1: L2-3

Question 1

Define genome editing and its requirements

Answer 1

forces changes to the sequence of DNA in a controllable manner. In living cells, efficiently and permanently

Question 2

2 Historical version of Genome editing and their problems

Answer 2

1. Selective breeding
   - Relies on 1. Natural variants or 2. Random mutations
2. Designer DNA binding proteins
   - Problem: A new protein needs to be designed and made for each new DNA target site = $$ and time

Question 3

What does CRISPR stand for

Answer 3

Clustered Regularly Interspaced Short Palindromic Repeats

Question 4

How does CRISPR work

Answer 4

a. Cas9 is paired with an artificially created short guide RNA (gRNA, a molecular strand complimentary to a precise, disease-causing mutated section of DNA)
b. gRNA guides Cas9 to its corresponding section of the genome and induces a break in both DNA strands (DSBs), a ‘cut’.

Question 5

Advantages of CRISPR

Answer 5

Multi-cut= multi gene editing

easier than making 3d protein

Question 6

How does DNA repair itself in CRISPR

Answer 6

1. Non homologous end joining

2. homologous recom

Question 7

How does homologous recombination work

Answer 7

sister chromatin used as template for missing DNA sequence - CAS9 + rna + template sent

Question 8

3 applications of CRISPR

Answer 8

1. Add new sequence= homologous
2. modify existing sequence (point mutation example)= homologous
3. delete DNA = non homologous

Question 9

what’s a gene drive

Answer 9

o Used for population control of pests

- introduces suicide gene that’s passed on or one that eradicates fertility

Question 10

Limits of CRISPR

Answer 10

‘off target’ cutting
PAM site limits the choice of DNA sites to be cut
Cas9= large protein (hard to fit in virus)

Question 11

how to harness the repair mechanism of cell -carry out genome editing

Answer 11

-
When adding new seuqence to DNA
= Harness the ‘homologous recombination’ mode of DNA repair
- Break at point of new sequence, artificially introduce small piece of DNA used as template of repair
- Either side of DNA wanting to repair= high amount of homology (similarity)= trick to prompt central foreign DNA into genome

Question 12

Describe the nuclear envelope

Answer 12

• double-membrane: inner and outer membrane
• outer membrane = continuous with Rough ER
• nuclear pores = allows entrance and exit of molecules

Question 13

describe protein synthesis and transport

Answer 13

a. Gene prescribed onto mRNA in nucleus,
b. Translated into proteins in RER via nuclear pores
c. Moved to Golgi apparatus for sorting packaging and modifying
d. If protein to be moved outside of cell= transport vehicles or lysosomes

Question 14

Describe the features and function of the RER

Answer 14

• Cisternae/lamellae (sheets)
• Studded with ribosomes (protein/RNA subunits)
• Site of Protein synthesis

Question 15

Describe the features and function of the SER

Answer 15

• Tubular network
• Steroid + cholesterol synthesis
• Drug metabolism

Question 16

What does the geologic apparatus do

Answer 16

• Sorts, modify or package the protein

Question 17

how is the golgi similar/different to RER

Answer 17

• Similar to RER as both have sheet like structures

* Golgi Difference= bulging ends

Question 18

What are lysosomes and what do they do

Answer 18

• Lysosome created by golgi

* Digests unwanted molecules and ‘Recycles’

Question 19

3 ways molecules move across cell

Answer 19

diffusion
facilitated diffusion
active transport

Question 20

describe diffusion

Answer 20

• Lipid- soluable solutes (can pass freely through phospholipid membrane
• E.g. steroid hormones, gases (O2, CO2)
• Passive transport (no extra energy) - driven by concentration gradient

Question 21

describe facilitated diffusion

Answer 21

• Channel or carrier protein- mediated
• Too large or lipid insoluble i.e. glucose (uses glucose transporters)
• Passive transport (no extra energy) - driven by concentration gradient

Question 22

explain saturability of facilitated diffusion

Answer 22

• Saturable: only x amount of carrier proteins // if high concentration outside cell, but only few carrier proteins // limited rate of entry + saturation
o Can increase carrier proteins
• i.e. insulin triggers uptake of glucose transporters in membrane in cells then internalised after uptake complete = regulation of function

Question 23

describe active transport

Answer 23

• Carrier-mediated
• Energy required (from ATP)
• Enables transport AGAINST a concentration gradient
• eg: amino acids (builds proteins // needs large amount), ions (sodium-potassium pump)

Question 24

• Three main types of Integral membrane proteins

Answer 24

(1) Channels: not change conformation when molecules pass through, open and shut, passive
(2) Carriers: change of conformation when molecule passes through, Active OR passive transport
(3) Receptors: required for CELL SIGNALLING

Question 25

2 types of hormones and what they bind to on membrane (+ examples)

Answer 25

• Steroid hormones bind intracellular (inside cell) receptors Eg. Estrogen, testosterone, cortisol
• Peptide hormones bind membrane receptors, docked in membrane + are ligands Eg. Oxytocin, insulin, growth hormone