After synchronizing mammalian cells in culture with a double thymidine block (cell cycle duration of 24h), cells are released into fresh medium. After 6h, cells are split into 4 sets and each is treated with a) nothing, b) proteasome inhibitor, c) myosin II inhibitor, d) nocodazole.
From the options given below, choose the one that has the most likely outcome of the experiment.
EXPLANATION-
a) Nothing → cells continue dividing → synchronously dividing cells
b) Proteasome inhibitor → metaphase arrest
c) Myosin II inhibitor → cytokinesis blocked → binucleate cells
d) Nocodazole → spindle disrupted → prometaphase arrest
so, the correct option is (d)- a: synchronously dividing cells; b: metaphase arrested; c: binucleate cells; d: pro-metaphase arrested
Following statements were made about cell cycle regulation:
A.De novo synthesis and destruction of Cyclin B are essential for cell cycle progression in yeast.
B.De novo synthesis and destruction of Cyclin B and the related Cyclin dependent Kinase (CDK) are essential for cell cycle progression.
C. CDK activity is regulated by both activating and inhibitory phosphorylation.
D. Retinoblastoma (Rb) functions as an inhibitor of G2 to M transition.
E. Inactivation of Sic 1 is essential for transition into S phase.
Which one of the following represents the combination of the correct statements?
DNA replication occurs in S phase. The entry of cells into S phase is regulated by the tumor suppressor protein Rb. The statements below are made with reference to the role of Rb.
A. Rb binds to E2F in the cytosol and prevents E2F entry into the nucleus.
B. Rb is phosphorylated by cyclin A/cdk 4.
C. Phospho-Rb activates E2F.
D. E2F activates cyclin E production which promotes the G1/S transition.
Which one of the following options represents all correct statements?
Following statements were made about chromosome cohesion during mitosis and meiosis.
A. Though cohesin is important for pairwise alignment of the chromosomes on the mitotic spindle, it is not important for the generation of tension across the centromere.
B. Cohesin binds to the chromosome even before the onset of S-phase.
C. In fission yeast, centromere-specific localization of Moa1 and Rec8 regulates the orientation of kinetochores at meiosis-I.
D. Cohesin exhibits uniform distribution/localization pattern across the chromosomal length.
E. Polo/Cdc5 is a positive regulator of Separase, an endopeptidase that facilitates opening of the cohesin ring.
Which one of the following combination contains all correct statements?
Progression across G1/S boundary followed by entry into S-phase is promoted by the activation of which one of the following protein complexes?
To study the cell cycle progression for cultured mammalian cells, one would typically NOT utilize?
In Saccharomyces cerevisiae, DNA replication is tightly controlled, and DNA should replicate once per cell cycle. Choose the INCORRECT statement regarding why the cells do not re-replicate their DNA in the S-phase.
Column (A) lists enzymes involved in cell cycle and typical function in a particular cell cycle phase is listed in Column (B).
Which one of the following options represents the correct match between column A and column B?
In eukaryotes, DNA replication must occur with extreme accuracy and only once to prevent the damaging effects of gene amplification. The following statements were made regarding possible mechanisms involved in achieving tight regulation of DNA replication:
A. High APC/C activity in mitosis and early G₁ phase of the cell cycle that triggers the destruction of Cdt1 inhibitor geminin, thus allowing Cdt1 to be active in early G₁ to load helicases.
B. Activation of S-Cdks that regulate the phosphorylation of specific initiator proteins in the S-phase.
C. MCM helicase loads at the S-phase of the cell cycle, so that replication begins only at S-phase.
D. Cdc6 and Cdt1 bind to the origin recognition complex (ORC) and help in pre-replicative complex assembly only after mitosis.
Which one of the options has all correct statements?
Following statements were made about cell cycle regulation in eukaryotes:
A. Activity of maturation promoting factor (MPF) rises and falls in synchrony with the concentration of cyclin B.
B. Cdc25 phosphatase mediates removal of phosphate from the inhibitory tyrosine residue (Y15) to yield highly active MPF.
C. MPF specifically phosphorylates and depolymerizes lamin A and C, but not lamin B.
D. MPF phosphorylates H1 histone.
E. In Schizosaccharomyces pombe, overproduction of Wee1 protein decreases the length of G₂ phase and extends the period of M phase by functioning as a mediator of MPF activity.
Which one of the following represents the combination of correct statements?
Individual chromosomes are clearly seen during which phase of the cell cycle?
