Chapter 9: The Cell Cycle and Cellular Reproduction

Vocabulary practice flashcards covering the cell cycle, phases of mitosis, chromosome architecture, checkpoints, apoptosis, cytokinesis, and prokaryotic binary fission.

Binary Fission

The asexual reproduction process in prokaryotes (bacteria and archaea) where a single circular chromosome replicates and the cell divides into two identical daughter cells.

Nucleosome

A fundamental unit of DNA packaging consisting of DNA coiled around a core of eight positively charged histone proteins, resembling beads on a string with an approximate diameter of $11\text{ nm}$.

Chromatin

A diffuse complex of approximately $40\%$ DNA and $60\%$ histone proteins that condenses and folds into radial loops during the cell cycle.

Diploid ($2n$)

A condition in which a cell contains two complete sets of chromosomes of each type ($2n = 46$ in humans), with one set inherited from each parent.

Haploid ($n$)

A condition where a cell contains only a single set of chromosomes ($n = 23$ in humans), typical of mature sex cells (gametes) such as sperm and eggs.

Karyotype

An organized display or visual array of an individual organism's complete set of chromosomes, arranged according to size, staining properties, and centromere location.

Sister Chromatids

Two identical copies of a single replicated chromosome that remain linked at the centromere by cohesin proteins prior to their separation during cell division.

Centromere

The constricted region of a chromosome that holds replicated sister chromatids together and serves as the assembly platform for kinetochores.

Kinetochore

A specialized protein complex located on each sister chromatid at the centromere that provides an attachment point for spindle microtubules.

Homologous Chromosomes

Pairs of chromosomes (one maternal and one paternal) that share the same length, centromere location, and locus order for specific genes, though they may carry different versions (alleles) of those genes.

$G_1$ Stage

The first growth phase of interphase during which the cell recovers from the previous division, doubles its organelles, grows in size, and accumulates materials needed for DNA replication.

S Stage

The synthesis phase of interphase in which DNA is replicated and associated proteins are synthesized, transitioning chromosomes from one chromatid to two identical sister chromatids.

$G_2$ Stage

The interphase stage between DNA replication and the onset of mitosis, where proteins necessary for division (such as tubulin for microtubules) are synthesized and chromosomes coil more tightly.

Cyclins

A family of internal regulatory proteins whose concentrations fluctuate throughout the cell cycle, functioning to trigger progression past specific checkpoints.

Cell Cycle Checkpoints

Specific regulatory hold points ($G_1$, $G_2$, and M) where the cell cycle is monitored for accuracy, DNA integrity, and environmental readiness before allowing progression.

$p53$ Gene

A critical tumor suppressor gene located on chromosome 17 that produces a signaling protein to arrest the cell cycle at $G_1$ for DNA repair or initiate apoptosis if damage cannot be resolved.

Apoptosis

Programmed cell death mediated by caspases, characterized by nuclear fragmentation, plasma membrane blebbing, and phagocytosis by white blood cells.

Caspases

Enzymes that disassemble cellular proteins and structures to carry out programmed cell death in response to internal or external death signals.

Prophase

The first stage of mitosis during which chromatin condenses into distinct chromosomes, the nucleolus disappears, and centrosomes move apart as the mitotic spindle begins to assemble.

Prometaphase

The mitotic phase marked by the disassembly of the nuclear envelope, development of kinetochores at centromeres, and the attachment of kinetochore spindle fibers from opposite poles.

Metaphase

The mitotic stage where chromosomes are aligned across the equatorial plane (metaphase plate) under tension from opposing kinetochore microtubules.

Anaphase

The mitotic stage during which cohesin proteins holding sister chromatids are degraded, allowing individual daughter chromosomes to be pulled toward opposite spindle poles.

Telophase

The final stage of mitosis during which daughter chromosomes decondense into indistinct chromatin, nuclear envelopes re-form, nucleoli reappear, and the spindle apparatus disassembles.

Cleavage Furrow

A shallow groove that develops during animal cytokinesis via a contractile ring of actin filaments, constricting to pinch the parent cell into two daughter cells.

Cell Plate

A nascent structure formed during plant cell cytokinesis by the fusion of Golgi-derived membrane vesicles across the division plane, developing into the plasma membranes and middle lamella.

Reproductive Cloning

A biotechnology procedure that produces a genetically identical live individual by fusing a donor cell nucleus with an enucleated egg and implanting the resulting embryo into a surrogate mother.

Therapeutic Cloning

The cultivation of embryonic or adult stem cells in tissue culture to generate specialized human cell types or tissues for medical treatment and cellular repair.

Nucleoid

The non-membrane-bound cytoplasmic region in a prokaryotic cell where the single, circular chromosome of DNA is located.

Septum

The new partition of cell wall and plasma membrane that forms and grows inward to divide a bacterial cell into two separate daughter cells during binary fission.