In cell cycle: a. M phase is both the most complex and the longest phase b. ther

Question

In cell cycle:

a. M phase is both the most complex and the longest phase

b. there is a G0 phase in equilibrium with the G1 phase

c. quiescent cells cannot be induced to reenter the cell cycle

d. microtubule spindles form during the S phase

e. the order of phases is G1, G2, S, and M

2. cyclin-dependent kinase (Cdks):

a. occur onlu int he M phase

b. are always inactivated by phosphorylation

c. typically phosphorylate proteins on tyrosine residues

d. in addition to binding cyclin, require other modifications for activity

e. that phosphorylate Rb (retinoblastoma sensitivity) protein inhibit the synthesis of S-phase proteins

3. elements of growth factor pathway regulation of the cell cycle include all of the following except:

a. dimerization or polymerization of receptor proteins in the plasma membrane

b. binding of ATP to a tyrosine kinase domain of growth factor receptor proteins

c. nonspecific bidning of SH2 or SH3 domains to any phosphorylated tyrosine

d. conformational changes of proteins as part of signal transmission

e. location of the growth factor receptor protins in the plasma membrane

4. one inducer of apoptosis is DNA damage acting via p53, a transcription factor, p53:

a. is activated by kinases located in chromatin

b. increases the transcription of several pro-apoptotic genes for Bcl-2proteins

c. concentration is normally because it is subject to ubiquitination

d. concentration may be increase by acetylation

e. all of the above are correct

8. Ras proteins of the signal pathway

a. is inactive in the GDP-Ras conformation

b. transmits a signal by initiating a kinase cascade

c. from a mutated gene in many cancers has inactiavted GTPase activity so inhibits the downstream signal to divide

d. is formed from an oncogene

e. becomes inactive as a signaling prtein by phosphorylation transcription factors.

9. apoptotic death of a cell may include all the follpwing except:

a. lysis of the cell membrane with inflammatino

b. activation of enzymes called caspases

c. phagocytosis

d. bidning of a ligand in the extracellular environment to a plas membrane receptor

Explanation / Answer

1). a. M phase is both the most complex and the longest phase ------> FALSE (Interphase is both the most complex and the longest phase, occurs for about 14 hours)

b. there is a G0 phase in equilibrium with the G1 phase ------> TRUE

Interphase is subdivided into three phases, namely the G1 (gap-one), S (synthesis), G2 (gap-two) phases. The cells in the G0 phase are in the quiescent state. They do not either divide or prepare to divide. It is observed during the extended G1 phase.

c. quiescent cells cannot be induced to reenter the cell cycle ---> FALSE (quiescent cells can reenter the cell cycle once they are repaired)

d. microtubule spindles form during the S phase ----> FALSE (microtubule spindles form during the prometaphase)

e. the order of phases is G1, G2, S, and M ---> FALSE (The order of phases is, G1, S, G2 and M)

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