Cell Cycle and Division Quiz

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Questions and Answers

What happens during the G2 stage of interphase?

DNA replication occurs.

Proteins needed for cell division are synthesized. (correct)

The cell undergoes apoptosis.

The cell doubles its organelles.

Which stage of the cell cycle is primarily focused on DNA replication?

S Stage (correct)

G2 Stage

G1 Stage

M Stage

What is the role of the G1 checkpoint in the cell cycle?

To trigger apoptosis when necessary.

To ensure adequate nutrients and cell size before DNA synthesis. (correct)

To coordinate DNA replication.

To assess the readiness for mitosis.

What distinguishes mitosis from meiosis?

Mitosis produces genetically identical daughter cells; meiosis produces genetically varied cells. Signup and view all the answers

What occurs during cytokinesis?

The cytoplasm divides to form two cells. Signup and view all the answers

What is the consequence of failing the cell cycle control mechanisms?

Unrestricted cell growth and potentially cancer. Signup and view all the answers

During which phase of interphase does the cell prepare for DNA synthesis by accumulating necessary materials?

G1 Stage Signup and view all the answers

What defines apoptosis in the context of the cell cycle?

Programmed cell death occurring when cells are damaged. Signup and view all the answers

What is the primary purpose of cytokinesis during cell division?

To divide the cytoplasm and organelles Signup and view all the answers

What is the outcome of meiosis I?

Two haploid cells with 23 chromosomes each Signup and view all the answers

During which stage of meiosis does crossing over occur?

Prophase I Signup and view all the answers

Which statement accurately describes anaphase I?

Chromatids are separated and move to opposite poles. Signup and view all the answers

What characterizes meiosis II when compared to mitosis?

It involves the separation of sister chromatids. Signup and view all the answers

In which stage do chromosomes become arranged along the metaphase plate during meiosis II?

Metaphase II Signup and view all the answers

How many chromosomes will each daughter cell contain after completing telophase II of meiosis?

23 chromosomes Signup and view all the answers

What happens to the nuclear membrane during prophase II?

It breaks down and remains absent until telophase II. Signup and view all the answers

What are sister chromatids?

Identical parts of a chromosome connected by a centromere Signup and view all the answers

What occurs during prophase of mitosis?

Chromosomes condense and become visible Signup and view all the answers

What is the role of centrosomes during cell division?

To organize and anchor spindle fibers Signup and view all the answers

How many chromosomes do humans have?

46 in 23 pairs Signup and view all the answers

During which phase do sister chromatids separate?

Anaphase Signup and view all the answers

What is the metaphase plate?

The region in the center where chromosomes align during metaphase Signup and view all the answers

Which statement is true about sex chromosomes in humans?

Females have two X chromosomes Signup and view all the answers

What happens to spindle fibers during telophase?

They disappear as the nuclear envelope reappears Signup and view all the answers

Study Notes

Cell Cycle Overview

The cell cycle consists of events for cell growth and division: Interphase and Cell Division.
Interphase: the stage where the cell prepares for division, growing larger and replicating DNA and organelles.

Interphase Stages

G1 Phase:
- Cells double organelles and gather materials for DNA synthesis.
S Phase:
- DNA replication occurs, resulting in chromosomes composed of two identical sister chromatids.
G2 Phase:
- Proteins necessary for cell division are synthesized.

Cell Division

Includes Mitosis and Cytokinesis.
Mitosis:
- Nuclear division where one copy of DNA is distributed to daughter cells.
Cytokinesis:
- Cytoplasmic division resulting in two new cells, each with organelles.

Checkpoints in Cell Cycle

Controlled by checkpoints:
- G1 checkpoint, G2 checkpoint, and the M phase checkpoint.
- Failure in checkpoints may lead to uncontrolled growth and cancer.

Chromosomes Basics

Genetic material resides in the nucleus, packaged as chromosomes (DNA + proteins = chromatin).
In non-dividing cells, chromatin appears as a tangled mass; during division, it condenses into visible chromosomes made of sister chromatids.

Human Chromosome Count

Humans have 46 chromosomes (23 pairs).
Autosomes: 22 pairs shared by all and one pair of sex chromosomes determining gender (XX in females, XY in males).

Mitosis Phases

Prophase:
- Centrosomes duplicate, spindle fibers form, nuclear envelope fragments, and visible chromosomes condense.
Prometaphase:
- Spindle fibers attach to centromeres; chromosomes further condense.
Metaphase:
- Chromosomes align at the metaphase plate attached to spindle fibers.
Anaphase:
- Sister chromatids separate and are pulled to opposite poles, now considered individual chromosomes.
Telophase:
- Chromosomes reach poles, re-condense to chromatin, and the nuclear envelope and nucleolus reappear.

Cytokinesis Mechanism

Actin filaments form a contractile ring, pinching the cell membrane inwards to create two daughter cells.
Each daughter cell is diploid (2n) with 46 chromosomes, genetically identical to the parent cell.

Meiosis Overview

Meiosis: reduction division with two successive cell divisions (Meiosis I and II) without interphase.
The parent cell is diploid (2n) with homologous chromosomes.

Meiosis I Phases

Prophase I:
- Homologous chromosomes form tetrads and may undergo crossing over, leading to genetic variation.
Metaphase I:
- Homologous chromosome pairs align at the metaphase plate.
Anaphase I:
- Homologous chromosomes are pulled toward opposite poles, each still consisting of two chromatids.
Telophase I:
- Each pole receives a haploid set of chromosomes, nuclear membranes form around each set.

Meiosis II Phases

Similar to mitosis, involves the division of the two haploid cells produced in Meiosis I.
Prophase II:
- Centrioles move to poles, spindle fibers form, and chromosomes condense.
Metaphase II:
- Chromosomes align along the metaphase plate.
Anaphase II:
- Centromeres divide, and sister chromatids move to opposite poles.
Telophase II:
- Chromosomes elongate, nuclear membranes form, resulting in four haploid daughter cells (n) with half the original chromosome number.

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Description

Test your knowledge on the stages of the cell cycle and the phases of mitosis and meiosis. This quiz covers the purpose of each stage and the differences between mitosis and meiosis, providing a comprehensive overview of cellular processes. Challenge yourself and enhance your understanding of cell division mechanics.