Cell Cycle & Cell Death Overview

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Questions and Answers

What is the primary function of the Gap 1 phase (G1 phase) in the cell cycle?

Active RNA and protein synthesis (correct)

Cytoplasmic division

DNA duplication

Chromosome separation

During which phase of the cell cycle do cells contain 46 identical pairs of chromosomes?

Gap 2 phase

Gap 1 phase

Synthesis phase (correct)

Mitosis

What distinguishes necrosis from apoptosis in cell death?

Apoptosis leads to cell swelling

Necrosis is programmed cell death

Apoptosis is an uncontrolled process

Necrosis typically results in inflammation (correct)

What happens to cells that are terminally differentiated in the cell cycle?

They leave the cycle permanently Signup and view all the answers

What characterizes the Gap 2 phase (G2 phase) of the cell cycle?

Synthesis of cytoplasmic materials Signup and view all the answers

How does the cell's size change during the Gap 1 phase (G1 phase)?

The cell grows to nearly the size of the mother cell Signup and view all the answers

Which of the following is not a phase of interphase?

Cytokinesis Signup and view all the answers

Which statement about the cell cycle is true regarding non-dividable cells?

They exit the cycle permanently or for extended periods Signup and view all the answers

What is the primary purpose of the G2/M checkpoint in the cell cycle?

To verify that DNA replication is complete Signup and view all the answers

Which stage of cell development involves an increase in the number of cells through mitotic divisions?

Growth Signup and view all the answers

What characterizes necrosis compared to apoptosis?

Necrosis leads to cell swelling and bursting, apoptosis is a controlled process Signup and view all the answers

Which proteins regulate progression through the cell cycle?

Cyclins and cyclin-dependent kinases (CDKs) Signup and view all the answers

What is the role of the metaphase spindle checkpoint?

To guarantee proper chromosome segregation Signup and view all the answers

Which of the following is NOT a major stage of cell development?

Migration Signup and view all the answers

Which of these statements is true regarding the cell cycle duration?

Cell cycles vary between 10 to 30 hours depending on the cell type Signup and view all the answers

What is the significance of integration in cell development?

To ensure harmony between growth and differentiation Signup and view all the answers

Study Notes

Cell Cycle & Cell Death

Learning Objectives:
- Define the cell cycle and illustrate the phases.
- Explain the events occurring in each phase.
- Recognize the relationship between cell differentiation and the cell cycle.
- Differentiate between cell death by apoptosis and necrosis.
- Define apoptosis and its characteristics.

The Cell Cycle

Definition: A sequence of events during cell division and rest (interphase), producing new cells.
Periods:
- Interphase: Gap 1 (G1), Synthesis (S), and Gap 2 (G2) phases.
- Mitosis: Nucleus (karyokinesis) and cytoplasm (cytokinesis) division.

Stages of Cell Cycle

G₁ (Gap 1) Phase:
- Interval between mitosis and synthesis.
- Chromosomes are s-chromosomes (46 chromosomes).
- The nucleus shows no increase in DNA content.
- Active RNA and protein synthesis, growth.
- Cells either divide again or enter a non-dividing state (G₀).
S (Synthesis) Phase:
- DNA molecules and centrioles duplicate.
- The cell contains 46 identical pairs of chromosomes (often called double chromosomes).
G₂ (Gap 2) Phase:
- Period between synthesis and mitosis (relatively short).
- Cells prepare for mitotic division, synthesize cytoplasmic material (e.g., proteins).
- Organelles increase in number.
- Chromosomes are double chromosomes (double the DNA compared to G₁).
- Most cells transition from G₂ to the next mitosis.
Mitosis (M):
- Chromosomes shorten, align in the cell's middle, then separate.
- Creates two genetically identical daughter cells.
- Cell cycle completion time is 10-30 hours, and the cycle begins again after mitosis completion.
- Includes stages Prophase, Metaphase, Anaphase, Telophase.

Cell Cycle Checkpoints

Checkpoints: Control points to ensure each phase is completed.
Stages:
- Start (restriction) checkpoint (before S phase)
- G₂/M checkpoint (ensuring DNA replication is complete)
- Metaphase checkpoint (ensuring all chromosomes are correctly attached to the mitotic spindle).
Control Mechanism: Cyclin-dependent kinases (CDKs) and cyclins regulate the entire cycle.

Cell Development

Stages:
- Growth: Increase in mass (size or number of cells).
- Differentiation: Developing new features and functions.
- Integration: Growth and differentiation are balanced, creating tissues and organs.

Cell Death

Necrosis:
- Cell death due to external factors (e.g., injury, toxins).
- The cell swells, chromatin clumps, and cytoplasm gets weakly stained.
- The cell bursts, releasing contents.
Apoptosis:
- Normal cell death due to internal factors (programmed cell death).
- A rapid, highly regulated process that eliminates defective or unneeded cells.
- The cell shrinks, DNA is condensed and degraded.
- Forms apoptotic bodies, which are then removed by phagocytes (cells specialized for debris removal).

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Description

This quiz covers the cell cycle and the mechanisms of cell death, including apoptosis and necrosis. You will explore the phases of the cell cycle, the events in each phase, and their relationship with cell differentiation. Test your understanding of these critical biological processes.