CRISPR AND THE ETHICAL DEBATE SURROUNDING IT
Cas9 is a type II system, Cas12a is a type V system and Cas13a is a type VI system.
There are 6 known systems but type I, II, and III have been studied extensively.
Cas9 is a type II system, Cas12a is a type V system and Cas13a is a type VI system.
All these systems are made up of two loci: a CRISPR locus and a Cas locus. A CRISPR locus is a library of small sequences which is obtained from previous viruses. Whilst a Cas locus is the one that codes for all the proteins that the system needs to work. When a cell is infected by a phage which is a prokaryotic virus, the invader can be detected by Cas proteins and the protospacer is integrated into the chromosomal CRISPR locus where it is called a spacer. For type I and II CRISPR-Cas systems, a single mutation can be all that is needed to escape immunity and because phages are fast evolving parasites, the escape from a spacer is usually fast.
The Difference Between Base and Prime Editing
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Base editing is a technology created to target single point mutations. For example, in our DNA the four base pairs that make up the specific sequence of our DNA are adenine with thymine and cytosine with guanine. Whenever any one of these base pairs cause a mutation that is they break that leads to them being dysfunctional. Base editing technology goes and tackles a single base pair one at a time.
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These small changes can silence a disease- causing gene or it can activate the necessary gene that will protect one from a certain disease. Base editors consist of 2 components joined together; a CRISPR Cas9 protein and a guide RNA which identifies features of a target DNA sequence.
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Prime editing on the other hand is a little different. If the original CRISPR technology is ofte compared with the analogy of scissors cutting up the specific location at the DNA, then prime editors are like word processors.
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They are capable of searching for precise DNA sequences and replacing them. Where the familiar CRISPR technique fully cleaves a strand of DNA in two, often creating some tiny, inadvertent genetic changes as byproducts, prime editing begins by slicing just one of the two strands of the double helix. The method is sleeker, less invasive, and offers the potential for precision genetic editing.The cut-and-repair mechanism is where prime editing really differs. Every prime editor (PE) contains multiple enzymes fused into one long, multipurpose piece of RNA. After the prime editor hones in on the genetic target, it makes a cut in one strand—not two—of DNA.
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Insertions and deletions within gene editing are called indels.
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In October 2016, a lung cancer patient in China became the first of 10 people in the world to receive an injection of cells that had been modified using CRISPR, the journal Nature reported.
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Duchenne muscular dystrophy is a debilitating condition that develops because of a mutation in a single gene, called the dystrophin gene, which is one of the longest genes in the body.
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One of the most common causes of childhood blindness is a condition called Leber congenital amaurosis, which affects about 2 to 3 per 100,000 newborns, according to the National Institutes of Health. The condition is inherited and is caused by mutations in at least 14 genes that are responsible for normal vision.
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Just as CRISPR can be used to modify the genomes of humans and animals, it can be used to modify the genomes of plants. Scientists are investigating ways to harness the tool's gene-editing ability to reduce disease in some crops and make others more robust.