![]() ![]() For a long time geneticists used chemicals or radiation to cause mutations.If you can create a change in a gene, either in a cell line or a whole organism, it is possible to then study the effect of that change to understand what the function of that gene is.Over the years scientists have learned about genetics and gene function by studying the effects of changes in DNA.What other techniques are there for altering genes? Scientists adapted this system so that it could be used in other cells from animals, including mice and humans.Using CRISPR the bacteria snip out parts of the virus DNA and keep a bit of it behind to help them recognise and defend against the virus next time it attacks.Some bacteria have a similar, built-in, gene editing system to the CRISPR-Cas9 system that they use to respond to invading pathogens like viruses, much like an immune system.Scientists can use the DNA repair machinery to introduce changes to one or more genes in the genome of a cell of interest.ĭiagram showing how the CRISPR-Cas9 editing tool works.At this stage the cell recognises that the DNA is damaged and tries to repair it.The Cas9 follows the guide RNA to the same location in the DNA sequence and makes a cut across both strands of the DNA.This means that, at least in theory, the guide RNA will only bind to the target sequence and no other regions of the genome. The guide RNA has RNA bases that are complementary to those of the target DNA sequence in the genome. The guide RNA is designed to find and bind to a specific sequence in the DNA.This makes sure that the Cas9 enzyme cuts at the right point in the genome. The scaffold part binds to DNA and the pre-designed sequence ‘guides’ Cas9 to the right part of the genome. This consists of a small piece of pre-designed RNA sequence (about 20 bases long) located within a longer RNA scaffold. a piece of RNA called guide RNA (gRNA).This acts as a pair of ‘molecular scissors’ that can cut the two strands of DNA at a specific location in the genome so that bits of DNA can then be added or removed. The CRISPR-Cas9 system consists of two key molecules that introduce a change ( mutation) into the DNA.It is currently the simplest, most versatile and precise method of genetic manipulation and is therefore causing a buzz in the science world. ![]() CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence. ![]()
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