Cell Division

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Questions and Answers

Which process does NOT occur during interphase?

  • Preparation for mitosis
  • DNA replication
  • Chromosome segregation (correct)
  • Cell growth

Pancreatic cancer is always directly caused by mutations in the Ras protein.

False (B)

What is the name for the series of stages that a cell goes through to grow and divide?

cell cycle

The four main stages of the eukaryotic cell cycle are G1, S, G2, and ______.

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

Match the following cell cycle phases with their primary event:

<p>G1 phase = Cell growth and decision-making S phase = DNA replication G2 phase = Preparation for mitosis M phase = Nuclear and cytoplasmic division</p> Signup and view all the answers

What is the role of mitogens in the cell cycle?

<p>To stimulate a cell to begin mitosis (A)</p> Signup and view all the answers

DNA replication occurs during the G1 phase of the cell cycle.

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

What is the period between two M phases called?

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

The enzyme that duplicates the DNA during S phase is called DNA ______.

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

Match the following phases of mitosis with their key events:

<p>Prophase = Chromosomes condense Metaphase = Chromosomes align at the equator Anaphase = Sister chromatids separate Telophase = Nuclear envelope reassembles</p> Signup and view all the answers

What triggers the separation of sister chromatids during anaphase?

<p>Ubiquitylation and degradation of securin (C)</p> Signup and view all the answers

The mitotic spindle is made of actin and myosin filaments.

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

What structures mediate M phase?

<p>cytoskeletal structures</p> Signup and view all the answers

The contractile ring that divides the cytoplasm during cytokinesis is made of actin and ______ filaments.

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

Match the following cell cycle checkpoints with their functions:

<p>G1 checkpoint = Checks for favorable environment and DNA damage G2 checkpoint = Checks for complete DNA replication and DNA damage M checkpoint = Checks for proper chromosome attachment to the spindle</p> Signup and view all the answers

What is the main function of the cell-cycle control system?

<p>To regulate the sequence of events in the cell cycle (D)</p> Signup and view all the answers

Cdks (cyclin-dependent kinases) are always active, regardless of cyclin binding.

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

What molecule is phosphorylated by G1/S-Cdk to promote entry into S phase?

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

The activity of Cdks can be blocked by binding to a Cdk ______.

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

Match the following Cyclin-Cdk complexes with their roles:

<p>G1-Cdk = Regulates cell growth and preparation for DNA replication S-Cdk = Initiates DNA replication M-Cdk = Promotes entry into mitosis</p> Signup and view all the answers

What is the function of S-Cdk in DNA replication?

<p>Initiating DNA replication and preventing re-replication (D)</p> Signup and view all the answers

Mitosis results in four daughter cells, each with half the number of chromosomes as the parent cell.

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

In which phase of the cell cycle is the centrosome duplicated?

<p>G2</p> Signup and view all the answers

During prometaphase, chromosomes attach to the mitotic spindle via structures called ______.

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

Match each phase with a description of what happens to the chromosomes

<p>Prophase = Chromosomes condense. Prometaphase = Chromosomes attach to microtubules Metaphase = Chromosomes line up at the equator of the cell. Anaphase = Sister chromatids separate. Telophase = New nuclear envelopes form.</p> Signup and view all the answers

What might occur if DNA is damaged during the G1 phase?

<p>The cell cycle arrests, allowing time for DNA repair. (A)</p> Signup and view all the answers

Growth factors always directly cause cells to divide, regardless of other conditions.

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

Name two transient structures that mediate M phase?

<p>mitotic spindle and contractile ring</p> Signup and view all the answers

Proper attachment of each kinetochore to a spindle fiber is checked at the ____ checkpoint.

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

Match the following descriptions with the phases of mitosis they describe

<p>Prophase = Nuclear envelope disappears. Anaphase = Sister chromatids separate. Telophase = Chromosomes decondense.</p> Signup and view all the answers

Flashcards

Cell Division

Cell division requires the duplication of the cell's contents to create two daughter cells.

Cell Cycle

The series of stages a cell goes through to grow and divide into two daughter cells.

Events of Cell Reproduction

Growth, chromosome duplication, chromosome segregation, and cell division.

Cell Cycle Stages

G1, S, G2, and M.

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G1 Phase

The cell grows, decides whether to divide, withdraws, or differentiates.

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Cell Fates in G1

Remaining in G1, withdrawing into G0, terminal differentiation, or entry into S phase.

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S Phase

DNA replication occurs, duplicating the DNA molecules.

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G2 Phase

The cell increases in size, DNA is checked and centrosome is duplicated.

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M Phase

Nuclear division (mitosis) and cytoplasmic division (cytokinesis).

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Mitosis Stages

Prophase, prometaphase, metaphase, anaphase, and telophase.

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Prophase

Duplicated chromosomes condense during this stage.

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Prometaphase

Breakdown of the nuclear envelope.

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Metaphase

Chromosomes align at the equator of the cell.

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Anaphase

Sister chromatids separate and move to opposite spindle poles.

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Telophase

A new nuclear envelope reassembles around each set of chromosomes.

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Cytokinesis

Cytoplasm is divided in two by a contractile ring of actin and myosin filaments.

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Types of Cell Division

Mitosis and Meiosis.

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Cell-Cycle Control System

A system that ensures key processes occur in the proper sequence.

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Cell Cycle Transition Points

G1 to S, G2 to M, and metaphase to anaphase.

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Cdks

Cyclin-dependent protein kinases.

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Cyclin-Cdk Complexes

Progression through the cell cycle depends on these.

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Cyclin-Cdk Complex Types

G1-Cdk, G1/S-Cdk, S-Cdk and M-Cdk.

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Cdk Activity Regulation

It happens through cyclin degradation, phosphorylation, and Cdk inhibitors.

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Mitogens

Growth factors that stimulate cell division.

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DNA Damage and Cell Cycle

The cell cycle control pauses if damage is detected.

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Cell Cycle Checkpoints

They rely on cell cycle checkpoints in G1, G2 and M.

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S-Cdk and DNA Replication

S-Cdk phosphorylates DNA helicase.

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Pancreas Function

Helps with digestion and glycemia regulation.

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Growth Factors

Factors that promote cell proliferation.

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Growth Factors and Cell Proliferation

Cell proliferation by activating the Ras/MAPK pathway.

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Study Notes

Pancreatic Cancer

  • Pancreas plays roles in both digestion and glycemia regulations
  • Pancreas can repair and regenerate itself using specific growth factors
  • Growth promotes cell proliferation by activating the Ras/MAPK pathway
  • Growth factor signaling has been linked to pancreatic cancer
  • Approximately 74% of pancreatic cancer cases involve mutations in the Ras protein

Cell Division - Content Duplication

  • A cell replicates through an organized series of events
  • The main steps include growth, chromosome duplication, chromosome segregation, and cell division
  • The cell cycle is the series of stages a cell passes through to grow and divide into two daughter cells
  • The cell cycle duration varies between different cell types

Eukaryotic Cell Cycle Stages

  • The four phases are G1, S, G2, and M
  • DNA replication occurs during the S phase
  • Nuclear division (mitosis) and cytoplasmic division (cytokinesis) happen during the M phase
  • The cell grows in G1 stage
  • The cell prepares for mitosis in G2 stage
  • Interphase is the period between two M phases

G1 Phase - Decision Making

  • During G1, a cell decides to: remain in G1, withdraw into G0, undergo terminal differentiation, or enter the S phase
  • Entry into S phase needs a mitogen, an extracellular signal
  • Mitogens trigger a cell to start mitosis
  • Certain growth factors function as mitogens

S Phase - DNA Replication

  • DNA replication duplicates present DNA molecules
  • DNA replication starts at specific points known as origins of replication

G2 Phase - Pre-Mitosis

  • The centrosome duplicates during G2

M Phase - Cell Division

  • Nuclear division and cytoplasmic division forms the stages of M phase
  • Mitosis has 5 stages: prophase, prometaphase, metaphase, anaphase, and telophase
  • M phase is mediated by the two transient cytoskeletal structures.

Prophase

  • Duplicated chromosomes condense

Prophase - Mitotic Spindle

  • The mitotic spindle forms between the two centrosomes

Prometaphase

  • Prometaphase begins with the breakdown of the nuclear envelope

Prometaphase - Chromosome Attachment

  • Chromosomes attach to spindle microtubules using kinetochores

Metaphase

  • Chromosomes align along the cell's equator, during metaphase

Anaphase

  • Sister chromatids separate and move towards opposite spindle poles during anaphase

Telophase

  • A new nuclear envelope reassembles around each set of chromosomes in telophase
  • Cytoplasm division starts

Cytokinesis

  • Cytokinesis divides the cytoplasm into two via a contractile ring of actin and myosin filaments
  • Cytoplasmic division initiates

Cell Division Types

  • Eukaryotic cells undergo mitosis and meiosis

Cell Cycle Control System

  • Eukaryotic cells possess a cell-cycle control system
  • The system makes sure steps happen in the correct order
  • The cycle can pause at transition points
  • The cycle's transition points: G1 to S phase, G2 to M phase, and metaphase to anaphase

Cdks - Cell Cycle Control

  • Progression through the cell cycle uses cyclin-dependent protein kinases (Cdks)
  • A Cdk has to bind a regulatory protein called cyclin to be active
  • Cyclin-Cdk complexes phosphorylate proteins in cell cycle progression
  • There are different cyclins and Cdks

Cyclin-Cdk Complexes

  • Cdks activity is regulated by their associated cyclins
  • Four Cyclin-Cdk complexes exist: G1-Cdk, G1/S-Cdk, S-Cdk, and M-Cdk

Cdk Regulation

  • Cyclin degradation regulates Cdks
  • Phosphorylation and dephosphorylation controls the activity of cyclin-cdk complexes
  • A Cdk inhibitor can block Cdk activity, such as p27 or p21

Cell Cycle Checkpoints

  • The cell cycle includes checkpoints
  • The cell cycle checkpoints occur in G1, G2, and M

Cell Division Triggering

  • Cell division is stimulated by mitogen, a growth factor
  • A signaling pathway targeting G1/S-Cdk is activated by mitogen signals
  • G1/S-Cdk phosphorylates Rb, which activates the transcription regulator E2F and the expression of S-phase related genes

DNA Replication Initiation

  • S-Cdk initiates DNA replication through phosphorylating DNA helicase
  • S-Cdk activity stops DNA re-replication in one S phase by phosphorylating Cdc6

DNA Damage Detection

  • If DNA damage is detected, the cell-cycle control system stops the cell cycle

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