Mitosis General Biology M5

Vocabulary flashcards covering key terms and concepts from the lecture notes on mitosis.

G1 Phase

The first subphase of interphase where the cell grows and synthesizes mRNA and proteins needed for DNA replication; centrosomes and chromosomes appear; energy and nutrients are processed; contains G1 DNA-damage checkpoint and Restriction Checkpoint.

G1 DNA-damage checkpoint

Evaluates the DNA’s integrity; if damaged beyond repair, p53 accumulates and the cell cycle is halted or directed to apoptosis.

p53 (TP53)

Tumor suppressor protein that monitors DNA; accumulates to halt the cell cycle or induce apoptosis when damage is severe.

Restriction Checkpoint

Assesses the cell’s readiness to divide; if ready, proceeds to S phase; otherwise enters G0.

G0

Quiescent (dormant) or Senescent (aging) state; occurs when conditions cannot sustain division; quiescent cells can return to division with proper stimulus.

S Phase

DNA synthesis phase where chromosomes are replicated; each chromosome duplicates to form two identical sister chromatids; DNA content doubles; S DNA-damage checkpoint monitors replication.

S DNA-damage checkpoint

Monitors replication integrity during S phase to ensure accuracy.

G2 Phase

Second growth phase where the cell rapidly grows, continues protein synthesis, and the mitotic spindle begins to form.

G2 DNA-damage checkpoint

Checks activities in G2 to ensure DNA integrity before entering mitosis.

Unreplicated DNA checkpoint

Ensures DNA synthesis is complete before proceeding to mitosis.

Prophase

Chromosomes condense and become visible; each chromosome consists of two sister chromatids held at a single centromere; parts include centromere, kinetochore, and spindle fibers.

Centromere

Region of the chromosome to which the spindle fiber attaches during cell division.

Kinetochore

Protein complex at the centromere that links spindle fibers to chromosomes.

Spindle fibers

Microtubules that attach to kinetochores and shorten/lengthen to separate chromatids; originate from centrosomes.

Prometaphase

Nucleolus and nuclear envelope disappear; spindle apparatus attaches to chromosomes.

Metaphase

Chromosomes align at the metaphase plate; three kinds of microtubules (astral, polar, kinetochore) organize spindle and ensure proper alignment.

Astral microtubules

Grow near the centrosome and help position the spindle.

Polar microtubules

Grow away from the centrosome and help push poles apart.

Kinetochore microtubules

Attach to kinetochores and pull chromosomes toward the metaphase plate.

Metaphase plate

The plane where chromosomes align during metaphase at the center of the cell.

Anaphase

Two substages Anaphase A and Anaphase B; chromatids separate and move toward poles while poles separate.

Anaphase A

Kinetochore microtubules shorten, pulling sister chromatids toward opposite poles.

Anaphase B

Polar microtubules lengthen and push poles apart; astral microtubules assist by pulling on the cell cortex.

Telophase

Chromosomes arrive at poles, de-condense; nucleolus and nuclear envelope reappear; chromosome segregation checkpoint ensures proper separation before cytokinesis.

Cytokinesis

Division of the cytoplasm; begins in anaphase and completes two daughter cells; cleavage furrow forms in animals, cell plate forms in plants.

Cleavage furrow

Contractile ring constricts the middle of the animal cell membrane to produce two daughter cells.

Cell plate

Vesicle-derived structure that forms the separating cell wall between plant daughter cells during cytokinesis.

Diploid

A cell that contains two complete sets of chromosomes; in the notes, mitosis produces diploid cells containing 6 chromosomes each.

Chromosome

DNA-protein complex carrying genetic information; becomes visible as condensed structures during mitosis.

Sister chromatids

Two identical copies of a chromosome created during DNA replication and held together at the centromere.

Cancer and p53

Mutation of p53 can disable DNA damage checkpoints, permitting uncontrolled cell division and cancer.