Question

<Problem Set 9a Question 4 4 of 5 > Part A - TUA: Uverview UUR HIDRL yur g pruun When scientists use CRISPR-Cas9 to make specific cuts to a genome, they have a goal they're trying to achieve. Ohen, they either want to modify the protein that a particular gene encodes, or they want to block production of a particular protein. Depending on the goal, they customize the SANA they insert into the cell. For the CRISPR-Cas9 system to modify a eukaryotic genome, several steps need to happen. First, researchers must insert Cas9 and RNA into the desired cells. This can be accomplished through several techniques. For example, plasmid expression vectors encoding the components can be introduced into cells, or RNA and Cas9 protein can be directly injected into cells. Because eukaryotic cells have a nucleus, researchers add nuclear localization signals to Case, which help its protein translocate to the nucleus. When the sg RNA is also transcribed, it can guide Case to leave the target site in the cell's DNA The resulting double-stranded DNA break can be repaired by one of two mechanisms, which we'll discuss in the next part. It is during this DNA break-repair step that the genome is edited, with new bases sometimes being inserted or deleted, resulting in a modification from the original sequence. After repair of the break is complete, future transcription and translation of the repaired sequence will include any modifications introduced during the repair process The following figure shows the general steps that occur when a researcher uses the CRISPR-Cas9 system to modify a protein-encoding gene in eukaryotic cell with the goal of modifying the protein product. Drag the descriptions of the steps to their appropriate locations on the figure. Reset -ies The gone The moded DNA Create plasmid The RAIS translated into a modified protein The Cau protein cleaves the target sequence nachinery of the cell produces the Cas9 protein and the SANA The Cas9 protein guided by SORNA binds to its target sequence in the DONA roduce the Vectorio eukaryote cell During the process of DNA breaker the target sequence may be modified RNA Cas and RNA NRNA estression plasmid Next • Previous

Answer 1

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.

How does it work?
The CRISPR-Cas9 system consists of two key molecules that introduce a change into the DNA. These are:
an enzyme -called Cas9. 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.
a piece of RNA- called guide RNA (gRNA). This consists of a small piece of pre-designed RNA sequence (about 20 bases long) located within a longer RNA scaffold. The scaffold part binds to DNA and the pre-designed sequence ‘guides’ Cas9 to the right part of the genome. This makes sure that the Cas9 enzyme cuts at the right point in the genome.
The guide RNA is designed to find and bind to a specific sequence in the DNA. The guide RNA has RNA bases that are complementary to those of the target DNA sequence in the genome. 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 Cas9 follows the guide RNA to the same location in the DNA sequence and makes a cut across both strands of the DNA.
At this stage the cell  recognises that the DNA is damaged and tries to repair it.
Scientists can use the DNA repair machinery to introduce changes to one or more genes in the genome of a cell of interest.