18.1 The Eukaryotic Cell Cycle Flashcards
4 main steps in the division cycle
- cell growth - maintains size of daughter cells
- DNA replication
- distribution of the duplicated chromosomes to daughter cells
- cell division
in the cell cycle, () is the most dramatic phase, yet most of the time the cell remains in interphase where the cell steadily grows (may reach up to double in size)
cell division (mitosis)
timing of DNA synthesis divides cell cycle into 4 main phases
- M phase
- G1 (gap 1)
- S phase (synthesis)
- G2 (gap 2)
cell cycle phase with mitosis (nuclear division); usually ends with cytokinesis
M phase
cell cycle phase that is the interval between mitosis and DNA replication; the cell is metabolically active and growing and there is no DNA replication
G1
cell cycle phase with DNA replication
S phase
cell cycle phase with synthesis of proteins in preparation for mitosis
G2
some cells remain in a prolonged resting state called () and only divide in response to the appropriate extracellular signals (e.g. skin fibroblasts in response to wounds)
G0
cells in G0 may reenter the cell cycle in response to ()
appropriate extracellular signals
DNA content at different stages of the cell cycle can be measured through (1) detected by a (2) or (3)
- fluorescence intensity
- flow cytometer
- fluorescence-activated cell sorter
DNA content in animal cells in G1
diploid
cells in S phase have DNA content ranging from (..)
2n to 4n
in G2, DNA content remains at (1) and decreases to () after cytokinesis
- 4n
- 2n
() is the most fundamental characteristic of cells → must be carefully regulated and coordinated
self-reproduction by cell division
extracellular signals that regulate animal cell cycle proliferation
growth factors
major cell cycle regulatory point; controls progression from G1 to S
START
START was first identified using studies involving ()
budding yeasts (Saccharomyces cerevisiae)
if requirements aren’t met, cells cannot progress past START and thus enter ()
G0 (cell cycle progress is arrested)
give examples of factors that regulate passage through START
- internal and external signals (availability of nutrients, cell size)
- presence of mating factors
regulatory point in G1 of animal cells; analogous to START in yeast cells
restriction point
passage through G1 restriction point is primarily regulated by (), which signal the cell’s permittance to proceed to synthesis and the rest of the cell cycle
extracellular growth factors
skin fibroblasts remain in G0 in adulthood until stimulated by () to proliferate and repair wound damange
platelet-derived growth factor (PDGF)
in fission yeast (Schizosaccharomyces pombe) cell cycle is controlled by transition from ()
G2 to M
the () of a fission yeast cell indicates its position in the cell cycle
length
vertebrate oocyte proliferation is signaled by ()
hormonal stimulation
without hormonal stimulation, vertebrate oocytes remain arrested in ()
G2
regulate the cell cycle by coordinating the different cell cycle phases
cell cycle checkpoints
cell cycle checkpoints prevent entry into the next phase of the cell cycle until ()
the events of the preceding phase have been completed
ensure that damaged DNA is not replicated (in G1 → S) and passed on to daughter cells (G2 → M)
DNA damage checkpoints
DNA damage checkpoints coordinate cell cycle progression with the ()
completion of DNA replication or repair (e.g. checkpoints in G1, G2)
() continuously monitors DNA integrity as well as acts as a quality control monitor to promote DNA repair
S phase checkpoint
stops mitosis at metaphase if chromosomes are not properly aligned on the spindle
spindle assembly checkpoint
spindle assembly checkpoint ensures that a () is distributed accurately to daughter cells
complete set of chromosomes
