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CRISPR- A word processor for editing the genome - iBiology & Youreka Science - Contenido educativo

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Subido el 26 de diciembre de 2021 por Francisco J. M.

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Since the discovery of DNA's fundamental role in building and sustaining life, 00:00:15
scientists have dreamed of having the ability to easily edit DNA in very precise ways. 00:00:20
But why would they want to do this? 00:00:25
Well, making specific changes to DNA sequences can help scientists better understand the function of certain genes, 00:00:27
produce specific disease models, or even repair defective genes that cause diseases in humans. 00:00:34
This is an exciting prospect, but methods to try and do this weren't practical or rightly applicable. 00:00:40
However, a few years ago, a gift from biology came from the basic research of the bacteria immune system, 00:00:45
which gave scientists the ability to easily, customizably, and precisely edit genomes. 00:00:51
Bacteria evolved ingenious ways of protecting themselves against pathogens such as viruses 00:00:57
by using a system called CRISPR-Cas. 00:01:01
CRISPRs are stretches of DNA sequence found in the bacterial genome, 00:01:05
In close proximity to CRISPR are the Cas genes, which encode proteins necessary for the CRISPR system. 00:01:08
Up until a few years ago, what was known about the CRISPR-Cas system is that bacteria infected by a virus 00:01:16
incorporate elements of the virus's DNA into the CRISPR sequence. 00:01:22
This protected the bacteria from future infection by this virus. 00:01:27
Scientists observed that when a virus invades a bacterium, 00:01:31
the CRISPR DNA produces one or two small RNAs called CRRNA and tracer RNA. 00:01:35
These RNAs bound to Cas proteins and formed complexes that cut the DNA of the invading virus, 00:01:43
thus protecting the bacteria from infection. 00:01:50
But many questions still remained. 00:01:53
How did the small RNAs and Cas work together to detect and destroy viral DNA? 00:01:56
In 2012, a group of scientists made a major breakthrough and discovered not only how the CRISPR RNAs and Cas cut DNA, but also how to create a new technique to specifically change the DNA sequence of any organism with great ease. 00:02:01
This discovery came from a group of scientists led by Jennifer Dunna at UC Berkeley and Emmanuel Charpentier at Umeå University in Sweden. 00:02:20
They published their results in Science in an article titled 00:02:29
A Programmable Dual RNA-Guided DNA Endonuclease in Adaptive Bacterial Immunity. 00:02:33
So what exactly did these scientists find, and why is it so important for future biomedical research? 00:02:40
First, the scientists dissected how Cas9 and the two RNAs can cut DNA. 00:02:46
They found that the two RNAs, CRRNA here in red and tracer RNA here in green, pair up, 00:02:51
recruit Cas9 protein, and direct it to bind the target DNA via the complementary base pairing 00:02:58
between the red CRISPR RNA and the target DNA. 00:03:04
Once at the proper DNA site, Cas9 cleaves both DNA strands. 00:03:08
This cleavage occurs at a very specific and conserved position 00:03:12
that is dictated by the sequence in the red CRISPR RNA molecule. 00:03:16
This process is similar to finding your plane by matching the gate number to the one on your boarding pass. 00:03:21
The scientists then wondered if they could engineer one RNA molecule 00:03:29
that mimicked the structure of the CRISPR RNA and tracer RNAs bound together 00:03:33
that would guide Cas9 to cut DNA at a specific location. 00:03:38
The scientists designed one RNA molecule that consisted of the red and green RNA molecules 00:03:43
connected together by a hairpin structure. 00:03:49
In this case, they engineered the RNAs to target specific sequences of the gene 00:03:52
encoding the green fluorescent protein, GFP. They added the engineered RNA molecules to the GFP DNA 00:03:57
sequence along with the Cas9 protein and asked whether Cas9 would cut GFP DNA at specific 00:04:04
sequences. And it did. When the RNA molecules were designed to bind to different regions of the GFP 00:04:11
sequence, the GFP DNA sequence was cleaved at that specific location. On a gel that separates DNA 00:04:20
according to size, you can see distinctly sized fragments of the GFP DNA molecule, 00:04:30
resulting from having been cut in a specific location. This was huge as it meant that 00:04:36
scientists could engineer one RNA sequence, introduce Cas9, and cut DNA at a specific 00:04:41
location of their choice. By having this simple and easily programmable system, 00:04:48
scientists can now induce breaks in the DNA at precise locations. 00:04:54
When the cell tries to repair the broken DNA strands by ligating them back together, 00:04:58
it often causes a small insertion or deletion that changes the DNA sequence. 00:05:03
Scientists can take advantage of this process to add or remove specific DNA sequences at the site of the break. 00:05:09
We now have a DNA word processor that can be used to change genome sequences, 00:05:17
including our own. CRISPR has a bright future ahead to advance our understanding of human disease 00:05:23
by creating a tool from basic research that is now widely used in the fields of molecular biology 00:05:30
and genetics to change the genomes of any organism. But much work needs to be done to make the system 00:05:37
more reliable. Use of the CRISPR system to edit human embryos is also a controversial issue and 00:05:43
And researchers have already started the conversation about using this technology ethically and 00:05:50
safely to advance human knowledge. 00:05:55
This video has been provided to you by Eureka Science and iBiology, bringing the world's 00:06:01
best biology to you. 00:06:05
Subido por:
Francisco J. M.
Licencia:
Reconocimiento - No comercial - Compartir igual
Visualizaciones:
63
Fecha:
26 de diciembre de 2021 - 13:38
Visibilidad:
URL
Centro:
IES ALPAJÉS
Duración:
06′ 09″
Relación de aspecto:
1.78:1
Resolución:
1920x1080 píxeles
Tamaño:
86.87 MBytes

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