Case unit 4

Question 1

what types of disease models are there

Answer 1

humans
animals
in vitro

Question 2

difference between cell dish and body

Answer 2

2D vs 3D 
cell vs cell contacts
complex signals 
matrix ridigity 
pO2 - normix conditons

Question 3

benefits of using mice

Answer 3

share a genome
mammals
small
fast breeding

Question 4

inbred mouse strains

Answer 4

several inbred mouse strains exist which mimic aspects of human disease
- NOD mouse (non obese diabetic)
- Lep ob/ob
do not necessarily reflect cause of human disease

Question 5

mutant mice

Answer 5

inbred
make target genes knock in/out
informed by genetic research

Question 6

how to make a mouse

Answer 6

breed mice to get germline mutations

modify embronic stem cell 
introduce blastocyst
inject into mother
breed chimeric offspring 
screen for germlin transmission 

knock outs/ knock ins

Question 7

knock outs

Answer 7

often performed to determine the physiological function of a gene

Question 8

knock ins

Answer 8

can introduce specific mutations

Question 9

limitations of mouse models

Answer 9

strains
timing - day/night cycle effect response
gender - men increase mice stress
cage - not challenged by normal environment
mice have different physiolgy to humans

Question 10

genetic screen

Answer 10

Think of a process e.g. cell division
Pick a model organism
Break every gene individually (chemical mutagen)
Does the process still work?
If not – identify the broken gene!

Question 11

advantages of screening

Answer 11

Quick
Simple genetics
Cheap 
Ethics free
Bias free

Question 12

CRISPR cas9

Answer 12

CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence.

Question 13

What are the to key molecules in CRIPSR

Answer 13

an enzyme called Cas9.

a piece of RNA called guide RNA (gRNA).

Question 14

what does cas9 do

Answer 14

acts as a pair of ‘molecular scissors’ that can cut the two strands of DNA at a specific location in the genome so that bits of DNA can then be added or removed.

Question 15

what does guide RNA do

Answer 15

consists of a small piece of pre-designed RNA sequence (about 20 bases long) located within a longer RNA scaffold. The scaffold part binds to DNA and the pre-designed sequence ‘guides’ Cas9 to the right part of the genome. This makes sure that the Cas9 enzyme cuts at the right point in the genome.

Question 16

how does CRIPSR work

Answer 16

The guide RNA is designed to find and bind to a specific sequence in the DNA.
gRNA has RNA bases that are complementary to those of the target DNA sequence in the genome.
guide RNA will only bind to the target sequence and no other regions of the genome.
Cas9 follows the guide RNA to the same location in the DNA sequence and makes a cut across both strands of the DNA.
At this stage the cell recognises that the DNA is damaged and tries to repair it.
Scientists can use the DNA repair machinery to introduce changes to one or more genes in the genome of a cell of interest.