Cell Cycle 1 Flashcards
What happens in cell reproduction?
duplication of contents of cell (chromosomes and organelles)
divide cell into two (cytokinesis)
What are the three major functional aspects of the cell cycle?
- cell growth and chromosome replication
- chromosome segregation
- cell division
What is the goal of the cell cycle?
produce two genetically identical daughter cells
How often do mistakes occur in the cell cycle?
rate of 1 x 10^-9 per replication
6 mistakes occur in one cell division
Cancer is a disease of excess cell _______
proliferation
Chromosome duplication is in the ___ phase of cell cycle
S
Chromosome segregation and cell division occur during ____ phase of cell cycle
M
What is cytokinesis?
cell division
What occurs during prophase?
chromosomes condense into rigid rods called sister chromatids (become attached to mitotic spindle: a bipolar array of microtubules)
What occurs during metaphase?
sister chromatids line up at equator of cell attached to opposite poles of spindle
What occurs during anaphase?
sister chromatids become daughter chromosomes and are pulled to opposite poles of spindle
What occurs during telophase?
spindle disassembles, chromosomes packaged into separate nuclei, cytokinesis occurs
What are the GAP phases?
phases which allow for more time to grow
When does G1 phase occur?
between M and S
When does G2 phase occur?
between S and M
Describe checkpoint 1
Start, cell commits cycle entry and chromosome duplication
Describe checkpont 2
G2/M- chromosome alignment on spindle in metaphase
Describe checkpoint 3
metaphase to anaphase transition- trigger sister chromatid separation and cytokinesis
Describe fission yeast
grows by elongation at ends; division occurs when septum or cell plate form midway along rod shaped cell
Describe budding yeast
oval yeast that divides by forming a bud; the bud first appears at G1 and grows until mitosis phase
What are immortalized cell lines?
cell lines grow forever
What do cyclin dependent kinases (Cdks) do?
phosphorylate proteins downstream to activate them and regulate cell cycle events
What are the proteins that regulate Cdks?
cyclins
Cdks must be _____ to cyclin to have protein kinase activity
bound
Are Cdk levels constant?
yes, only cyclin levels vary
What do G1/S cyclins do?
start cell cycle by activating Cdks in late G1
What do S cyclins do?
duplicate DNA
What do M cyclins do?
mitosis
______ of Cdks rise and fall during cell cycle
________ of cyclins rise and rall
activities; levels
When binding cyclin to Cdk, what happens to the t-loop?
it moves out of the active site and phosphorylation occurs, allowing for fully activated enzyme
How does Wee1 kinase inhibit Cdk activity?
by phosphorylating the roof site
How does Cdc25 increase Cdk activity?
It is a phosphatase that dephosphorylates roof site to increase activity
What are CKI proteins?
Cdk inhibitory proteins that causes cyclin-Cdk complex to be inhibited
What is INK4A?
CKI involved in G1 phase of cell cycle
_____ occurs in INK4A gene in hereditary melanoma. Which results in what?
mutation
cannot control cell cycle and cells grow uncontrollably and you get cancer
What is p53?
a major tumor suppressor
What does p53 do to p21?
up regulates it
What is p21?
CKI to stop cell division
What happens when there is a fail in function for p53?
lower p21 expression and without this CKI cells divide uncontrollably– cancer
Proteolysis of CKI’s can turn on ______
S-Cdk’s
What controls mitosis?
M-Cdk
What is the inactive form of m-cdk?
cyclin-M cdk complex
What holds M-cdk in inactive state?
Wee1
activation of primed M-cdk is by _____
Cdc25 protein phosphatase
What two proteins affect the APC/C system?
cohesin and securin
What does cohesin do?
glue sister chromatids together by their length
What does securin do?
protects cohesion protein linkages that hold sister chromatid pairs together in early mitosis
Securin ______ cohesins
protects
How does securin protect cohesin?
inhibiting a protein called separate, an enzyme that cleaves cohesin
