Biological Science Module 3 - DNA & Chromosomes

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Questions and Answers

What is the primary stage where most cells spend their time before mitosis?

Anaphase

Interphase (correct)

Telophase

Cytokinesis

How can external factors influence cell division?

Through changes in temperature

By triggering the release of growth hormones (correct)

By inhibiting nutrient absorption

Only through genetic mutations

What can result from an excessive amount of human growth hormone (HGH)?

Dwarfism

Cellular senescence

Gigantism (correct)

Cell starvation

What is the purpose of checkpoints in the cell division process?

To guarantee daughter cells replicate accurately Signup and view all the answers

What is the outcome of a problem with chromosome duplication during cell division?

Development of mutations in offspring cells Signup and view all the answers

How do plant cells differ from animal cells during cytokinesis?

They create a cell plate from vesicles Signup and view all the answers

Which scenario can impede cell division?

Cell congestion Signup and view all the answers

What structural change occurs between daughter cells in plant cells?

A new cell wall is developed Signup and view all the answers

What structural change occurs during DNA replication that is key to chromosome formation?

Sister chromatids are formed Signup and view all the answers

What is the primary function of the G2 phase in the cell cycle?

Energy stores are replenished and proteins are synthesized Signup and view all the answers

Which statement accurately describes what happens during prophase?

Chromatin condenses into visible chromosomes Signup and view all the answers

Which phase of the cell cycle involves the disassembly of the nuclear envelope?

Prometaphase Signup and view all the answers

During which phase do cell organelles duplicate and the cytoskeleton get dismantled?

G2 phase Signup and view all the answers

What is the purpose of the mitotic spindle during karyokinesis?

To organize and separate chromosomes Signup and view all the answers

Which of the following correctly describes a homologous pair of chromosomes?

Each chromosome is derived from the same parent Signup and view all the answers

What distinguishes the stages of the mitotic phase?

Alignment and separation of chromosomes Signup and view all the answers

What occurs at anaphase that is crucial for the cell cycle to progress?

Kinetochores are anchored to spindle fibers. Signup and view all the answers

Which is a consequence of malfunctioning cell cycle regulators?

Uncontrolled cell division. Signup and view all the answers

How does the p53 gene contribute to the regulation of the cell cycle?

It senses DNA damage and activates checkpoint genes. Signup and view all the answers

What may result from atypical hyperplasia?

Uncontrolled cell division leading to cancer. Signup and view all the answers

What is unique about prokaryotic cell division compared to eukaryotic cell division?

It utilizes binary fission for reproduction. Signup and view all the answers

What is the primary cause of metastasis in malignant cells?

Decreased ability to adhere to surrounding cells. Signup and view all the answers

Why does the single circular DNA chromosome in prokaryotes allow for faster DNA replication?

It simplifies the replication process without coordinating multiple chromosomes. Signup and view all the answers

Which factor primarily classifies a situation as cancer?

Unregulated and excessive cell division. Signup and view all the answers

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

To ensure favorable conditions for cell division Signup and view all the answers

What happens if a cell does not meet the conditions at the G1 checkpoint?

The cell may enter the G0 phase or halt the cycle Signup and view all the answers

Which of the following is NOT a factor that the G1 checkpoint assesses?

Oxygen levels Signup and view all the answers

How do positive regulators affect the cell cycle, according to the content?

Their excessive activity can lead to cancer. Signup and view all the answers

What role do inhibitors play in the context of cell division?

They inhibit cell division under unfavorable situations. Signup and view all the answers

Where do the Golgi membranes merge in the process of forming the new wall?

Into the plasma membrane Signup and view all the answers

What mechanism is suggested for cells when encountering issues at the G1 checkpoint?

They can remain inactive in the G0 phase. Signup and view all the answers

When does the cell cycle have checkpoints to prevent damaged cells from proliferating?

At three crucial points during the cycle Signup and view all the answers

What does the G2 checkpoint evaluate before allowing entry into mitosis?

Protein stores and cell size Signup and view all the answers

What initiates the process of mitosis?

The activation of cyclin-dependent kinases (CDKs) Signup and view all the answers

How many mutations do the majority of cancer cells have, according to research?

At least 60 mutations Signup and view all the answers

What role do tumor suppressor genes play in cell division?

They inhibit cell division and trigger apoptosis Signup and view all the answers

During which phase of mitosis does the M checkpoint occur?

Metaphase Signup and view all the answers

Why can cancer cells proliferate in a culture without growth factors?

They produce their own growth-stimulating proteins Signup and view all the answers

What can cause the inactivity of tumor suppressor genes?

Mutations linked to cancer Signup and view all the answers

What does the M checkpoint ensure during mitosis?

Sister chromatids are properly anchored to spindle microtubules Signup and view all the answers

Study Notes

DNA and Chromosome Structure

Chromosomes condense during cell division, ensuring equal distribution of genetic material during karyokinesis.
Homologous pairs include chromosomes inherited from each parent, represented by different colors (e.g., red and blue).
Sister chromatids form during DNA replication, characterized by an "X" shape.

Cell Cycle Phases

G2 Phase: Cells replenish energy, synthesize proteins for chromosome manipulation, and duplicate organelles. Cytoskeleton dismantling occurs to prepare for mitosis.
Transition to mitosis requires completion of final preparations in G2.

Mitotic Phase Steps

Prophase: Chromatin condenses to form visible chromosomes; mitotic spindle begins forming; the nuclear envelope starts disintegrating.
Prometaphase: Complete breakdown of the nuclear envelope allows spindle fibers to attach to kinetochores of chromosomes.

Cell Division and Regulation

Karyokinesis is the process where parent cells divide into two offspring cells; cells are designed to survive as long as the organism.
Cells typically spend time in interphase, a non-dividing stage, before mitosis.
External factors, such as growth hormones, can initiate cell division; human growth hormone (HGH) must be in balance to avoid disorders like gigantism or dwarfism.

Cytokinesis Variations

In plant cells, a cleavage furrow is formed, and a new cell wall (cell plate) is constructed from vesicle congregation from the Golgi apparatus.
Enzymes utilize glucose to build new walls, which fuse with existing cell membranes.

Internal Cell Cycle Checkpoints

G1 Checkpoint: Assesses cell size, energy reserves, and DNA integrity before commitment to division. Unfavorable conditions may lead to a G0 phase (inactive) or pause in the cycle.
G2 Checkpoint: Ensures conditions are right for mitosis, evaluating protein levels, cell size, and chromosome integrity before entering the mitotic phase.
M Checkpoint: Verifies that all sister chromatids are properly attached to spindle fibers before anaphase; prevents early cycle initiation.

Cancer Mechanisms

Uncontrolled cell division, a hallmark of cancer, often results from mutations in genes regulating the cell cycle, such as the p53 gene.
Tumor suppressor genes prevent excessive division; mutations in both gene copies can lead to uncontrolled growth.
Cancer development can begin with atypical hyperplasia due to excessive division from mutations.

Prokaryotic Cell Division

Prokaryotic cells feature a simple division process known as binary fission, facilitated by a single circular DNA chromosome.
Absence of a nucleus and multiple chromosomes streamlines DNA replication, negating the need for intricate mitosis.
Prokaryotic division method promotes swift reproduction, contrasting with eukaryotic cell division complexities.

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Description

This quiz covers key concepts from Module 3 of Biological Science, focusing on the structure and function of DNA and chromosomes. Students will explore topics like homologous chromosomes and chromosomal division as part of their first semester curriculum for 2024-2025.