Cell division Flashcards
What are the phases of cell cycle and outline processes
interphase- period of normal functioning, growth and DNA replication in prep for mitotic phase
Mitotic phase- (nucleus and cytoplasm divide), mitosis and cytokinesis=period of cell division
List 3 stages of interphase and outline what happens at each
G1= protein synthesis, organelles replicate, cell increases in size
S= synthesis, DNA is replicated in nucleus
G2=cell increases in size, energy stores increase, duplicated DNA checked for errors
List 2 stages of mitotic phase and outline what happens in both
Mitosis= nucleus divides
Cytokinesis= cytoplasm divides and 2 cells are produced
Describe significance of G0
phase when cell leaves cell cycle temporarily or permanently
- differentiation: cells no longer divide, they carry out their function indefinitely and don’t enter cycle again
- damaged DNA: damaged cells can no longer divide, preventing cancer
- regulates number of cells in tissue
Outline checkpoints role to control cell cycle
ensures a cell only divides once reached correct size
DNA replication is error-free
chromosomes are in correct positions during mitosis
3 examples of checkpoints
G1
G2
M (spindle assembly checkpoint)
when does G1 checkpoint occur
at end of G1 phase before entry to S phase
where does G2 checkpoint occur
end of G2 phase before entry to M phase
where does M checkpoint occur
during metaphase of mitosis
what does G1 checkpoint check
cell size, nutrients, growth factors, DNA damage
what does G2 checkpoint check
cell size, DNA replication, DNA damage
what does M checkpoint check
if all chromatids are correctly attached to spindle fibres
what happens if G1 checkpoint criteria are satisfied
Cell enters S phase and DNA replication begins
what happens if G2 checkpoint criteria are satisfied
molecular processes that signal beginning of mitosis are initiated
what happens if M checkpoint criteria are satisfied
cell continues with mitosis
what happens if G1 checkpoint criteria are not satisfied
cell enters G0
what happens if G2 checkpoint criteria are not satisfied
cell pauses G2 to try and repair, if irreparable then cell undergoes apoptosis
what happens if M checkpoint criteria are not satisfied
mitosis paused, repair attempted
define mitosis
nuclear division stage in mitotic phase of the cell cycle
define chromatids
one of two halves of a replicated chromosome
define sister chromatids
identical copies formed by DNA replication of a chromosome with both copies joined together by a common centromere
define sister chromatids
identical copies formed by DNA replication of a chromosome with both copies joined together by a common centromere
define centromere
region which holds 2 chromatids together
define spindle fibres
structures made of microtubules that organise chromosomes and pull them part to opposite poles during mitosis
define homologous pairs
matching pair of chromosomes, one inherited from each parent
describe how DNA is packaged in a chromosome
tightly packed DNA
found only during cell division
DNA not being used for macromolecule synthesis
describe how DNA is packaged in a chromatid
unwound DNA
found throughout interphase
DNA is being used for macromolecule synthesis
describe formation of chromosomes
- DNA is wrapped around histone proteins (compact)= chromatin
- during interphase, chromatin is decondensed
-during mitosis, chromatin is condensed=chromosomes