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Lecture 4

CBIO 3400 Lecture Notes - Lecture 4: Crispr, Cas9, Base Pair

Cellular Biology
Course Code
CBIO 3400

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CBIO 3400
Exam 4 Lecture 4
Genome Editing and CRISPR/Cas9
Bacterial Adaptive Immune System: CRISPR-Cas9 Invader Immunity
CRISPR: Clustered Regularly Interspace Short Palindromic Repeat
It’s a type of bacterial adaptive immune strategy.
Certain regions in the genome that look strange Short palindromic sequences (repeat
regions scattered throughout the genome)
o This is how they protect themselves from invading pathogens they have to deal
CRISPR locus
o Repeat regions- Short palindromic sequences
Reads the same forward as it does backwards.
Palindromes (CGTT, GCAA), these things base pair with each other and
create hair pin structures which is important of the processing of CRISPR
Hair pin helps tell us where we want to cut the sequence
Palindromes help id the target regions for bacterial phages. Serve as book
ends to help separate the functional pieces
o In b/w repeat regions, there are spacers.
The different “spacer” regions correspond to foreign DNA elements
o Cas genes- Cas = CRISPR-Associated genes
Overview of the CRISPR-Cas9 Pathways
Bacteria phage inserts its genome into the bacteria.
Adjacent to PAM (protospacer adjacent motif)
o NGG is the PAM sequence for CRISPR-Cas9 nuclear machinery
o PAM are everywhere.
Cut out spacer region and put it in-between the repeated sequences
Transcribes RNA from this locus
o Makes CRISPR RNA which fit into the Cas machinery
Makes a cut in double stranded DNA
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