New Hope

 New Hope for Eliminating Hereditary Diseases

CRISPR is a new genome editing tool that allows scientists to change and correct specific genes with unprecedented precision, efficiency, and flexibility. It is far better than older techniques for gene splicing and editing. A genome is the total amount of genetic information in the chromosomes of an organism, including its genes and DNA sequences. In humans, a copy of the entire genome is contained in all cells that have a nucleus.

CRISPR is a naturally occurring process that scientists observed beginning in the 1980’s. It is an ancient defense mechanism found in a wide range of bacteria. Scientists noticed a strange pattern in some bacterial genomes. One DNA sequence would be repeated over and over again, with unique sequences in between the repeats. They called this odd configuration “clustered regularly interspaced short palindromic repeats”, or CRISPR.

Scientists realized the unique sequences in between the repeats matched the DNA of viruses that attack bacteria. CRISPR is one part of the bacteria’s immune system, which keeps bits of dangerous viruses around so it can recognize and defend against those viruses the next time they attack.

The second part of the defense mechanism is a set of enzymes called “Cas”(CRISPR associated proteins) which can precisely snip DNA. There are a number of Cas enzymes, but the best known is called Cas9. Together they form the CRISPR/Cas9 system. Cas9 is an enzyme that snips DNA and CRISPR is a collection of DNA sequences that tells Cas9 exactly where to snip. Scientists can give Cas9 the right sequence, called an RNA guide, and they can cut and paste bits of DNA sequence into the genome.

DNA is a very long string of four different bases: A, C, T, and G. Cas9 can recognize a sequence about 20 bases long, so it can be tailored to a specific gene. Scientists can repair a faulty gene by cutting it out with CRISPR/Cas9 and injecting a normal copy of it which replicates in each cell. The modified, corrected gene, can then be passed on to any offspring. CRISPR could one day hold the cure to any number of genetic diseases. Zhang, Sarah,