Cell Cycle and M Phase Quiz

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Questions and Answers

What is the M phase of the cell cycle primarily characterized by?

Cell division through mitosis and cytokinesis (correct)

Preparation for the G1 phase

Protein synthesis and DNA replication

Cell growth and metabolic activities

During which phase does DNA replication occur?

G2 phase

M phase

S phase (correct)

G1 phase

Which statement best describes cytokinesis?

It is the DNA replication phase in the cell cycle.

It is the process that results in the separation of cytoplasm after mitosis. (correct)

It involves the division of the cell nucleus only.

It occurs only during the G1 phase of the cell cycle.

What occurs during the G1 phase of the cell cycle?

Most protein synthesis and basal metabolic activities Signup and view all the answers

How long does the M phase typically last?

About 1 hour Signup and view all the answers

What is a major function of the G2 phase?

Protein synthesis and pre-mitotic activities Signup and view all the answers

What is a key characteristic of interphase?

Cells undergo significant growth and metabolic activity. Signup and view all the answers

What structure is formed as the cleavage furrow deepens and leaves a bridge between daughter cells?

Midbody Signup and view all the answers

During which phase of the cell cycle does a cell grow and increase its volume while preparing for DNA replication?

G1 phase Signup and view all the answers

What is the primary role of myosin fibers in the cytokinesis process?

Delivering plasma membrane to the surface Signup and view all the answers

What characterizes cells that are in the irreversible G0 phase?

They are terminally differentiated and function indefinitely. Signup and view all the answers

What happens during the abscission stage of cell division?

The surfaces of the furrow fully fuse, splitting the cell. Signup and view all the answers

What is the fate of cells that fail to pass the G1-S checkpoint?

They enter an indefinite quiescent state (G0). Signup and view all the answers

What is the state of metabolic activities in cells that enter the G0 phase?

Metabolic activities are reduced to a minimum. Signup and view all the answers

Which of the following physiological processes occurs during the G1 phase?

RNA and protein synthesis Signup and view all the answers

What is the nature of quiescent cells that are in reversible G0 phase?

They can re-enter the cell cycle upon favorable conditions. Signup and view all the answers

What primarily distinguishes the G0 phase from other phases of the cell cycle?

It is a rest phase where cells do not divide. Signup and view all the answers

What is the primary function of G1 cyclins during the cell cycle?

Increasing in response to growth signals Signup and view all the answers

At what point do G1/S cyclins reach their peak levels?

During late G1 Signup and view all the answers

What is the role of the Maturation Promoting Factor (MPF)?

Facilitating the G2-M passage Signup and view all the answers

Which cyclins are associated with CDK2?

Cyclin A1 and E1 Signup and view all the answers

Which of the following proteins is a target of MPF?

Condensins Signup and view all the answers

What is a significant characteristic of p53 in cell cycle regulation?

It is a transcription factor activated by stress signals. Signup and view all the answers

What happens to M cyclins during the cell cycle?

They degrade during late metaphase. Signup and view all the answers

What is the primary role of G1/S cyclins in the cell cycle?

Regulating cell progression to S phase Signup and view all the answers

Which of the following statements about p53 is true?

It is composed of four chains of 393 amino acids. Signup and view all the answers

What is the function of the G1 cyclins at the G1 phase of the cell cycle?

Regulating cell size before replication Signup and view all the answers

What role does the Proline-rich Domain (PRD) play in the function of p53?

It allows p53 to interact with other transcription factors and coactivators. Signup and view all the answers

Which domain is primarily responsible for the sequence-specific recognition of DNA by p53?

Central DNA-binding Domain (DBD) Signup and view all the answers

How does MDM2 function in relation to p53 under physiological conditions?

It targets p53 for proteasomal degradation. Signup and view all the answers

Which of the following functions is NOT associated with the C-terminal Regulatory Domain (CTD) of p53?

Facilitating the formation of oligomeric complexes Signup and view all the answers

What initiates the activation of p53 in response to DNA damage?

Phosphorylation by ATR and ATM protein kinases Signup and view all the answers

Which type of cells do not undergo cell division?

Neurons Signup and view all the answers

What is the primary purpose of meiosis?

To produce gametes Signup and view all the answers

Which phase of the cell cycle can be as short as 30 minutes?

M phase in cleaving frog embryos Signup and view all the answers

Which process involves chromosome condensation?

Mitosis Signup and view all the answers

What is the role of cohesin during mitosis?

To hold sister chromatids together Signup and view all the answers

What structure forms from centrosomes during mitosis?

Mitotic spindle Signup and view all the answers

What process occurs when microtubules attach to kinetochores?

Chromosome congression Signup and view all the answers

Which cell category divides only under certain conditions?

Differentiated cells Signup and view all the answers

Which event primarily occurs during prophase of mitosis?

Chromosome condensation Signup and view all the answers

Study Notes

Cell Cycle

Two major phases based on cellular activities readily visible with a light microscope:
- M phase: Cell undergoes division (approx. 1 hour)
  - Mitosis: process of nuclear division, separating replicated DNA into two nuclei
  - Cytokinesis: process of dividing the cytoplasm of a cell in two. This happens after nuclear division in mitosis.
Interphase: Cell grows and performs metabolic activities (duration depends on cell type)
- G1: Most protein synthesis; basal metabolic activities
- S: DNA replication, histone synthesis, and chromosome duplication
- G2: Protein synthesis and pre-mitotic activities

Cell Cycle Variations

Cell cycle length varies significantly:
- 30 minutes in a cleaving frog embryo (lacking G1 and G2 phases)
- Days to weeks in most cells
- Several months in slowly growing tissues (e.g., mammalian liver)

Cell Categorization

Cells are categorized based on their capacity/frequency to grow and divide:
- Highly specialized cells: Do not undergo cell division (neurons, muscle, red blood cells, osteoclasts).
- Differentiated cells: Divide only upon induction (liver cells, lymphocytes).
- Unspecialized cells (stem cells): High mitotic activity (stem cells in various adult tissues, basal layer of epithelia).

Stem Cell Division

Stem cells may undergo asymmetric cell division
- One daughter cell remains uncommitted and similar to the parent cell
- The other daughter cell differentiates.

Mitosis (Cell Division)

Mitosis: Produces two daughter cells identical to the parental cell.
Serves to produce new cells throughout the body.
Billion divisions occur to produce complex multicellular organisms from a single cell (zygote).
Continuously occurs in developed organisms.
Renews tissues, regenerates damaged tissues, and maintains structural and functional homeostasis.

Mitosis Stages (detailed in subsequent sections)

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Cytokinesis (detailed in subsequent sections)

Separation of newly formed cells.
Involves processes initiated in late anaphase.

Interphase - G1 Phase

Cell grows and increases its volume.
Builds structures needed to support increased volume.
Metabolic activation (protein and RNA synthesis).
Duplication of centrosomes and cytoplasmic organelles.
Controls the extracellular environment and cell size to support DNA replication.

Interphase - G0 Phase

Some cells can stop cycling for an indefinite time (quiescent state).
This is due to unfavorable environmental conditions.
Arrests replication, metabolic rate reduces.
Can be reversible or irreversible.
May retain ability to divide upon changes in environmental conditions.
Terminally differentiated cells: Progress towards specific function (e.g. neurons, muscle), permanently reside in G0.
Senescent cells: Damaged DNA; enter G0 to prevent damage propagation.

Interphase - S Phase

Each chromosome duplicates its chromatid, becoming 'di-chromatid'.
Histone synthesis occurs.
Free histones incorporated into new nucleosomes.
Chromatin domains re-establish (maintaining epigenetic regulation scheme).
DNA checked for damage.

Interphase - G2 Phase

Cells grow rapidly, increasing in size.
Active protein synthesis occurs.
Duplicated chromosomes are checked for errors.
Double-strand breaks are repaired.
Prepares for mitosis.

Cell Cycle Regulation

Cell controls a wide variety of information packages (integrity and activity of molecules, organelles, chemical signals, mechanical signals).
Decisions about progress in the cell cycle are made based on these signals.
Decisions occur at specific checkpoints.

Cell Cycle Checkpoints (detailed in subsequent sections)

G1-S checkpoint : The cell verifies the availability of growth factors, nutrients, and enzymes before starting S phase.
G2-M checkpoint : the cells checks that DNA synthesis is complete and correct. If DNA contains error or damages, or is incomplete, the gate is closed and mitosis cannot start.
Mitotic checkpoint (spindle checkpoint) : at the end of metaphase, the cell checks that all kinetochores are correctly attached to sister chromatids on the metaphase plate

Cyclins and Cyclin-Dependent Kinases (CDKs)

Regulation of passage between cell cycle stages.
CYCLIN: regulatory subunit
CYCLIN-dependent KINASE (CDK): transfers phosphate groups, activating specific protein substrates.

Cyclins and CDKS activity control

Activity of kinases is regulated by cyclin levels, which fluctuate throughout the cell cycle.
Multiple cyclins and CDKs expressed at different phases of the cell cycle.
They regulate various checkpoints in the cell cycle.

p53 Role in Cell Cycle Regulation

p53 is a transcription factor essential for controlling cell cycle processes.
Important for responding to cellular stresses (e.g., DNA damage).
Activated p53 regulates production of proteins involved in DNA repair, apoptosis, and cell-cycle arrest.
p53 is activated when cellular stress signals are present, like DNA damage and nutrients and is deactivated when the cell's health is good.

Meiosis

Reductional cell division, distributing replicated homologous chromosomes.
Two sequential divisions ("Meiosis I" and "Meiosis II") without an intervening DNA replication phase.
- Meiosis I: Separates homologous chromosomes.
- Meiosis II: Separates sister chromatids.

Meiosis I Subphases

Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis

Meiosis Recombination

Crossing over occurs during prophase I, leading to new combinations of maternal and paternal alleles.

Meiosis I Stages (detailed in subsequent sections)

Prophase I
Metaphase I
Anaphase I
Telophase I

Consequences of Meiotic Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate properly during meiosis I or II.
Can result in aneuploidy (abnormal number of chromosomes) in offspring.
Some resulting conditions have distinct human karyotype abnormalities that can be seen using karyotyping.

Human Aneuploidies

Trisomy 21 (Down's syndrome)
Trisomy 18 (Edwards' syndrome)
Trisomy 13 (Patau's syndrome)
47, XXY (Klinefelter's syndrome)
45, X (Turner's syndrome)

Meiosis in Vertebrates

Meiosis occurs in gonads to produce gametes.
Male: Spermatogonia undergo meiosis to form spermatozoa.
Female: Oogonia undergo meiosis to form oocytes.

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Description

Test your understanding of the cell cycle, focusing on the M phase and its key processes. This quiz covers various phases, including G1, G2, cytokinesis, and more. Perfect for biology students wanting to solidify their knowledge of cell division.