Genome Editing = CRISPR / Cas9

Question 1

What is genome editing?

Answer 1

DNA is inserted, deleted or replaced in the genome of an organism using nucleases

Question 2

What is the structure of the CRISPR locus?

Answer 2

•Transactivating RNA = sequence of RNA that is needed

•Operon of cas genes encoding Cas protein components (e.g. Cas1/Cas2/Cas9)

•Identical repeat array = sequences of bacterial genome

•Spacer of invading DNA

Question 3

What is the role of guide RNA (gRNA)?

Answer 3

enables selective binding of Cas9 to invading DNA sequences

Question 4

How does CRISPR act as an immune system in prokaryotes against invading DNA/RNA?

Answer 4

1.Invading DNA recognised and cut by Cas1-Cas2 protein complexes into fragments termed protospacers

2.Protospacers integrated into CRISPR locus located in the bacterial genome

Question 5

What is the role of the cas operon?

Answer 5

Cas operon = encodes cas proteins required for DNA cleavage