🧬 LAB 9 – MITOSIS QUIZLET SET

Mitosis

Division of the nucleus resulting in two genetically identical daughter cells.

Purpose of mitosis

Growth, repair, and maintenance of multicellular organisms.

Cell cycle

The sequence of events a cell goes through during growth and division.

Main stages of cell cycle

Interphase and Mitotic (M) phase.

Interphase

Period of cell growth and DNA replication before mitosis.

Phases of interphase

G₁, S, and G₂.

G₁ phase

Cell grows, performs normal functions, and prepares for DNA synthesis.

S phase

DNA replication occurs.

G₂ phase

Cell prepares for mitosis; organelles and proteins synthesized.

M phase

Includes mitosis and cytokinesis.

Cytokinesis

Division of cytoplasm into two separate daughter cells.

Mitosis stages

Prophase, Metaphase, Anaphase, Telophase.

Interphase characteristics

Nucleus visible; chromatin uncoiled; DNA replication completed.

Prophase

Chromatin condenses into visible chromosomes; spindle fibers form; nuclear envelope dissolves.

Late prophase (prometaphase)

Spindle attaches to kinetochores; chromosomes start moving.

Metaphase

Chromosomes align along metaphase plate (cell equator).

Metaphase plate

Imaginary line where chromosomes line up in middle of cell.

Anaphase

Sister chromatids separate and move toward opposite poles.

Telophase

Nuclear envelopes reform; chromosomes uncoil into chromatin.

Cytokinesis in animal cells

Cytoplasm divides by cleavage furrow formation.

Cytokinesis in plant cells

Cell plate forms in middle, later becoming new cell wall.

Cleavage furrow

Indentation in animal cell membrane during cytokinesis.

Cell plate

New structure that forms in plant cells during cytokinesis.

Spindle fibers

Microtubules that pull sister chromatids apart during mitosis.

Centrosome

Organelle that organizes spindle microtubules.

Centriole

Structure found in animal centrosomes that aids spindle formation.

Aster

Star-shaped array of microtubules radiating from centrosome.

Chromatin

Uncoiled form of DNA in interphase.

Chromosome

Condensed DNA molecule with associated proteins.

Chromatid

One half of a duplicated chromosome.

Sister chromatids

Identical copies of a chromosome joined by a centromere.

Centromere

Region joining sister chromatids; attachment site for spindle fibers.

Kinetochore

Protein complex on centromere where spindle fibers attach.

Purpose of spindle apparatus

Ensure equal chromosome distribution to daughter cells.

Diploid cell

Cell with two sets of chromosomes (2n).

Result of mitosis

Two identical diploid daughter cells.

Mitosis in onion root tip

Rapid cell division; used to observe mitotic stages.

Most common stage in onion root tip

Interphase (cells spend most of time here).

Mitosis under microscope

Stained cells show chromosomes in distinct phases.

Animal mitosis example

Whitefish blastula.

Plant mitosis example

Onion root tip.

Difference between plant and animal mitosis

Plant cells form cell plate; animal cells form cleavage furrow.

Significance of mitosis

Maintains chromosome number; ensures genetic stability.

Errors in mitosis

Can lead to aneuploidy or cancer.

G₀ phase

Resting phase where cells do not divide (e.g., neurons).

Checkpoint in G₁

Determines whether cell proceeds to division or enters G₀.

Checkpoint in G₂

Ensures DNA is replicated and undamaged before mitosis.

M checkpoint

Ensures spindle fibers attached correctly to chromosomes.

Role of cyclins

Regulate progression of cell cycle.

Role of cyclin-dependent kinases (CDKs)

Activate or deactivate proteins for cell cycle transitions.

Prophase model identification

Chromosomes condensing, nucleus fading, spindle forming.

Metaphase model identification

Chromosomes aligned at equator.

Anaphase model identification

Sister chromatids moving toward poles.

Telophase model identification

Two nuclei forming, chromosomes decondensing.

Interphase model identification

Intact nucleus with uncoiled chromatin.

Mitosis model order

Interphase → Prophase → Metaphase → Anaphase → Telophase → Cytokinesis.

Chromosomes appear first

Prophase.

Chromosomes align

Metaphase.

Chromosomes separate

Anaphase.

Chromosomes decondense

Telophase.

Nuclear envelope reappears

Telophase.

Spindle fibers disappear

Telophase.

Two daughter nuclei visible

Late telophase.

Mitosis function summary

Produces two identical cells for tissue growth and repair.

End of mitosis vs end of cytokinesis

End of mitosis = two nuclei; end of cytokinesis = two separate cells.

Observation tip for lab exam

Identify nucleus, chromosomes, and spindle orientation to determine stage.

Mitotic index

Percentage of cells undergoing mitosis in a population.

High mitotic index tissue

Indicates active growth (e.g., root tip).

Low mitotic index tissue

Indicates slow or no cell division.

Lab purpose for mitosis

Identify and describe stages using models and microscope slides.