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Memoria inmunológica y otros aspectos del CRISPR
El sistema CRISPR-Cas actúa como un mecanismo de defensa bacteriano frente a elementos genéticos invasores como virus y plásmidos, y constituye la bas…
El sistema CRISPR-Cas protege a las bacterias de elementos genéticos extraños.
En los laboratorios, el sistema se programa utilizando Cas-9 para editar genes en plantas, animales y humanos.
Cas9, una endonucleasa de Streptococcus pyogenes, se introduce en las células con un ARN guía sintético: el ARNg.
El sgRNA guía a Cas9 a la secuencia del motivo adyacente del protoespaciador, lo que le permite unirse y cortar el ADN en el sitio objetivo.
Para la inserción del gen, Cas9, guiado por un sgRNA, escinde el sitio, lo que permite la recombinación homóloga para insertar el nuevo gen.
Para la deleción de genes, dos sgRNAs dirigen a Cas9 para cortar ambos extremos de la región diana.
El gen se extirpa y el sistema de reparación une los extremos cortados.
CRISPR-Cas9 ha sido diseñado para inactivar el VIH mediante la extirpación de su ADN de las células infectadas. Los sistemas de ingeniería como Csy4 se dirigen al ARN libre del VIH, aunque estos métodos aún son experimentales.
Además de dirigirse a un solo locus, CRISPR-Cas9 puede editar varios genes simultáneamente, como eliminar múltiples copias retrovirales.
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Q1: How does Cas9 identify and cut DNA at the target site?
Cas9, an endonuclease from Streptococcus pyogenes, uses a synthetic guide RNA (sgRNA) to locate specific DNA sequences. The sgRNA directs Cas9 to the Protospacer Adjacent Motif (PAM) sequence, typically 5'-NGG-3', allowing Cas9 to bind and introduce a double-stranded break at the precise target location.
Q2: What is the difference between gene insertion and gene deletion using CRISPR-Cas9?
Gene insertion uses one sgRNA to guide Cas9 to cleave a site, then homologous recombination inserts new genetic material. Gene deletion employs two sgRNAs directing Cas9 to cut both ends of a target region, excising the DNA fragment, which the cell's repair system then rejoins through non-homologous end joining.
Q3: How can CRISPR-Cas9 be used to treat HIV infections?
CRISPR-Cas9 has been designed to inactivate HIV by excising integrated viral DNA from infected cells. Additionally, engineered systems like Csy4 target free HIV RNA to degrade it, though these antiviral strategies remain experimental and represent emerging therapeutic approaches for combating viral infections.
Q4: What is the original function of the CRISPR-Cas system in bacteria?
The CRISPR-Cas system serves as a bacterial defense mechanism against invading genetic elements such as viruses and plasmids. Originally discovered in prokaryotes, the antiviral system of bacteria and archaea has been repurposed as a powerful genome-editing tool for laboratory applications across diverse organisms.
Q5: Can CRISPR-Cas9 edit multiple genes simultaneously?
Yes, CRISPR-Cas9 enables multiplexed genome editing, allowing simultaneous modification of multiple genes in a single organism. This capability is particularly advantageous in complex genetic studies and therapeutic applications, such as removing multiple retroviral copies from infected cells in one editing event.
Q6: What organisms can be edited using CRISPR-Cas9 technology?
CRISPR-Cas9 has been reprogrammed to modify the genomes of diverse organisms, including plants, animals, and humans. This versatility makes it a revolutionary tool for genetic engineering across a wide range of biological systems and research applications in both basic and applied science.
Q7: How does the synthetic guide RNA direct Cas9 to the correct DNA location?
The synthetic single guide RNA (sgRNA) contains a complementary sequence that guides Cas9 to a specific genomic locus adjacent to the Protospacer Adjacent Motif (PAM). This precise targeting ensures Cas9 binds and cuts only at the intended DNA location, enabling accurate and efficient genome editing with minimal off-target effects.