lec 2-3 methods and model organisms

Question 1

wavelengths of visible light (for light microscopy)

Answer 1

between 380 - 760nm

Question 2

frequency is inversely proportional to

Answer 2

wavelength

Question 3

darkfield microscopy

Answer 3

illuminates from the side so only scattered rays hit the lens

Question 4

white light

Answer 4

changes the phase of the wave depending on the density of the specimen

Question 5

absorption of photons

Answer 5

molecules absorb light photons at one wavelength and emit light a lower energy one

Question 6

GFP

Answer 6

tag protein

attaches to protein at -N r -C terminal

Question 7

benefits of GFP structure

Answer 7

barrel structure

creates channel for light to activate fluorophore inside

Question 8

Bimolecular Fluoroscence Complementation (BiFC)

Answer 8

used to determine if 2 proteins interact

each protein is tagged with half the fluorophore
if proteins do interact, the fluorophore will reconstitute
no light emitted then no protein interaction

Question 9

Fluorescence Recovery After Photobleaching (FRAP)

Answer 9

used to measure protein dynamics in cells

fluorescence lost after laser bleaches fluorophore
fluorescence recovery has to come from somewhere
measure time taken to reach almost maximum fluorescence after photo-bleaching

Question 10

if a protein cannot efficiently bind GTP..

Answer 10

.. it takes longer to recover the fluorescence in the ER membrane after photo-bleaching

Question 11

immunocytochemistry

Answer 11

used antibodies to visualise localisation of proteins

Question 12

limitation of immunocytochemistry

Answer 12

only useable on ‘fixed’ proteins (dead)

Question 13

resolution

Answer 13

minimum distance that separates two objects where they can still be seen as distinct

Question 14

NA

Answer 14

numerical aperture

Question 15

limit of resolution )light microscopy)

Answer 15

200nm

Question 16

limit of resolution (electron microscopy)

Answer 16

0.05nm

Question 17

transmission electron micorscopy

Answer 17

sample embedded in block of resin
diamond knife used to slice sheet of sample
multiple 3D photographs taken

Question 18

correlative microscopy

Answer 18

combines advantages of both light and electron microscopy

Question 19

x-ray crystallography

Answer 19

used to study atoms in greater detail

Question 20

model organism

Answer 20

non-human species used to study fundamental mechansims similar to those in more complex organisms

Question 21

problems with studying on humans

Answer 21

ethical
complex - 20,000 genes, many redundancies and introns
technical - expensive, inaccessible cells e.g. neurons

Question 22

redundancy genes

Answer 22

when 2 genes have the same function

Question 23

introns

Answer 23

non-coding genes

Question 24

examples of common model organisms

Answer 24

fly
mouse
worm
fish
yeast

Question 25

factors affecting choice of model

Answer 25

what do you want to find out?
complexicity of organism
techniques required 
cost/time
ethical considerations

Question 26

S.Pombe used to study mechanisms of cell shape

Answer 26

S.Pombe has a highle reproducible shape

mutants with extreme changes in length have cell cycle defects
mutants with extreme changes in polarity have actin/cell wall defects

Question 27

naked mole rat used to study mechanisms of ageing

Answer 27

rat is long lived for its size

has reduced incidence of cancer

Question 28

synthetic bacteria created

Answer 28

only 473 essential genes

Question 29

knock out (KO)

Answer 29

gene completely deleted, no protein

Question 30

knock down (KD)

Answer 30

gene partially degraded, some protein left

Question 31

mutant

Answer 31

gene is mutated, protein there but not fully functional

Question 32

conditional mutant

Answer 32

gene mutated but phenotype only shows under certain conditions

Question 33

genetic screening methods

Answer 33

mutagenesis of wildtype population
isolate mutant colonies
use genetic manipulation

Question 34

pros of S.Pombe as a model organism

Answer 34

cheap
ethical
easy
small genomes
non-pathogenic

Question 35

cons of S.Pombe as a model organism

Answer 35

not human
missing characterics of mammalian cells
has a cell wall