A. The polar orientation of the cell for the division into two daughter cells established
B. The nuclear envelop breaks down
C. The nuclear envelop disappears
D. The diffuse chromatin fibers condense and begins to form dense chromosome
Choose the correct answer from the options given below:
Mitosis Prophase Stage: Understanding Cell Division Steps
Mitosis is a fundamental process in cell biology, responsible for growth and repair, where a single cell divides into two genetically identical daughter cells. The prophase stage is the initial phase of mitosis, setting the stage for chromosome segregation.
Key Events Described in Prophase
Let's look at the descriptions provided for each step:
- A. The polar orientation of the cell for the division into two daughter cells established: This describes the alignment and organization of the cell structures, particularly the spindle apparatus, which guides chromosome movement.
- B. The nuclear envelop breaks down: This refers to the initial dismantling of the membrane surrounding the cell's nucleus.
- C. The nuclear envelop disappears: This signifies the complete removal of the nuclear envelope, freeing the chromosomes into the cytoplasm.
- D. The diffuse chromatin fibers condense and begins to form dense chromosome: This is the process where the cell's genetic material, initially dispersed as chromatin, coils up tightly to become visible chromosomes.
The Correct Sequence of Prophase Events
The question asks for the correct sequence of these steps during the prophase stage of mitosis. Following the provided correct answer, the sequence is B, C, D, A.
This sequence involves:
- Starting with the breakdown of the nuclear envelope (B).
- Followed by its complete disappearance (C).
- Then, the condensation of chromatin fibers into chromosomes (D).
- And finally, the establishment of polar orientation for cell division (A).
This specific order represents the progression through key events as identified for the mitosis prophase stage.
Important Questions from Cell Division and Cell Cycle
During cell cycle, entry in the S-phase is tightly regulated. This is possible because:
A. APC/C promotes ubiquitination of S-phase cyclins and mitotic cyclins, marking them for proteolyses at the mitotic exit.
B. Cyclin B1 helps in the activation of S-phase CDKs only in late G1.
C. As mitotic CDK activity declines in late mitosis, cdc14 phosphatase activates APC/C by dephosphorylating Cdh1, thus promoting formation of APC/CCdh1
D. Securin keeps S-phase cyclins in inactive state till late G1.
Which one of the options represents all correct statements?
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?
The table below lists cell cycle regulatory proteins and their known functions
Which one of the following options represents the correct match between cell cycle regulatory proteins with their known functions?Cell Cycle regu latory proteins Function A Cdk-activating kinase (CAK) (i) Suppresses G1/S-Cdk and S-Cdk activation in G1; helps cells withdraw from cell cycle when they terminally differentiate; phosphorylation by Cdk2 triggers its ubiquitylation by SCF. B Wee1 kinase (ii) Suppresses G1/S-Cdk and S-Cdk activities following DNA damage C p27 (mammals) (iii) Phosphorylates inhibitory sites in Cdks: primarily involved in suppressing Cdk1 activity before mitosis D p21 (mammals) (iv) Phosphorylates an activating site in Cdks Following statements were made about the characteristics of cyclin proteins:
A. Synthesis of M-cyclin is dependent on the cyclin mRNA that is newly transcribed after every cycle.
B. Destruction of M-cyclin toward the end of mitosis is driven by ubiquitin independent proteolytic system.
C. G1 cyclins can be activated by mitogenic factors.
D. Retinoblastoma (Rb) is a key target of the activated cyclin D - Cdk 4/6 complex.
E. While cyclin A1 expression is ubiquitous, cyclin A2 expression is restricted to the germ cell lineages.
Which one of the following options contains a combination of all correct statements?
To test the impact of cAMP on protein kinase A conformation in cells, an investigator made FRET biosensor by fusing two fluorescent proteins at the N-and C-terminus of protein kinase A. In the absence of cAMP in the cellular milieu, no FRET signal was detected. However, upon cAMP addition, a strong emission at 530 nm was observed. What could be the best configuration of fluorophores that were used by the investigator?
