Cell Cycle and Regulation Flashcards

Flashcards on Cell Cycle and Regulation of Cell Cycle

Cell Division

Process in which parental cell divides into 2 daughter cells; part of the cell cycle.

Purpose of Cell Division

Organism growth and repair, development of an organism, regeneration of damaged/old cells, and reproduction of an organism.

Gap Zero Phase (G0)

Cells not actively in the cell cycle; functionally active, but growth and division stop.

Mitogen

Substance that induces the cell cycle.

Cell Cycle

Sequence of events to coordinate the duplication of cellular contents and division of actively replicating cells.

Gap 1 / Growth Phase (G1)

Primary growth phase of interphase; confirms environment is favorable for proliferation before committing to DNA replication.

Restriction point

Commitment point near the end of G1; once the cell has passed this point, the cell cycle will continue even if external signals are removed.

Synthesis Phase (S)

Second phase of interphase where DNA replication occurs.

Cohesin

Associates with replicated DNA to ensure sister chromosomes stay together.

Gap 2 Phase (G2)

Last phase of interphase; cell now contains double the amount of DNA.

Centromere

DNA sequence that kinetochore attaches to.

Mitosis

Generation of 2 daughter cells (somatic) that are genetically identical to the parental cell; each daughter cell is 2n (diploid).

Meiosis

Generation of 4 daughter cells (gametes); cells are not genetically identical; each daughter cell is 1n (haploid).

M-phase (M)

Mitosis and Cytokinesis.

Prophase

Chromatin condenses into mitotic chromosome, mitotic spindle assembles, endomembrane system fragments.

Condensins

Promote chromatin compaction for easier segregation of chromosomes.

Prometaphase

Nuclear envelope breaks down during this phase, mitotic spindle attaches microtubules to kinetochores on each chromosome.

Kinetochore

Protein structure assembled at the centromere to which mitotic spindle microtubules will attach.

Metaphase

Chromosomes align at the metaphase plate.

Anaphase

Cohesin linkages between sister chromatids are broken by separase; chromosomes move to opposite poles.

Separase

Breaks down cohesion, which separates sister chromatids.

Cohesin

Holds sister chromatids together.

Securin

Prevents separase from breaking down cohesin.

APC

Breaks down securing when the time is right

Telophase

Chromosomes cluster at each centrosome, nuclear envelope re-assembles around chromosomes, mitotic chromosomes reorganized and de-condense.

Cytokinesis

Microfilaments (actin) form contractile ring; actin-myosin II contraction creates a furrow allowing 2 daughter cells to split.

Cell Cycle Control System

Guarantees events of the cell cycle occur in a set sequence, each process completed before the next one begins.

Cell Cycle Checkpoints

Is environment favorable for proliferation? Is the DNA fully replicated? Are the microtubules attached to the kinetochores of all the chromosomes?

Cyclin-dependent kinases (CDKs)

Require binding to specific cyclin to initiate kinase activity.

Cyclins

Proteins which levels rise and fall throughout the cell cycle.

Cyclin binds to a CDK

Cause the T-loop to move away from the ATP-binding cleft, allowing the CDK to bind to ATP and become active

Wee1

Phosphorylates inhibitory site = inactivation of Cdk

Cdc25

De-phosphorylates inhibitory site = activation of Cdk

Overview of Cell Cycle Control Phase 1

G1-Cdk stimulates expression of G1/S (cyclin E) and S (cyclin A) cyclins

Overview of Cell Cycle Control Phase 2

G1/S-Cdk (cyline E/cdk2)drives progression through restriction point, further induces S-Cdk activity

Overview of Cell Cycle Control Phase 3

S-Cdk (cyclin A/cdk2) stimulates DNA replication and some early M events

Overview of Cell Cycle Control Phase 4

APC induces destruction of securin and any remaining cyclins to trigger M-to-A transition and completion of mitosis

Overview of Cell Cycle Control Phase 5

APC and others suppress all CDK activity to ensure cycle completion before beginning a new cycle