3.7 first half Flashcards
what are the phases of the cell cycle?
- G1 phase (cells just hanging out)
-G0 (cellular state outside of the replicative cell cycle)
-S phase: replicate
-G2: get ready to divide
-M: mitosis –> cytokinesis
steps of mitosis
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
what happens in prophase?
- replicated chromosomes condense
- mitotic spindle assembles between 2 chromosomes
what happens in prometaphase?
-breakdown of nuclear envelope
- chromosomes attach to spindle microtubules
what happens in metaphase?
-chromosomes aligned at equator of spindle
what happens in anaphase?
paired chromatids separate to form 2 daughter chromosomes
what happens in telophase?
- daughter chromosomes arrive at poles of spindle
- formation of 2 nuclei
- assembly of contractile ring
what happens in cytokinesis?
cytoplasm is divided in two
what are the 3 types of cytoskeletal filaments?
- intermediate
- microtubules
- actin
________ filaments give the cell a semi-permanent shape against mechanical stress
intermediate
________ provide a track for intracellular transport, and are easily disassembled/assembled to fit transport needs of the cell
microtubules
_________ function in membrane mobility, cell movement, and temporary cell structure for when cell changes its shape
actin filaments
what is intermediate filament structure like?
8 tetramers twisted into a rope-like filament
_________ are filaments that support the nuclear envelope and must be broken down for the nuclear envelope to breakdown
Lamin IFs
how does the nuclear envelope breakdown and buildback up with the help of Lamins?
- lamins get phosphorylated
- filaments breakdown and take a little piece of the membrane with them
- they go and get pushed off to the side
- in telophase they get brought back and stick to/surround chromatids
- lamins de-phosphorylated
- pieces of envelope fuse back together
MTs form the _____ in prophase
mitotic spindle
MT are unidirectional and can only grow in the _____ direction
negative to positive
a temporary MT railroad is set up to do what?
so motor proteins can move cell bits to either side
how many types of tubulins are MT made of?
3 (all types of alpha/beta)
how do MT grow?
-dimers are kinked at first
-nucleotide exchange from GDP –> GTP
- when dimer has GTP it is no longer kinked and can be added to the growing polymerization
- GTP is removed, but since the dimers are stuck in the tubule they cant kink
what is the amount of kinking in the MT controlled by?
how quickly GTPase activity happens (less strained = easier to add subunits)
if the GTP < GDP what happens?
MT will unravel
If GTP>GDP what will happen?
addition proceeds faster than GTP hydrolysis
_______ allows the tubule to grow/shrink MT as needed
dynamic instability
what do microtubule associating proteins do (MAP?)
bind to free ends of MTs and stabilize ends selectively to polarize a cell
what are 2 examples of drugs that can change MT stability?
Colchicine, Taxol
how does Colchicine function?
binds to free tubulin to prevent polymerization, things cant add onto the end
how does Taxol function?
it prevents loss of subunits from MT
what are the 3 classes of MT that make the mitotic spindle?
astral, kinetochore, interpolar
________ attach to the kinetochore of condensed chromosomes and tethers them to poles. during anaphase when they shorten, they pull the chromatids apart
kinetochore MT
______ are any microtubule originating from the centrosome which does not connect to a kinetochore.
astral MT
________ are the antiparallel microtubules that originate from opposite poles, and overlap at the midzone of mitotic spindles.
interpolar MT
is a kinetochore actually attached to the end of the microtubule?
no! it has a yoke around it
_______ on interpolar MT push poles apart and pull chromatids across poles while _______ on astral MT pull poles toward membranes
kinesins
dyenins
