Today scientists have developed new gene editing techniques, the most commonly used one being CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)
  • This technique involves using the natural defense mechanism bacteria (and some archaea) have evolved to cut the DNA strands at a specific point as determined by a guide RNA attached to an enzyme (Cas9)
  • Once cut scientists can then either insert, delete or replace faulty DNA with normal DNA
• Gene editing is involved in gene therapies (e.g. developing treatments for cystic fibrosis and sickle cell anaemia).
  • Gene therapy is the treatment of a genetic disease by altering the person’s genotype
• As scientists learn more about the human genome (from the Human Genome Project) and the proteome, and have the technology to process large quantities of data through computational biology, they can gain a better understanding of which genes are responsible for genetic diseases and where they are located,and therefore what base changes need to occur to treat or cure the disease

CRISPR is one of the tools scientists can use to edit genes