Cell Division and the Cell Cycle

Vocabulary practice flashcards covering bacterial cell division, chromosome organization, cell cycle phases, mitosis, and cytokinesis.

Origin of replication

The specific site on double-stranded circular bacterial DNA where replication begins prior to cell division.

FtsZ

A bacterial protein molecule that assembles into a ring at approximately the cell midpoint to facilitate septation and binary fission.

Septation

The process in bacterial cell division where new membrane and cell wall material grow inward at approximately the midpoint of the cell to form a dividing septum.

Chromatin

The structural complex of eukaryotic chromosomes composed of approximately $40\%$ DNA and $60\%$ protein.

Karyotype

The particular array of chromosomes in an individual organism, arranged according to characteristics such as size, staining properties, and the position of the centromere.

Diploid ($2n$)

Possessing two complete sets of chromosomes, equal to a total of $46$ chromosomes in humans.

Haploid ($n$)

Possessing one set of chromosomes, which corresponds to $23$ chromosomes in humans.

Centromere

The point of constriction along a eukaryotic chromosome where sister chromatids are joined.

Kinetochore

A protein structure located at the centromere of each sister chromatid that functions as the attachment site for spindle microtubules.

Cohesin

A protein complex that holds sister chromatids together at the centromere following DNA replication.

$G_1$ phase

The primary growth phase and typically the longest, most variable phase of the eukaryotic cell cycle.

$S$ phase

The synthesis phase of interphase during which the cell replicates its genomic DNA.

$G_2$ phase

The second gap phase of interphase during which organelles replicate, tubulin is synthesized, motor proteins coil chromosomes more tightly, and centrioles replicate.

$G_0$ phase

A resting phase of the cell cycle where cells pause and spend variable amounts of time outside of active cell division.

Asters

A radial array of microtubules formed around centrioles in animal cells during prophase, which does not form in plant cells.

Metaphase plate

The equatorial plane along which duplicated chromosomes align during metaphase, defining the future axis of cell division rather than an actual physical structure.

Anaphase A

The phase of chromosome movement during anaphase in which kinetochores and chromatids are pulled toward opposite spindle poles.

Anaphase B

The phase of chromosome segregation during anaphase in which the spindle poles themselves move farther apart.

Cleavage furrow

The pinching groove formed in animal cells during cytokinesis as a contractile ring of actin filaments constricts.

Cell plate

The partition that forms between divided nuclei in plant cells during cytokinesis through the fusion of membrane-carrying vesicles.