Genetic analysis 3

Question 1

What is homologous recombination?

Answer 1

• Gene modification technique
• Exchange of genetic info between sequences similar in nature (DNA)
• If specific locus - forgein DNA must have identical DNA either side which is the same as the target DNA with the locus in the middle

Question 2

Advantages of CRISPR/cas 9

Answer 2

• Rapid
• Mutagenesis is efficient
• Specific
• Allows wide screens to be carried out

Question 3

What does UV radiation do to DNA?

Answer 3

• It causes thymines to covalently bond to each other, reducing the effects of DNA polymerase
• Causes insertions or deletions

Question 4

How does the Cas9/ CRISPR system work?

Answer 4

• Protects against viral genomes by capturing the genome, chopping it into small pieces and inserting the fragments into their its own genome
• The small fragments are transcribed and form hybrids with any other incoming virus, which targets them for destruction by cas9
• Addaptive immunity - many fragments for different viruses

Question 5

Advantages of homologous recombination?

Answer 5

Precise genome alterations, low frequency off-target

Question 6

What is cas 9?

Answer 6

An RNA guided DNA endonuclease

Question 7

How can scientists use CRISPR/cas9?

Answer 7

• Inject cas9 and CRISPR RNA (which matches the genetic sequence of the gene wanting to knock out/ edit) into organism
• Cas9 will make specific cleavage sites that is the same as the injected RNA
• This cleavage is repaired imperfectly, leading to a mutation
• Phenotype can be studied

Question 8

Disadvantages of zinc finger nucleases?

Answer 8

• Some off-target effects

- Size of deletion cannot be precisely controlled

Question 9

What is transgenesis?

Answer 9

Gene addition into a wild type organism

Question 10

What do x-rays and gamma rays do to DNA?

Answer 10

• Induces breaks (in the single or double strand)

- Can lose chromosome fragments

Question 11

Disadvantages of homologous recombination?

Answer 11

Slow and inefficient

Question 12

What is Fok1?

Answer 12

A zinc finger nuclease

Question 13

What is ‘linkage analysis’?

Answer 13

• Mapping genes to chromosomes

- Identifying position and location of the gene on chromosomes

Question 14

How are ‘molecular scissors’ made and what do they allow?

Answer 14

Made by attaching nuclease domain to a zinc finger domain

• Work in pairs
• Can create small deletions or gaps in DNA