L3 Cell Cycle, Meiosis and Mitosis Flashcards
what cells are found in the cell cycle?
eukaryotic somatic cells that have the capacity to divide
what is the cell cycle?
the time from birth of a new cell until it is capable of cell division to form 2 new daughter cells
what are the 2 stages of the cell cycle?
interphase - period between cell division
mitosis - period of actual cell division
which phase is most variable?
interphase
in what stage does the cell spend most time?
interphase - variable from one cell type to the next
what happens to the cell during interphase?
the cell grows - ready for mitosis at the end of interphase
what happens to the cell during mitosis?
the cell actually divides to form 2 new daughter cells
time spent in mitosis is 2-4 hours and is usually constant
what are labile cells?
multiply throughout life
cells of skin, GIT, epithelial cells
they have short interphases
what are stable cells?
quiescent (G0 phase)
can divide if stimulated by growth factors
liver cells
what are permanent cells?
lost the capacity to divide
permanently in G0 phase
neurons, cardiac muscles cells etc.
what is the most significant checkpoint?
G1 checkpoint - checks for cell size, nutrients, growth factors and DNA DAMAGE
what happens during G1 phase?
cell size increase
protein synthesis active
cell differentiation and performs functions
at the end, cell checks whether it is ready for division
what is the G0 phase?
(quiescent)
permanent and stable cells in here
stable cells can re-enter with GFs
what happens during S phase?
DNA synthesis/DNA replication enzymes of replication are active chromosome number x2 chromatid number x2 1 chromosome = 2 sister chromatids
what happens during the G2 phase?
chromatid number x2
cell size increases (help form new daughter cells)
genome is scanned for mistakes
DNA repair mech. active
what proteins are important at the G1–>S checkpoint?
p53 and Rb (tumor suppressor genes)
what are cyclins?
regulate the entry of cells into the various phases of the cell cycle
what are the functions of p53?
- cell cycle arrest
- DNA repair
- apoptosis - if DNA is damaged badly
what do growth factors do?
stimulate cell division
serve as signals that tell the cell to move though the cell cycle in order to divide
cells have a ___ lifespan
finite - some point no longer able to divide
what is cancer in terms of the cell cycle?
defect in the regulation of the cell cycle - rapidly dividing cells that are no longer controlled!
in non-stressed cells, what is the concentration of p53?
low - visa versa
what is a chromatid?
copy of a duplicated chromosome which is joined by a centromere
what happens during mitosis?
sister chromatids are divided and cytoplasmic division forms 2 daughter cells
