Mitogens are involved in cell signaling pathways which promote cell division by
ID: 274134 • Letter: M
Question
Mitogens are involved in cell signaling pathways which promote cell division by the production of cyclin. Using the figure 18-14 from your book (which is on the right), answer whether the expression of genes required for cell proliferation will be increased or decreased under the following scenarios.
Mutation in the Rb protein which prevents it from being phosphorylated by G1-Cdk complex.
Alterations in the signal transduction from the activated mitogen receptor so that G1-Cdk complex is not activated.
Increased activation of the G1-Cdk complex.
In which phase of the cell cycle does the average cell spend its most time? _______________________________
Before a cell undergoes mitotic cell division:
what has to happen first, regarding its DNA?
If (what you wrote in 2a) didn’t happen, what problem would arise?
There are some cells which after they mature (fully differentiate into their specific cell type) never undergo division (such as heart muscle cells) again. These cells are in what phase? _________
How are phosphates involved in regulating the activity of a cyclin dependent kinase (Cdks)?
7. How does cytochrome c initiate apoptosis? What are the roles of Bax and Bak in this initiation? How does Bcl affect apoptosis?
8. For the list below, indicate which statements are true of the G1, G2, S, or M phase of the cell cycle. A statement may be true of any or all of the phases.
a. _______ the amount of nuclear DNA doubles
b. _______ the nuclear envelope breaks into fragments
c. _______ sister chromatids separate from one another
d. _______ cell that never divide again will be in this stage
e. _______ chromosomes are present in a condensed state
f. _______ mitotic cyclin is at its highest level
g. _______ a Cdk protein is present in the cell
h. _______ a cell cycle checkpoint has been identified in this phase
i. ________ nuclear envelope reforms
j. ________ cohesion proteins break down
k. ________ cell is active in doing its “job”
l. _________ cell is getting ready to make proteins needed for cell division
m. __________ S cyclin is at its lowest concentration
Explanation / Answer
8.
ANSWERS :
a. _______ the amount of nuclear DNA doubles = S phase
The cell's nuclear DNA contents are duplicated during S phase and may continue till G2 if heterochromatin.
b. _______ the nuclear envelope breaks into fragments = M phase
When cell is ready to divide, the nucleus break up so that chromosomes line up and be distributed between the two daughter cells during M phase.
c. _______ sister chromatids separate from one another = M phase
When chromosomes lined up along the central axis of the cell, then centromere break up and sister chromatids pulled to either pole of the cell durung M phase.
d. _______ cell that never divide again will be in this stage = G1 phase
For cell division cells undergo DNA replication during S phase. But, if the cell will not divide then it will remain in the G1 phase, before S phase
e. _______ chromosomes are present in a condensed state = G1, G2, S, or M phase of the cell cycle.
During interphase, chromatin is in condensed state and appears loosely distributed throughout the nucleus and hromatin condensation begins during prophase, chromosomes become visible.
f. _______ mitotic cyclin is at its highest level = M phase
M cyclin peaks dramatically at the transition from G_2 to M phase
g. _______ a Cdk protein is present in the cell = G1, G2, S, or M phase of the cell cycle.
Cyclin dependent protein phosphorylates proteins and present throughout the cell cycle and multiple Cdks are used at different points of the cell cycle.
h. _______ a cell cycle checkpoint has been identified in this phase = G1, G2, or M phase of the cell cycle.
Cell cycle checkpoints determine if the cell is ready to move to the next phase.
G1 checkpoint determine cell should divide or enter a resting period.
G2 checkpoint determine if the cell is ready to undergo mitosis.
M checkpoint makes sure that the chromosomes are properly aligned and segregated into 2 daughter cells.
i. ________ nuclear envelope reforms = G1 phase
Nuclear envelope reforms during anaphase and lasts into G1 phase of the cell cycle.
j. ________ cohesion proteins break down = anaphase
k. ________ cell is active in doing its “job” = G1, G2, S, or M phase of the cell cycle.
l. _________ cell is getting ready to make proteins needed for cell division = M phase