Biology Cell Division Overview

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Questions and Answers

What is the primary function of apoptosis during embryogenesis?

To strengthen tissue structure

To promote cell division

To eliminate excess cells (correct)

To increase cell size for growth

What condition results from excessive apoptosis in tissues?

Atherosclerosis

Tumor growth

Neurodegeneration (correct)

Hyperplasia

What role does apoptosis play in adults?

It prevents any form of cell death

It is only involved in cancer prevention

It solely enhances cell multiplication

It contributes to tissue remodeling by eliminating unneeded cells (correct)

What is a consequence of insufficient apoptosis in tissues?

Uncontrolled cell growth (B) Signup and view all the answers

During which physiological phase does apoptosis contribute to the involution of the mammary gland?

Non-pregnant, non-lactating state (B) Signup and view all the answers

What occurs during the S phase of the cell cycle?

Chromosome duplication takes place. (A) Signup and view all the answers

During which phase of the cell cycle does the cell perform most of its normal physiological functions?

G1 Phase (C) Signup and view all the answers

Which of the following best describes mitosis?

A process resulting in two identical daughter cells. (A) Signup and view all the answers

What is the primary role of checkpoints in the cell cycle?

To regulate the transition between different phases of the cycle. (B) Signup and view all the answers

Which type of reproduction leads to genetically identical daughter cells?

Asexual reproduction through binary fission. (A) Signup and view all the answers

What triggers the start of the cell division process?

When the cell's size is appropriate and has sufficient energy stores (D) Signup and view all the answers

What is a unique feature of meiosis compared to mitosis?

It produces genetic variation in offspring. (C) Signup and view all the answers

What happens to the DNA during binary fission in prokaryotes?

DNA is replicated and then distributed to daughter cells. (B) Signup and view all the answers

During which phase of the cell cycle does DNA replication occur?

S phase (C) Signup and view all the answers

Which phase of the cell cycle is known as the primary growth phase?

G1 phase (A) Signup and view all the answers

What characterizes apoptosis?

It is a programmed process of cell death. (A) Signup and view all the answers

What does the term 'karyokinesis' refer to?

The division of the nucleus (B) Signup and view all the answers

In which stage of mitosis do the chromosomes align at the cell's equator?

Metaphase (A) Signup and view all the answers

Which of the following structures is synthesized during the G2 phase to prepare for cell division?

Centrioles (D) Signup and view all the answers

Which type of cells typically do not undergo mitosis?

Nerve cells (B) Signup and view all the answers

What happens during the Anaphase stage of mitosis?

Sister chromatids are pulled apart to opposite poles (D) Signup and view all the answers

What occurs during telophase of mitosis?

Chromosomes reappear as chromatin. (A) Signup and view all the answers

What is the main role of cytokinesis?

To divide the cytoplasm into two daughter cells. (B) Signup and view all the answers

What structure aids in forming the cleavage furrow during cytokinesis in animal cells?

Actin and myosin contractile ring (C) Signup and view all the answers

Which of the following molecules are involved in the regulation of the cell cycle?

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

What is the function of the checkpoints in the cell cycle?

To monitor and regulate the cell cycle's progression. (D) Signup and view all the answers

During which phase of the cell cycle does chromatin condense into chromosomes?

Prophase (A) Signup and view all the answers

What happens to the nucleolus during telophase?

It becomes visible again. (B) Signup and view all the answers

What is the outcome of uncontrolled cell division?

Cancer development (A) Signup and view all the answers

What is the primary function of the G1 checkpoint in the cell cycle?

To make sure everything is prepared for DNA replication (C) Signup and view all the answers

Which checkpoint is responsible for ensuring that the cell is ready to complete cell division?

Metaphase checkpoint (A) Signup and view all the answers

What outcome results from a loss of control in the cell cycle?

Tumor formation (A) Signup and view all the answers

How does a defective p53 gene affect a cell's response to the cell cycle?

It prevents the cell from receiving signals (B) Signup and view all the answers

What is a key difference between normal cells and cancer cells regarding DNA replication?

Cancer cells experience mutations during DNA replication (B) Signup and view all the answers

Which statement best describes necrosis?

Unregulated cell death of masses of cells (A) Signup and view all the answers

In the context of cancer, what role does the p53 protein play during the cell cycle?

It halts cell division when damaged DNA is detected (C) Signup and view all the answers

What happens to cell communication in cancer cells compared to normal cells?

Cancer cells do not communicate with each other (D) Signup and view all the answers

Study Notes

Introduction

Organisms need new cells for growth, replacement, and repair.
New cells are formed through asexual reproduction, where one cell divides into two identical cells (e.g., mitosis and binary fission)
Sexual reproduction involves the joining of two cells (e.g., egg and sperm) to create a new cell (zygote).

Cell Division

Prokaryotes: Division occurs through binary fission.
- Prokaryotes have a single circular DNA molecule.
- DNA replicates, and each copy attaches to the cell membrane.
- The cell pulls apart, separating the DNA copies.
- Two identical daughter cells are formed.
Eukaryotes: Division occurs when the cell reaches a certain size and energy stores are sufficient.
- The process is controlled by the cell cycle.

The Cell Cycle

The cell cycle represents the stages a cell goes through from division to the next division.
It consists of three phases:
- Interphase: The period between cell divisions, where the cell grows and copies its DNA.
- Mitosis: Nuclear division, where the replicated chromosomes are separated into two daughter nuclei.
- Cytokinesis: The division of the cytoplasm, resulting in two daughter cells.

Interphase

G1 (Growth 1) Phase:
- Cell grows and increases organelle production.
- Prepares for DNA replication.
S (Synthesis) Phase:
- DNA amount is doubled.
- Chromosomes are replicated to form sister chromatids.
G2 (Growth 2) Phase:
- Cell continues to grow and produce proteins and organelles needed for cell division.
- Prepares for mitosis.

Mitosis

Nuclear division that occurs in eukaryotes.
Consists of four phases:
- Prophase:
  - Chromatin condenses into chromosomes.
  - Nucleolus and nuclear membrane disappear.
  - Mitotic spindle forms from centrioles.
- Metaphase:
  - Chromosomes align at the cell equator.
  - Centromeres are attached to kinetochore fibers.
- Anaphase:
  - Sister chromatids are pulled apart by spindle fibers.
  - Each pole receives a complete set of original genes.
- Telophase:
  - Chromosomes reappear as chromatin.
  - Nuclear envelope reforms around each set of chromosomes.
  - Nucleolus becomes visible.
  - Spindle breaks apart.

Cytokinesis

The division of the cytoplasm.
Involves the formation of a cleavage furrow in animal cells.
Acts to separate the daughter cells after mitosis.

Regulation of the Cell Cycle

Aims to prevent uncontrolled cell division.
Controlled by cyclins and cyclin-dependent kinases (CDKs).
- They form heterodimers that activate or deactivate target proteins.
Checkpoints: Monitor and regulate the cell cycle to ensure proper progression.
- G1 Checkpoint: Ensures cell is ready for DNA replication.
- G2 Checkpoint: Ensures cell is ready for mitosis.
- Metaphase Checkpoint: Ensures all chromosomes are attached to spindle fibers before anaphase.

Uncontrolled Cell Division

Uncontrolled cell division leads to tumor formation.
Defective p53 gene can cause loss of cell cycle control.
Cancer cells lack p53 function, leading to uncontrolled growth and multiplication.

Cell Death

Necrosis:
- Unregulated cell death due to injury, disease, or blood supply failure.
Apoptosis:
- Programmed cell death, a regulated process for removing unwanted cells.

Necrosis vs Apoptosis

Necrosis:
- Uncontrolled cell death.
- Causes cell swelling and lysis.
- Can damage surrounding tissues.
Apoptosis:
- Controlled cell death.
- Involves cell shrinkage and fragmentation.
- Minimizes damage to surrounding tissues.

Apoptosis in Physiological Situations

Important for embryogenesis, morphogenesis, and tissue remodeling.

Apoptosis in Adults

Plays a role in tissue remodeling and hormone-regulated processes.

Apoptosis in Disease

Too much apoptosis: Tissue atrophy, neurodegeneration.
Too little apoptosis: Hyperplasia, atherosclerosis.

Why Cell Division is Important

Cell division allows for growth and repair, enabling organisms to maintain their size and function.
Cell division is more efficient than cell enlargement for maintaining cellular function.
Larger cells have a lower surface area to volume ratio, making it difficult for nutrients and wastes to be exchanged efficiently.
Cell division maintains a more optimal surface area to volume ratio, ensuring efficient function.

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Description

Explore the fascinating processes of cell division in organisms. This quiz covers asexual reproduction, binary fission in prokaryotes, and the cell cycle in eukaryotes. Test your understanding of how cells grow, replace, and repair themselves.