Biology Chapter 2.1 on Cell Cycle and Chromosomes

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Questions and Answers

What does the term diploid (2n) refer to in animals?

  • Cells that are in a resting state
  • Cells that contain two copies of each chromosome (correct)
  • Cells that are involved in sexual reproduction
  • Cells that contain one copy of each chromosome

Germ cells are haploid and carry two copies of each chromosome.

False (B)

What is the primary purpose of the G1 stage in the cell cycle?

Cells create organelles for energy and protein production.

During interphase, individual chromosomes are in a less condensed form known as __________.

<p>chromatin</p> Signup and view all the answers

Match the following stages of the cell cycle with their descriptions:

<p>G1 = Cells grow and create organelles S = DNA synthesis occurs G2 = Further growth and preparation for mitosis M = Mitosis and division of the cell</p> Signup and view all the answers

What phase of the cell cycle is collectively known as interphase?

<p>G1, S, G2 (C)</p> Signup and view all the answers

The cell spends about 90% of its time in interphase during the cell cycle.

<p>True (A)</p> Signup and view all the answers

What happens to cells in the G0 stage?

<p>They are not preparing for division and are performing their normal functions.</p> Signup and view all the answers

Passage from G1 to S stage in the cell cycle is governed by a __________.

<p>restriction point</p> Signup and view all the answers

What is the main consequence of derangements of the cell cycle?

<p>Cancer formation (A)</p> Signup and view all the answers

What is the primary role of p53 in the cell cycle?

<p>To repair damaged DNA (A)</p> Signup and view all the answers

Sister chromatids are formed during the G1 phase of the cell cycle.

<p>False (B)</p> Signup and view all the answers

What happens during the G2 stage of the cell cycle?

<p>Quality control checkpoint occurs, ensuring adequate size and organelle replication.</p> Signup and view all the answers

The process of __________ involves the separation of sister chromatids.

<p>anaphase</p> Signup and view all the answers

Match the cell cycle phase with its main event:

<p>G1 = Cell growth and organelle duplication S = DNA replication G2 = Preparation for mitosis M = Mitosis and cytokinesis</p> Signup and view all the answers

Which of the following statements about mitosis is correct?

<p>Chromosomes align during metaphase. (C)</p> Signup and view all the answers

Cancer cells often complete the cell cycle without proper DNA integrity checks.

<p>True (A)</p> Signup and view all the answers

What is the significance of the centromere?

<p>It binds sister chromatids together.</p> Signup and view all the answers

The accumulation of mutations in cells can lead to the formation of __________.

<p>tumors</p> Signup and view all the answers

Which of the following best describes oncogenes?

<p>Genes that promote cell division when mutated (B)</p> Signup and view all the answers

What happens to the nuclear membrane during prophase?

<p>It dissolves (A)</p> Signup and view all the answers

Centrosomes contain two tubulin-based centrioles.

<p>True (A)</p> Signup and view all the answers

What occurs during anaphase?

<p>The centromeres split and sister chromatids are pulled toward opposite poles.</p> Signup and view all the answers

During ______, the chromosomes align at the equatorial plate.

<p>metaphase</p> Signup and view all the answers

Match the following stages of cell division with their descriptions:

<p>Prophase = Nuclear membrane dissolves Metaphase = Chromosomes align at metaphase plate Anaphase = Sister chromatids separate Telophase = Nuclear membrane reformation occurs</p> Signup and view all the answers

What is the role of kinetochores in mitosis?

<p>To provide attachment points for kinetochore fibers (A)</p> Signup and view all the answers

Cytokinesis occurs before telophase.

<p>False (B)</p> Signup and view all the answers

How many divisions can human somatic cells typically undergo?

<p>20 to 50</p> Signup and view all the answers

The ______ disappears during telophase.

<p>spindle apparatus</p> Signup and view all the answers

What marks the end of telophase?

<p>Separation of the cytoplasm (D)</p> Signup and view all the answers

Flashcards

Diploid Cell

A type of cell that contains two copies of each chromosome, one copy from each parent.

Haploid Cell

A type of cell that contains one copy of each chromosome.

Cell Cycle

The process by which a cell replicates its genetic material and divides into two identical daughter cells.

G1 Phase

The phase of the cell cycle where the cell prepares for DNA replication.

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S Phase

The phase of the cell cycle where the cell replicates its DNA.

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G2 Phase

The phase of the cell cycle where the cell prepares for mitosis, ensuring everything is ready for division.

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M Phase

The phase of the cell cycle where the cell divides into two daughter cells.

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G0 Phase

A state where cells are metabolically active but not preparing to divide.

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Chromatin

The form of DNA in the nucleus during interphase, allowing for access and transcription of genetic information.

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Chromosomes

The condensed form of DNA that forms during mitosis, facilitating proper distribution to daughter cells.

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Restriction Point

A crucial checkpoint in the G1 phase, ensuring the cell meets certain criteria before entering the S phase.

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DNA Replication

The process of replicating the genetic material during the S phase, resulting in two identical sister chromatids for each chromosome.

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G2 Checkpoint

A checkpoint in the G2 phase that ensures the cell has enough organelles and that DNA replication was accurate.

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Mitosis

The process of nuclear division, consisting of four phases: prophase, metaphase, anaphase, and telophase.

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Cytokinesis

The division of the cytoplasm, completing cell division after mitosis.

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Checkpoint

A critical point in the cell cycle, particularly at the G1/S and G2/M transitions, where the cell checks for errors and damage.

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p53 Protein

A protein that plays a vital role in recognizing DNA damage and activating checkpoint mechanisms.

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Cyclins

Proteins that control the progression of the cell cycle by forming complexes with cyclin-dependent kinases, activating transcription factors.

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Cyclin-Dependent Kinases (CDKs)

Enzymes that depend on cyclins for activity and help regulate the cell cycle.

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Cancer

The uncontrolled division of cells, often caused by mutations in vital genes like TP53.

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Metastasis

The spreading of cancer cells to distant locations through the bloodstream or lymphatic system.

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Prophase

The first phase of mitosis, where the chromatin condenses, the nuclear membrane dissolves, and centrioles start to form spindle fibers.

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Metaphase

The second phase of mitosis, where chromosomes line up at the center of the cell, attached to spindle fibers.

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Anaphase

The third phase of mitosis, where sister chromatids are separated and pulled toward opposite poles of the cell.

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Telophase

The fourth phase of mitosis, where the nuclear membrane reforms around chromosomes, chromosomes uncoil, and nucleoli reappear.

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Apoptosis

The programmed death of cells, limiting the number of times a cell can divide.

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Hayflick Limit

The number of times a human cell can divide before undergoing apoptosis.

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Cellular Differentiation

The ability for cells to differentiate into specific cell types during development.

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Meiosis

A type of cell division found in germ cells, leading to gametes (sperm or egg).

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Cytokinesis (in plants)

The process by which a cell converts its cytoplasm into a new cell wall, often forming new cells in plants.

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Study Notes

Cell Composition and Phases

  • Autosomal cells are diploid (2n), containing two copies of each chromosome, while germ cells are haploid (n) with one copy.
  • In humans, autosomal (46 chromosomes) and germ cells (23 chromosomes) reflect inheritance from both parents.
  • Eukaryotic cells undergo replication in a defined cell cycle, leading to cell growth, DNA synthesis, and division.

The Cell Cycle Overview

  • The cell cycle has four phases: G1 (presynthetic gap), S (synthesis), G2 (postsynthetic gap), and M (mitosis).
  • Interphase (G1, S, G2) comprises 90% of the cell cycle duration; actively dividing cells spend most time here.
  • Cells in the G0 phase are metabolically active but not preparing to divide.

Interphase Details

  • Chromosomes are in chromatin form during interphase, allowing access for transcription.
  • Mitosis requires the DNA to condense into chromosomes for distribution during division.

G1 Stage: Presynthetic Gap

  • Organelles for energy (mitochondria) and protein production (ribosomes, endoplasmic reticulum) are synthesized.
  • A restriction point ensures criteria, like DNA integrity, are met before transitioning to S phase.

S Stage: Synthesis of DNA

  • Genetic material replication occurs, resulting in two identical sister chromatids per chromosome.
  • The cell remains diploid (46 chromosomes) despite duplication of chromatids (92).

G2 Stage: Postsynthetic Gap

  • Another quality control checkpoint checks for sufficient organelles and correct DNA replication.
  • Ensures preparedness for mitosis.

M Stage: Mitosis and Cytokinesis

  • Mitosis consists of four phases: prophase, metaphase, anaphase, and telophase, concluding with cytokinesis.
  • Results in two genetically identical daughter cells in autosomal cells.

Cell Cycle Control and Cancer

  • Checkpoints are critical for preventing division of damaged or inadequately sized cells; key checkpoints are G1/S and G2/M.
  • p53 protein plays a vital role in DNA damage response and checkpoint function.
  • Cyclins and cyclin-dependent kinases (CDKs) drive cell cycle progression, forming complexes to activate transcription factors.

Cancer Characteristics

  • Mutations in genes like TP53 (coding for p53) lead to uncontrolled cell division, contributing to cancer development.
  • Cancer cells may exhibit rapid division and metastasis through bloodstream or lymphatic systems.

Mitosis Phases

  • Prophase: Chromatin condenses, nuclear membrane dissolves, centrioles migrate and form spindle fibers.
  • Metaphase: Chromosomes align at the metaphase plate, attached by kinetochore fibers.
  • Anaphase: Separation of sister chromatids as they are pulled toward opposite poles.
  • Telophase: Nuclear membranes reform, chromosomes uncoil, and nucleoli reappear; followed by cytokinesis, separating cytoplasm.

Limit on Cell Divisions

  • Human somatic cells divide roughly 20 to 50 times before undergoing programmed cell death, limiting continuous division.

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