The Cell Cycle – Botany Lecture No. 4

Vocabulary flashcards covering key terms and definitions related to plant cell cycle, mitosis, and cytokinesis as presented in Lecture No. 4.

Cell Cycle

Ordered sequence of events in a cell’s life, consisting of interphase (G1, S, G2) followed by the M phase (mitosis + cytokinesis).

Interphase

Preparatory portion of the cell cycle (G1, S, G2) during which the cell grows, replicates DNA, and readies structures for division.

G0 Phase

Non-dividing, quiescent state a cell may enter from G1 when it exits the active cycle.

G1 Phase

First gap of interphase; cell size, organelles, enzymes, and molecules increase rapidly.

S Phase

Synthesis phase of interphase in which DNA and associated proteins are replicated, producing two copies of the genome.

G2 Phase

Second gap of interphase; division machinery assembles, chromosomes start to condense, and DNA damage is checked.

M Phase

Mitotic phase comprising mitosis (nuclear division) and cytokinesis (cytoplasmic division).

G1 Checkpoint

Control point at the end of G1 that decides if the cell proceeds to DNA synthesis.

G2 Checkpoint

Control point at the end of G2 ensuring DNA replication is complete and undamaged before mitosis begins.

Mitosis

Type of nuclear division producing two genetically identical daughter nuclei in four stages: prophase, metaphase, anaphase, telophase.

Cytokinesis

Division of the cytoplasm; in plant cells it involves formation of a cell plate that separates daughter cells.

Prophase

First mitotic stage; chromatin condenses into visible chromosomes, nucleolus and nuclear envelope disintegrate, and spindle starts to form.

Metaphase

Second mitotic stage; spindle microtubules attach to kinetochores and chromosomes align on the metaphase plate.

Anaphase

Shortest mitotic stage; sister chromatids separate simultaneously and migrate to opposite spindle poles as daughter chromosomes.

Telophase

Final mitotic stage; nuclear envelopes re-form, chromosomes decondense, nucleoli reappear, and the cell plate begins to develop.

Sister Chromatids

Identical copies of a chromosome held together at the centromere after DNA replication.

Centromere

Constricted chromosome region where sister chromatids are joined and where kinetochores form.

Kinetochore

Protein complex on each chromatid’s centromere that attaches to spindle microtubules.

Mitotic Spindle

Microtubule framework that organizes and separates chromosomes during mitosis.

Kinetochore Microtubules

Spindle fibers that connect kinetochores to spindle poles, pulling chromosomes during segregation.

Polar Microtubules

Spindle fibers that overlap at the cell equator and push poles apart, helping elongate the cell.

Phragmoplast

Plant-specific microtubule array forming between daughter nuclei during telophase to guide cell-plate assembly.

Cell Plate

Flattened structure arising from fused Golgi (dictyosome) vesicles in the phragmoplast; matures into new primary walls and plasma membranes.

Phragmosome

Cytoplasmic sheet formed by strands traversing a large vacuole, positioning the nucleus centrally before division in large plant cells.

Preprophase Band

Ring of microtubules encircling the nucleus just before prophase, marking the future plane of cell division.