CRISPR – Clustered Regularly Interspaced Short Palindromic Repeats

Cas 9 – A Protein that cuts both strands of DNA. (like scissors!)

  • Cas 9 was an evolutionary advancement of bacteria to recognize and destroy foreign (viral) DNA.

We use it for targeted genome editing by introducing breaks in the DNA. CRISPR acts as like a search and edit tool – it can find damaged genes, cut it when it recognizes the sequence and delete it, insert something else, or edit individual bases.

How it works:

  1. Cas 9 can recognize any DNA sequence that the guide RNA tells it to. We can change the guide RNA in the Cas system to recognize any sequence we want.
  2. Cas 9 acts as a pair of molecular scissors that cuts DNA at a specific location (what guide RNA code we give it) so we can add or remove DNA.
  3. When the sequence is recognized, the cas protein cuts the DNA of the target and we can delete, edit, or add in anything we want!

As an analogy: we can use it as to search for a word in a document and replace it with out own word – like fixing a typo!

Benefits:
  1. Fastest, cheapest way to edit an organism.
  2. Can edit and manipulate a living organism (no need to grow GMO seeds in a lab and hope they pass the gene down!)
  3. Therapy: Can be used to recognize the sequence for a genetic disorder (ex. cystic fibrosis) and edit the gene to be the healthy allele (like fixing a typo in the genetic code!)

Editing the Germ Line: Therapy vs. Enhancement

CRISPR can (and has been used) to edit germ line cells.

  • Germ line editing is when the sperm, egg, or embryo is modified.

  • The embryo will continue to divide and all the cells in an organism will contain the edited DNA with whatever edit we made.

These changes can be passed down to all that individuals offspring – we have now altered the human genome in way that cannot be reverse

How it using CRISPR on the germ line different from any other cell?

 

  • Editing a somatic (regular body cell) will only affect that cell and the targeted area 
  • This trait cannot be passed onto offspring. The editing ends with the individual

Designer Babies:

Designer Babies – A baby whose genetic makeup has been selected or altered, often to include a particular gene or to remove genes associated with disease.

 

  • CRISPR can be used to edit traits that are unnecessary but can provide benefits. Things like perfect eyesight, hair colour, etc. This is enhancement – to improve an individual.
  • It can be used for genetic plastic surgery.

 

Response: Should we use CRISPR to start germ line editing out genetic diseases? Why or why not?