Exam 2 - Cell Cycle Flashcards
What happens in S phase?
Chromosome duplication/DNA replication
What happens in M phase?
Mitosis and cytokinesis
What are the two parts of a human mitotic chromosome called?
Sister chromatids
When is the only time that a chromosome will condense?
When a cell is undergoing mitosis
What is the end result of the M phase?
Two diploid (daughter) cells
What are the 6 stages of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
What happens during prophase?
Replicated chromosomes condense, mitotic spindles assemble
What happens during prometaphase?
Breakdown of nuclear envelope; chromosomes attach to spindle microtubules via kinetochores
What happens during metaphase?
Chromosomes are aligned at the equator of the spindle; kinetochores attach sister chromatids to opposite poles of the spindle
What happens during anaphase?
Sister chromatids synchronously separate to form two daughter chromosomes; each chromatid is pulled toward the spindle pole it faces
What happens during telophase?
Daughter chromosomes arrive at poles of the spindle and decondense; new nuclear envelope assembles
What happens during cytokinesis?
Cytoplasm divided in two by actin and myosin filaments; two daughter cells form, each with their own nucleus
What are the 3 stages of interphase?
- G1 (gap phase)
- S
- G2 (gap phase)
At what stage does the cell cycle arrest?
G0
What type of Cdk does yeast have?
Cdk1
How do the Cdks of yeast vary from those of vertebrates?
Yeast has one, vertebrates have several
What happens to cyclin at each stage of the cell cycle?
Levels fluctuate
How does Cdk activity relate to cyclin binding?
It rises and falls in response to cyclin binding
How are cyclins made and degraded?
Cyclically in dividing cells
When is the only time that Cdk is active?
When their cyclin is around
What are the 3 ways to regulate activity of the Cdk-cyclin complex?
- Phosphorylation/dephosphorylation
- Cdk inhibitor protein-binding to cyclin-Cdk
- Cdk inhibitor protein degradation
What does CAK do?
Fully activates Cdk
What does Cdc25 do?
Counteracts Wee1
What does Wee1 do?
Inhibits Cdk through phosphorylation
What do CKIs do?
Inhibit Cdks
What are the 3 checkpoints in the cell cycle?
- G1/S
- G2/M
- M/G1
What questions are asked at the G2 checkpoint?
Is all the DNA replicated?
Is the environment favorable?
What question is asked at the metaphase checkpoint?
Are all chromosomes attached to the spindle?
What question is asked at the G1 checkpoint?
Is the environment favorable?
What 3 proteins are important for cell cycle control?
- Retinoblastoma
- Ras
- p53
What is retinoblastoma involved with?
Cell cycle arrest
What is Ras involved with?
Stimulates cell division; action at G2/M checkpoint
What is p53 involved with?
Stops cell division momentarily; action at G2/M checkpoint
What is retinoblastoma?
Tumor suppressor
What happens when Rb is inactive or mutant?
Cell enters S phase –> aggressive tumor in the retina
- Treatment = bilateral enucleation
What effect does activated Ras have on Rb?
Indirectly inactivates Rb
What protein binds p53 and what does it do?
mdm2; inhibits p53 activity
What two proteins are necessary for sister chromatid cohesion?
- Cohesin
2. Condensin
What does protease separase do?
Cleaves cohesin allowing sister chromatid separation
What is the chromosome phenotype after inactivation of cohesin?
Precocious sister chromatid separation
What is the chromosome phenotype after inactivation of condensin?
Unresolved sister chromatids
What is the chromosome phenotype after inactivation of separase?
Diplochromosomes (re-replicated, non-disjoined chromatids)
What are 4 anti-cancer therapy strategies aimed at all dividing cells?
- Inhibition of microtubule polymerization
- Severe DNA damage
- Interfere with cell metabolism
- Inhibit DNA synthesis
What is psoriasis?
Hyperplastic skin disease where inflammation causes excessive skin proliferation
What is avian pox?
Hyperplastic skin disease that induces epidermal proliferation and hyperkeratosis
