Final Exam - Cell Cycle Flashcards
What are the three phases of interphase?
G1 phase, S phase, G2 phase
What occurs during the G1 phase?
gap phase; chromosomes in the nucleus
What occurs during the S phase?
DNA synthesis and chromosome duplication
What occurs during the G2 phase?
gap phase; cell with duplicated chromosomes
What are is the M phase?
mitosis
What are the phases of mitosis?
prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis
What happens during prophase?
- the replicated chromosomes, each consisting of two closely associated sister chromatids, condense
- outside the nucleus the mitotic spindle assembles between the two centrosomes
What happens during prometaphase?
starts with the breakdown of the nuclear envelope
What happens during metaphase?
- the chromosomes are aligned at the equator of the spindle midway between the spindle poles
- the kinetochore microtubules attach sister chromatids
What happens during anaphase?
the sister chromatids synchronously separate to form two daughter chromosomes and each is pulled slowly toward the spindle pole it faces
What happens during telophase?
- the two sets of daughter chromosomes arrive at the poles of the spindle and decondense
- a new nuclear envelope reassembles around each set, completing the formation of two nuclei, marking the end of mitosis
What happens during cytokinesis?
the cytoplasm is divided in two by a contractile ring of actin and myosin filaments which pinches the cell in two to create two daughter cells
What is the G0 phase?
cell cycle arrest
What is the function of cyclins?
they are made and degraded cyclically in dividing cells
What is the purpose of the G1/S-CDK complex?
initiates cell cycle entry
What is the purpose of the S-CDK complex?
initiates DNA replication
What is the purpose of the M-CDK complex?
initiates mitotic entry
When are cyclin-dependent kinases activated?
only when their cyclin is around
What is the function of Wee1?
inhibits Cdk through phosphorylation
What is the function of cdc25?
counteracts the function of Wee1
What is the function of CK1?
cdk inhibitor proteins bind to cdk-cyclin complex and physically block its ability to interact with other proteins
What is a Rb?
retinoblastoma is a tumor supressor which arrests cells at the G1/S checkpoint and stop transcription by inhibiting E2F transcription factor
In normal function, what is rb activated by?
G1-Cdk via Ras+MAP kinase pathway
What is p53?
a tumor supressor
What does p53 do?
senses DNA damage and arrests cell division at G2/M checkpoint if necessary
What does the checkpoint kinase detect?
detects damage and signal pH of p53. Activates p53 which activates the transcription of p21=CDK inhibitor - cell cycle stops for repair
What does Ras do?
stimulates cell division by indirectly inactivating Rb, liberating E2F and allowing the cell to pass through the G1/S checkpoint
What are the cell cycle checkpoints?
- G1/S
- G2/M
- M/G1
Where is the G1/S checkpoint located?
right before the S phase
What ‘question’ does the G1/S checkpoint ask?
is the environment favorable
Where is the G2/M checkpoint located?
right before M
What ‘questions’ does the G2/M checkpoint ask?
is the DNA replicated
is the environment favorable
Where is the M/G1 checkpoint located?
in the completion of mitosis/metaphase checkpoint
What ‘question’ does the M/G1 checkpoint ask?
are all the chromosomes attached to the spindle
What can happen if Rb is inactive of mutant?
cells enter S phase and form an aggressive tumor
What is the treatment for an inactive or mutant retinoblastoma?
enucleation prior to metastasis
What happens in psoriasis?
hyperplastic skin disease exhibiting as inflammation and excessive skin proliferation
What happens in avian pox?
hyperplastic skin disease exhibiting as epidermal proliferation and hyperkeratosis
