Lecture 8

Question 1

What are the two possible repair mechanisms in mammalian cells

Answer 1

Non-homologous and homologous recombination repair.

Question 2

What is the process of Non-homologous end joining

Answer 2

Inserts a double stranded break and remove overhanging.
Ends are synapsed and additional proteins are requited.
Nuclease activity removes overhanging nucleotides.
Trimmed ends are ligated= mutagenic

Question 3

How is the process of homologous recombination

Answer 3

Introducing site specific double strand break
- Produces endonuclease that recognises a specific site on the genome
- Recognised DNA sequence
- Proteins bind to the specific site in DNA

Question 4

What is the function of the CRISPR/Cas system

Answer 4

Allows direct targeting of RNA or DNA to interfere with viruses, plasmids, prophages or other incoming chromosomal sequences. Uses RNA guided destruction method.

Question 5

What are the properties of Cas genes

Answer 5

• 6 core conserved cas genes
• required for processing events
• encode proteins with functional domains associated with nucleic acid

Question 6

What is a protospacer and protospacer adjacent motif

Answer 6

A short DNA sequence that served as a binding site for the necessary endonuclease and processing machinery

Question 7

What is the relevance of the RNA hairpin in CRISPR/Cas

Answer 7

RNA hairpin of gRNA scaffold forms which allows Cas9 to bind. Cas9 digests target at a specific point