cell division Flashcards
what is the phase of the cell growth cycle in which the cell spends most of its time in?
interphase
Once the cell has grown enough, it begins to replicate its DNA in the _ phase
S
how does the cell prepare itself for division through?
mitosis
how does the cell split itself into daughter cells through?
cytokinesis
what is the cycle of growth and division called?
cell cycle
what are the 4 phases of the cell cycle?
G1
S
G2
M
what phases encompass interphase?
G1
S
G2
what phase occurs right after mitosis?
G1
what is the purpose of the G1 phase?
acts as a gap for the cell before needing to replicate its DNA and prepare again for cell division
what is the S phase know for?
synthesis of DNA
what happens during the S phase?
cell doubles its DNA in preparation for division
what is the gap between the S and M phase?
G2 phase
what is the M phase?
mitosis
what is the G0 phase?
cell becomes senescent, cell doesn’t grow or synthesize more DNA and remains “asleep” until it rejoins the cycle
what is the restriction point?
cell cycle checkpoint that occurs in G1 of the cell cycle in animal cells
The “commitment” step of this restriction point involves the formation of ___________________ that allow the cell to move on to the next phase.
cyclin/CDK complexes
what cyclin/CDK complexes form in the G1 phase?
S-phase cyclin complexes
what cyclin/CDK complexes form in the G2 phase?
M-phase cyclin/CDK complexes.
which checkpoint prevents the cell from going into mitosis before DNA synthesis has been completed?
unreplicated DNA checkpoint
what checkpoint makes sure that the newly replicated DNA has maintained its integrity?
G2 DNA-damage checkpoint
in which phase is there a spindle assembly and chromosome segregation checkpoint?
M phase
what is the purpose of cyclin/CDK complexes?
proteins come together and form a functional enzyme that can then modify downstream target proteins, helping the cell progress through the cell cycle.
list the cyclins and CDKs associated with the G1 phase
cyclin D
CDK 4
CDK 6
list the cyclins and CDKs associated with the S phase
cyclin E
cyclin A
CDK 2
list the cyclins and CDKs associated with the G2 phase
cyclin A
CDK 1
list the cyclins and CDKs associated with the M phase
cyclin B
CDK 1
what is the purpose of tumor suppressors?
proteins that prevent the unregulated growth/division of cells by promoting apoptosis, inhibiting cell growth, or maintaining DNA
what are the two categories the tumor suppressor proteins can be divided into
caretakers and gatekeepers
which category of tumor suppressor proteins make sure that the genome remains stable through DNA repair?
caretakers
which category of tumor suppressor proteins regulate cell growth by inhibiting cell cycle progression?
gatekeepers
what tumor suppressor protein prevents the progression of the cell from G1 to S?
Retinoblastoma protein (Rb)
when is Rb active?
resting cells remaining in G1
what state is Rb in when it’s active?
hypophosphorylated (no phosphate attached)
When the cell is ready to progress to S from G1, we will have an increased presence of what cyclins and CDK?
cyclin D
CDK 4
CDK6
what enzyme adds more phosphate groups to Rb?
kinases
what state is the Rb in when it is inactive?
hyperphosphorylated (many phosphates added)
When Rb is inactive, it will cause it to dissociate from what protein?
E2F
what does E2F do?
activate gene expression of cyclins E and A for progression into the S phase
what tumor suppressor protein is a caretaker protein and called “the guardian of the genome”?
p53
what is the purpose of p53?
ensures that DNA’s integrity is maintained
If p53 notices any DNA damage, it arrests the cell in the ____ checkpoint and activates DNA repair mechanisms.
G1/S
how does p53 arrest the cell?
CDK inhibitor p21
If p53 recognizes that this DNA damage cannot be repaired, it activates apoptosis by inducing the transcription of the protein ___, which induces apoptosis.
BAX
what is retinoblastoma?
childhood cancer that occurs due to a mutation in the Rb gene which is located on chromosome 13
what can happen when tumor suppressor genes lose their function due to a mutation?
cause cancer
what must happen for cancer to develop by having a mutated tumor suppressor gene?
both genes must have a loss of function
why is retinoblastoma considered a familial cancer?
most children inherit one defective Rb allele from a parent who is a carrier
what is the two hit hypothesis?
- once the second Rb gene is mutated, they will develop this cancer
- in order to develop cancers due to loss of function of a tumor suppressor gene, you must have two hits on the tumor suppressor gene (losing function in both genes)
what are symptoms of retinoblastoma?
leukocoria (abnormal white retina appearance)
loss of vision
glaucoma
cross-eyed vision
what is mitosis
process of cell division to create an identical daughter cell
list the different phases of mitosis in order
prophase
prometaphase
metaphase
anaphase
telophase
cytokinesis
which mitosis phase involves condensation of the replicated DNA into chromosomes?
prophase
during prophase, because the DNA has duplicated in the S phase, each chromosome will consist of two sister chromatids that are joined together by a _______.
centromere
during prophase, microtubules in the cytoskeleton aggregate around ________, which are the microtubule-organizing centers, which will be used as part of the ___________
centrosomes
mitotic spindle
what is the start of prometaphase characterized by?
breakdown of the nuclear envelope where the spindle can then enter the nuclear area
during prometaphase, what are the structure that begin to develop on the centromeres of the chromosomes?
kinetochores
during prometaphase, what do the kinetochores attach to?
kinetochore microtubules
what is metaphase characterized by?
where the chromosomes are lined up in the middle of the cell
how are the alignment of chromosomes done during metaphase?
kinetochore microtubules and motor proteins
what happens during anaphase?
chromosomes separate into chromatids that go to opposite poles of the cell
which phase is faster, anaphase or metaphase?
anaphase
what happens during telophase?
the separated sister chromatids arrive at the opposite poles and the kinetochore microtubules begin to disappear
what happens during cytokinesis?
cells separate to make two new daughter cells
what phase does cleavage occur?
cytokinesis
how is a cleavage furrow created?
contractile ring of actin filaments, and it gradually becomes deeper and deeper until both sides reach the remaining mitotic spindle that is still present between the two new nuclei