Term
| Describe the 4 requirements for life |
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Definition
1. Boundary- what is you and not you; where to stop
2. Metabolism- harness energy
3. Hereditary material- DNA
4. CONTROLLED Reproduction |
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Term
| Describe the phases of the cell cycle |
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Definition
M: mitosis- nuclear division ending with cell division
G1: prepare for DNA synthesis (2n)
S: DNA synthesis (2nG2: replicate organelles, make sure DNA is fine (4n) |
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Term
| Describe the regulatory point S. cerevisiae |
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Definition
START
-at the end of G1 before S
1. Divide 2. Die
Looks for:
a. nutrients b. cell size c. mating factors |
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Term
| Describe the regulatory point in animal cells |
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Definition
Not START but called restriction point in late G1
Looks for: Growth factors
*without GFs cell with go to resting state called Go
ex. skin fibroblasts will remain in Go until stimulated with PDGF released from platelets |
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Term
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Definition
1. S. pombe relies on nutrients and size in G2
2. Human oocytes arrest in G2
-stimulated by hormones to M phase |
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Term
Describe the cell cycle checkpoint
1. DNA damage
2. Spindle Assembly |
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Definition
1. cell cycle is arrested is DNA is damage or unreplicated
a. End of G1 b. Mid of S c. End of G2
2. ensures that chromosomes are evenly distributed
-metaphase of M |
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Term
| Describe how the cell regulates one round of DNA replication |
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Definition
Cell must ensure that DNA is replicated only once
1. MCM helicase proteins bind OriC site with ORC that are required for initiation of DNA replication
2. MCM opens up DNA for DNA poly
3. At initiation, MCM are displaced
-replication can't happen until after mitosis |
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Term
Describe the following experiments that identified the molecules responsible for cell cycle regulation:
1. Frog oocytes
2. Yeast temperature mutants
3. Sea urchin embryos |
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Definition
1. eggs arrest in G2 until stimulated by progesterone
-forms MPF
-appears in somatic cells as well
-acts as general regulator for entry into M
2. temperature sensitive cdc genes are required for START
-encode protein kinases
-cdk1
3. proteins accumulated in interphase and degraded after M
-called cyclins
-protein synthesis is slowed so cyclins decrease |
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Term
| Describe the relationship between MPF, cyclins, and Cdk1 |
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Definition
MPF= Cdk1/cyclin B
Cyclin B- regulatory subunit required for catalytic activity of Cdk1
-cyclins must be at high levels to activate Cdk1 |
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Term
| Describe regulation of MPF |
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Definition
1. Cdk1 phospho at Thr161 (activates) and Tyr14 and Thr15 to deactivate
2. dephospho of Tyr14 and Thr15 activate Cdk1/cyclin and it initiates M phase
3. cyclin B is degraded by ubiquitin |
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Term
| Describe the 4 mechanisms of Cdk regulation |
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Definition
1. Cdk/cyclin complex
-controlled by cyclin synthesis and degradation
2. activation of cdk/cyclin at Thr161
-catalyzed by CAK (Cdk7/cyclin H)
3. inhibited by phospho at Tyr14 and Thr15
-catalyzed by Wee1
-dephospho by Cdc25 to activate
4. Cdk inhibitor proteins bind and inhibit
-Ink4 (G1) and Cip/Kip (G1 and S) |
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Term
| Describe the progression into S phase: Cdk2/cyclin E |
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Definition
1. in G1 or Go, Cdk2/cyclin E is inhibited by p27
2. cyclin E synthesis is stimulated by E2F
-E2F is activated when Rb is phospho and deactivated
-p27 is inhibited by growth factor signaling (PI3/Atk)
3. Cdk2/cyclin E activates MCM
-DNA replication |
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Term
| Describe cell cycle arrest due to DNA damage |
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Definition
ATM- ds breaks
ATR- ss breaks
1. activate checkpoint kinase
ATM phosphos Chk2
ATR phosphos Chk1
2. Chk inactivate Cdc25
-responsible for removal of inhibitory phosphates on Cdk1 and Cdk2 at Tyr14 and Thr15
Cdk2- cell cycle stops at G1 and S
Cdk1- cell cycle stops at G2 |
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Term
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Definition
1. ATM responds to ds break
-activates Chk2
2. Chk2 and ATM phospho p53
-if not activated, rapidly degraded
3. p53 is TF that turns on p21
-Cdk inhibitor
4. p21 inhibits Cdk2/cyclin E
-stops at G1
*mutant p53 can't stop cell division if DNA is mutated |
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Term
Describe the stages of Mitosis
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase |
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Definition
1. appearance of sister chromatids
-attach at centromere
-centrosomes move to ends of cell
-nucleus breaks down
2. chromosomes align at central plate
-microtubules attach to kinetochores
3. sister chromatids break to opposite ends
4. nucleus reform and chromosomes decondense
-cytokinesis |
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Term
Describe the activation by MPF
1. Chromatin condensation |
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Definition
*condensation driven by condensin
1. cohesins bind DNA is S phase to keep sister chromatids together
2. Cdk1/cyclin B phosphorylate condensins to activate
3. chromatids condense and cohesins only bind at centromere |
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Term
Describe the activation by MPF
2. Breakdown of nuclear envelope |
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Definition
1. phospho of lamins by Cdk1/Cyclin B depolymerizes them
-breaks down lamin structure and nuclear membrane
2. also phosphos nuclear pore complex |
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Term
Describe the activation by MPF
3. Golgi fragmentation |
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Definition
1. Cdk1/cyclin B phosphos Golgi
-COPI proteins
-inhibits docking and fusion |
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Term
Describe the activation by MPF
4. Centrosome maturation |
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Definition
1. Cdk1/cyclin B phosphos to separate centrosomes
2. increased microtubule turnover activated by Cdk1
-also Aurora and Pololike kinases |
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Term
| Describe the spindle assembly checkpoint |
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Definition
1. APC/C and Cdc20 are blocked from activation by Mad/Bub proteins attached to kinetochores
2. Once all chromosomes align, Mad/Bub leave
-Cdc20 is free and activates APC/C
3. APC/C ubiquinates:
a. cyclin B- Cdk1 is inactivated
b. Securin- bound to separase
-separase is free degrade coehsin and separate chromatids |
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Term
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Definition
1. triggered by inactivation of Cdk1
2. pinched by contractile ring of actin and myosin II
3. lines at metaphase plate and pull membrane inward |
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Term
Describe the Meiosis at the end of each stage
1. Meiosis I
2. Meiosis II |
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Definition
1. Homologous chromosomes (mom and dad) separate
-sister chromatids left in cell
2. sister chromatids (exact copies) separate
-one member of homologous chromosomes left (n)
*meiosis similar to mitosis* |
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Term
Describe recombination of homologous chromosomes
1. Leptotene
2. Zygotene
3. Pachytene
4. Diplotene
5. Diakinesis |
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Definition
*occurs during prophase of meiosis I
1. ds breaks by Spo11
2. synapsis (close association)
3. crossing over occurs
-linked at sites called chiasmata
4. chromosomes separate except at chiasmata
5. transition to metaphase |
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Term
| Describe Oocyte regulation |
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Definition
1. can remain in arrest during diplotene for 50 years
-chromosomes decondense and are transcribed
2. hormonal stimulate proceeds cell through meiosis I
-activates Cdk1/cyclin B
3. cyclin B falls after metaphase I
-rises at the end of meioI and remains high during MeioII
4. metaphase II arrest is caused by CSF
-cytostatic factor
-serine/threonine kinase (Mos)
-keeps Cdk1/cyclin B levels high so it can't progress past metaphase |
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Term
| Describe the process that occurs when a sperm enters the egg |
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Definition
1. sperm have specific receptors for egg sugar modifications
2. sperm binds and increases Ca levels
-PIP2 hydrolysis
a. induces surface alterations so no more sperm can enter
b. signals completion of meiosis
-activate APC/C to degraded cyclin B
3. pronuceli replicate DNA together
-chromosomes of both parents align on spindle |
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