2.6.1 the cell cycle & it's regulation Flashcards
cytokinesis
cytoplasmic division following nuclear division, resulting in 2 new daughter cells
interphase
phase of cell cycle where cell isn’t dividing; it is subdivided into growth & synthesis phases
mitosis
type of nuclear division which produces daughter cells genetically identical to each other & parent cell
how is the cell cycle regulated
2 main cell-cycle checkpoints:
- G1/S checkpoint (restriction point)
- G2/M checkpoint
another name for G1/S checkpoints
restriction point
purpose of cell-cycle checkpoints
- prevent uncontrolled division which would lead to tumours (cancer)
- detect & repair damage to DNA (eg. caused by UV light)
what does the molecular events controlling the cell cycle happening in a specific sequence ensure
- cell cycle can’t be reversed
- DNA only duplicated once during each cell cycle
list the order of phases within the cell cycle
- M phase
- G0 (gap 0) phase
- G1 (gap 1) phase - growth phase
- S (synthesis) phase of interphase
- G2 (gap 2) phase of interphase
describe the M phase
- checkpoint chemical triggers condensation of chromatin
- halfway through cycle, metaphase checkpoint ensures cell ready to complete mitosis
events within cell during M phase
- cell growth stops
- nuclear division (mitosis) = prophase, metaphase, anaphase & telophase
- cytokinesis (cytoplasmic division)
describe G0 (gap 0) phase
- resting phase triggered by early G1 at restriction point, by checkpoint chemical
- some cells (eg. epithelial) don’t have this phase
events within cell during G0 (gap 0) phase
- cells may undergo apoptosis, differentiation or senescence
- some types of cells (eg. neurones) remain in phase for long time/indefinitely
apoptosis
programmed cell death
describe G1 (gap 1) phase
- at G1 checkpoint, control mechanism ensures cell ready to enter S phase & begin DNA synthesis
events within cell during G1 (gap 1) phase
- cells grow & size increases
- transcription of genes to make RNA
- organelles duplicate
- biosynthesis eg. protein synthesis, make enzymes needed for DNA synthesis in S phase
- p53 (tumour suppressor) gene helps control phase
describe S (synthesis) phase of interphase
- as chromosomes unwound/DNA is diffuse, every molecule of DNA is replicated
- specific sequence to replication of genes:
–> housekeeping genes replicated first
–> genes which are normally inactive in specific cells replicated last
events in cell during S (synthesis) phase of interphase
- cell committed to completing cell cycle
- DNA replicates
- when all chromosomes duplicated, each consists of pair of identical sister chromatids
- phase is rapid & because exposed DNA base pairs more susceptible to mutagenic agents, this reduces chances of spontaneous mutations occurring
describe G2 (gap 2) phase of interphase
- special chemicals ensure cell ready for mitosis by stimulating proteins that will be involved in making chromosomes condense & in formation of spindle
events within cell during G2 (gap 2) phase of interphase
cells grow
