Module 1—The Cell Cycle Flashcards
prokaryotic DNA vs eukaryotic DNA
ProkaryotesEukaryotes
- not bound to protein
- circular
- usually no introns
- bound to proteins
- linear
- introns
prokaryotic organelles vs eukaryotic organelles
ProkaryotesEukaryotes
- no membrane-bound organelles
- no nucleus
- 70S ribosomes
- membrane-bound
- nucleus
- 80S ribosomes
prokaryotic reproduction vs eukaryotic reproduction
ProkaryotesEukaryotes
- binary fission
- single haploid chromosome
- mitosis
- meiosis
prokaryotic size vs eukaryotic size
ProkaryotesEukaryotes
* 1-5 μm
- 10-100 μm
3 functions of cell division
- Reproduction
- Growth & development
- Repair & renewal
division produces ______ growth in cell number
exponential
phase in which most adult cells live
G0 or prolonged G1
cell cycle
life of a cell from formation to its own division
DNA is composed of 2 ___________ strands around an imaginary axis, forming a _________
polynucleotide
double helix
direction of polynucleotide strands
antiparallel to one another
5’ and 3’ ends of each
base pairs are situated _______ to helix axis
orthogonally
genome
all DNA in a cell
responsible for production of gametes
germline cells
“spools” for DNA
histones
DNA wrapped around one histone
nucleosome
octamer
8 core histones forming a spool
____ base pairs in a nucleosome
___ base pairs not around a histone
150
20
octamer includes 2 copies of 4 types of histones:
H2A
H2B
H3
H4
function of H1 histones
guide and organize nucleosomes
what do histone tails interact with?
what do they determine?
how is this significant?
nonhistone proteins and other octamers
density of the “wrapping” of the nucleosome
density determines whether genes are “on” or “off”
proteins involved with condensed nucleosomes
condensins
how is DNA condensed during mitosis?
bound into higher order loops by intense cross-linking
basic structure of chromatin
collection of nucleosomes = 30nm fibers
DNA is replicated in ___ phase, in the _______ state
S
chromatin
after copying of DNA, the ________ are formed from the original chromosome and its copy
sister chromatids
how are sister chromatids jointed?
cohesins join them all along their length
they are joined at the centromere most closely
constituents of centromere
repetitive sequences in DNA, mediated by proteins which recognize and bind to centromeric DNA
phases of the cell cycle
- Interphase
- G1
- S
- G2
- Mitotic phase
- Prophase
- Prometaphase
- Metaphse
- Anaphase
- Telophase
- Cytokinesis
events of G1
↑ metabolism, organelles, resources
events of S phase
growth & duplication of chromosomes
most dangerous phase for cell
why?
S phase
proteins cannot be synthesized from DNA undergoing replication
events of G2
growth & more duplication
centrosome duplicates (each has 2 centrioles)
↑ proteins necessary for mitosis
part of spindle that isn’t really necessary, and not found in plants
centrioles
events of prophase (5)
chromatids condense into chromosomes, with sister chromatids adhering to one another
nucleoli disappear
early mitotic spindle forms from centrosomes
aster is present
centrosomes move apart, pushed by lengthening microtubules
events of prometaphase (5)
begins with centrosomes on opposite poles, beginning to elongate cell
nuclear envelope fragments
kinetochore proteins forms on the centromeric DNA of each chromatid
mitotic spindle attaches to sister chromatids at kinetochore and begins to pull them back and forth
nonkinetochore tubules interact with those from the opposite pole, lengthening the cell
events of metaphase (2)
it is the beginning of…
chromosomes align on metaphase plate on cell equator
tension on chromatids is equal in both directions
beginning of the end of mitosis
events of anaphase (5)
Anaphase Promoting Complex (APC/C) frees separase from securin proteins
cohesin proteins are cleaved by separase
2 liberated daughter chromosomes are pulled apart toward opposite poles
nonkinetochore tubules push against one another
kinetochore tubules are depolymerized in order to shorten
functions of APC/C
frees separase from securin
degrades cyclins
events of telophase (3)
nucleoli reform
nuclear envelopes reform
remaining microtubules are depolymerized
events of cytokinesis (animals and plants)
Cleavage furrow is “pinched” by contractile ring of actin and myosin filaments
In plant cells, a cell plate forms - small cell wall fragments by vesicles
function of separase
cleaves cohesins, liberating sister chromatids from one another
function of securin
holds separase when not in use
constituents of contractile ring
actin and myosin
function of mitotic spindle
controls movement of chromosomes
spindle polymerizes from…
components of cytoskeleton
tubulin proteins
radial array of very short microtubules - contact plasma membrane, pointing away from equator
aster
kinetochores
protein complexes associated with centromeres
point of attachment for microtubules
ensures cell safely completes cycle
checkpoints
importance of G1 checkpoint
“restriction or start” point, major decision in the cell’s life
determines if cell will go on to S phase
if it goes on and fails, it will initiate apoptosis
importance of G2 checkpoint
ensures there is enough mitotic cyclin for mitosis to be completed
importance of mitotic checkpoint
when is it completed?
ensures equal separation of chromosomes
occurs after attachment of all kinetochore microtubules with equal tension on metaphase plate
is cyclin or CDK retained and reused?
which one has a variable concentration?
which one is degraded
CDKs retained
cyclins variable concentration
cyclins degraded
Cyclin D + Cdk4 + Cdk6
regulate movement from G1 to S phase
regulate S phase and G2 phase
Cyclin E + cyclin A + Cdk2
Cyclin B + cyclin A + Cdk1
mitotic complexes
triggers cell’s passage past G2 checkpoint into M phase
maturation-promoting factor
MPF’s negative feedback system
switches itself off by triggering the degradation of its cyclin component at the APC/C
molecular function of CDK complexes
phosphorylate other proteins in the cell, initiating kinase cascades which mediate the events of the cell cycle
released by other cells and stimulate division
growth factors
made by platelets, facilitating division of fibroblasts
platelet-derived growth factor
define density-dependent inhibition
division is inhibited when optimum cell density is reached in the immediate vicinity
define anchorage dependence
to divide, cells must be attached to substratum
3 steps of binary fission
increases in size, doubles its DNA, and splits
in binary fission, the DNA replicates at the…
point of origin
ensures DNA separates correctly during binary fission
tethering of DNA to each side of the cell by proteins
mitotic differences in diatoms & yeasts
nuclear envelope does not break down
mitotic differences in dinoflagellates
partial breakdown of the nuclear envelope to allow microtubules through
transformation
cell becomes able to divide indefinitely
