4b Flashcards
CRISPR-Cas9
CRISPR, a naturally occurring DNA sequence in bacteria, serves as their immune defense against viruses, and in genetic engineering, the CRISPR Cas9 technique utilizes a protein, Cas9, to recognize a sequence of DNA and cut it
whatis CRISPR used for
in: Research, dealing with disease, agriculture
what can CRISPR used to do in regards to genes
Can be used to insert, alter or remove genes from a genome
CRISPR-Cas9 ufnction in bacteria
In bacteria, it plays a role defending against viral infections (bacteriophages
Steps involved in fighting the virus using CRISPR Cas9
exposure:
1. Virus injects genetic information into the bacterial cell, thereofre virus infects bacteria.
- Bacteria recognises this as foreign
Enzymes (Cas1 and Cas 2) cut out short sections of the viral DNA known as a protospacer
3.The protospacer is introduced to the bacterium’s CRISPR gene to become a spacer
expression:
4. Virus injects genetic information into the bacteria.
- The CRISPR spacers are transcribed and converted into an RNA molecule known as gRNA (guide RNA)
- gRNA binds to Cas9 (enzyme) to create a CRISPR-Cas9 Complex
extermination:
7. The CRISPR-Cas9 complex then scans the cell for virus particles with complementary DNA to the gRNA.
8.If complementary, Cas9 cleaves the phosphate sugar backbone to inactivate the virus.
why is viral genetic information stored
Viral genetic information is stored so the next time the bacterial cell encounters the virus, the genetic information can be transcribed into Cas9
Cas9 is complementary and what does this mean
Cas9 is complementary to the viral DNA so it only destroys the virus, and not the bacteria.
How to use CRISPR Cas9 for gene editing
- Synthetic guide RNA (sgRNA) complementary to target DNA is produced
2.Cas9 enzyme obtained
3.Cas9 and sgRNA is added together to form a CRISPR-Cas9 complex
4.Complex is injected into a cell e.g. zygote
5.Cas9 finds the target DNA
6.Cas9 cuts the sequence of DNA.
7.DNA blunt end cut is made.
8.When cut, the DNA will repair by adding new nucleotides introduced by the scientist
compare genetic editing naturally and artfically
Purpose of genetic editing to attack and destroy invading viral DNA in naturally in prokaryotes whilst the purpose, whilst the purpose of artificially genetic editing is to induce mutations to alter genomic DNA.
In gene editing, gRNA is produced naturally in prokayotes throgh transcription and post transcriptional modifications of the CRISPR gene. But is produced artifically in a labrtorty
In Genetic editing naturally, pam sequence is specific to a host organism but in artifcal genetic editing, in the pam sequence the cas 9 enzyme can be altered to suit a specific gene.
Genetic editing nautrlaly in prokaryotes- after the cut DNA repair mechanisms often induce a mutation that inhibits a viral function, but in artifical gene editing, after the cut dna can mutate to knock out, enhance or otherwise change the
Limitations of CRISPR-Cas9
- Informed consent - Using embryos to alter an individual’s genome
Illegal to implant genetically modified embryos into human females - Safety with use of CRISPR-Cas9 as it may edit the wrong gene
Inequality in treating disease.
3.Only those who are able to afford this treatment
- Discrimination against
those treated and judged by society.
5.Removal of certain genes decreases genetic diversity
CRSPIR is made out of
spaces where the virus DNA enter and repeats where
gRNA
guide RNA which is trancirbed and forms a complex with the cap 9 enzyme, when person gets infected by the virus again
PAM sequence
protospacer ajacent motif,s a short DNA sequence (usually 2-6 base pairs in length) that follows the DNA region targeted for cleavage by the CRISPR system, such as CRISPR-Cas9
how are viral proteins and viral nucleic acids produced
When a virus infects a bacterial cell, viral DNA/RNA is inserted which then causes the bacterial cell to make viral proteins and nucleic acids.
What does an infection do to cells
The infection causes the bacterium to lyse and die, spreading viral particles to other cells.
