Bioinformatics Biotechnology

CRISPR

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CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. Repetitive DNA sequences, called CRISPR, were observed in bacteria with “spacer” DNA sequences in between the repeats that exactly match viral sequences.

CRISPR technology is a simple powerful tool for editing genomes. It allows researchers to easily change DNA sequences and modify gene function. Its many potential applications include correcting genetic defects, treating and preventing the spread of diseases and improving crops. However, it also has some ethical concerns.

CRISPRs are specialized stretches of DNA. The protein Cas9 or “CRISPR-associated” is an enzyme that acts like a pair of molecular scissors, able to cut the strands of DNA.

CRISPR technology was adapted from the natural defense mechanisms of bacteria and archaea. These organisms use CRISPR-derived RNA and various Cas proteins, including Cas9, to foil attacks by viruses and other foreign bodies. They do so primarily by chopping up and destroying the DNA of a foreign invader. When these components are transferred into other, more complex, organisms, it allows for the manipulation of genes, or “editing.”

Uses

  • CRISPR has made cheap and easy of editing some of the genomes of some plants and animals
  • It is used in scientific research
  • CRISPR technology also has the potential to transform medicine, enabling us to not only treat but also prevent many diseases
  • It is used it change the genomes of the children
  • It is used in fingerprinting cells and logging 
  • The key to CRISPR is the many flavors of “Cas” proteins present in bacteria, where they help defend against viruses. The Cas9 protein is the most widely used by scientists
  • CRISPR technology has also been used in the food and agricultural industries to engineer probiotic cultures and to vaccinate industrial cultures against viruses. It is also being used in crops to improve yield, drought tolerance and nutritional properties

Other CRISPR animal trials have ranged from genetically engineering long-haired goats for higher production of cashmere to breeding hornless cows to avoid the painful process of shearing horns off.

Compared to research involving animals, CRISPR trials that edit human DNA have moved more slowly, largely due to the ethical and regulatory issues at play.

Limitations

  • difficult to deliver the CRISPR/Cas material to mature cells in large numbers, which remains a problem for many clinical applications. 
  • 100% not efficient, so even the cells that take in CRISPR/Cas may not have genome editing activity.
  • 100% not accurate, and “off-target” edits, while rare, may have severe consequences, particularly in clinical applications.

Ethical issues

In addition to editing somatic cells, the editing of genomes of gametes (eggs and sperm) and early embryos also creates some ethical issues as  any such edits in humans would not only affect an individual but also his or her progeny. They could also theoretically be used to increase desirable traits instead of curing disease. Scientists have therefore called for a moratorium on human germline editing until the serious ethical and societal implications are more fully understood. 

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