1: L4-5 Flashcards
What ‘shines’ on a light micrscope
combined or specific light wavelengths
What ‘shines’ on a electron micrscope
electrons
What does microscopy begin with
What ‘shines’ on a light micrscope
what are 2 methods for fixation of cells
- Physical + solvents- strip out water
* Chemical- Formation of chemical cross links
2 ways to section tissue before immunostaining
Cryostat
Parafin
what is a confocal microscopy compared to flourescence
- Fluorescence method to get rid of out of focus light (a disadvantage of fluoresces= light above and below focal plain)
- Uses pinholes to prevent unwanted wavelengths
what are the 2 types of electron microscope + what measure
• 2 type: transmission (TEM) (what got blocked) and surface (SEM) (bounced off surface of sample // surface contours)
Can electron or fluorescent be conducted on living cells
Flor= on living cells electron= in vacuum
name the cell cycle phases
- Interphase (G1, S, G2)
2. Mitosis (prophase, metaphase, anaphase, telophase)
describe G1 phase and S phase
G1 phase (gap phase 1) - growth & normal - cellular activity S phase (synthetic phase) -DNA replication - 6-8 hours
2 ways cells die
- accidental
- programmed cell death (apoptosis) (occurs if the cell is abnormal in some way eg dividing too rapidly or infected by virus)
what processes is cell proliferations needed for
development and homeostasis
what is asymmetric mitosis
allows the stem cell population to replenish itself too
why is G1 not a fixed duration but the other phases are
variable as cell cycle can enter optional G0 resting phase
• Some cells, rapidly dividing (eg embryo) have no G0 phase
• Some differentiated cells are in G0 for remainder of their natural lives
what cell cycles do stem cells fluctuate between
G0 and cell-division cycle
what cues do most cells have/turn off
C. Most cells= signals to survive but no proliferation, no growth but also not dying = does not progress through cell cycle
what cues do cancer cells have/turn off
D. Cancer cell ignore or not receive death or growth inhibition cues, will make own proliferation and survival cues
What factors control cell cycle checkpoint transitions
A. Cyclin proteins accumulate at different stages
B. Cyclins combine w/ CDKs (cyclin dependant kinases) @ G2 > MPF = enable checkpoints to be passed
how do molecules move through the nucleus
must pass through nuclear pores
• Passive diffusion for small molecules <20-30 kilodaltons i.e. RNA
• Large protein have nuclear ‘export’ and ‘import’ signals
• Cargoes bigger than pores > partly unfolded to allow entrance
what is a territory of nucleus
• The defined location of each chromosome in the nucleus = it’s territory
• Territories: periphery (on lamina) or others at the centre,
o This can change with cell type, or shape
Describe FISH
- Short fragments of DNA that complement your sequence of interest + hybridises with them
- Add flourescent molecule
Where are large/small chromosomes typically for mammalian cells
o larger chromosomes tend to be at the periphery, smaller - centre
where are nuclear bodies and 3 examples
in space between the territories (interchromatin spaces/territories)
o i.e. nucleospeckle, paraspeckle, nucleolus
what do nuclear bodies do
- Nuclear body role: make the processing of RNA more efficient + DNA repair
what is the densest part of cell
nucleolus
what does the nucleolus do
• Site of ribosome production (ribosomal RNA)
what is paraspeckles built around
long noncoding rna NEAT1
What do paraspeckles do
• Regulate gene expression by sequestration (‘trapping’) of paraspeckle proteins including transcription factors - stops them from doing things, alters regulation of genes when cell becomes stress
how to measure movement rate of molecules in living cell
• Using a fluorescent protein fusion> photodynamics:
- Bleach the protein (turn black)
- Image the recovery of fluorescence
- Bleach recovery speed = how fast moving
why are nuclear bodies in centre
chromatin moves from periphery to centre to be transcriped // nuclear bodies there so they can aid in this process in appropriate location
