Cell Division: Mitosis, Meiosis, and Cell Cycle Control

Comprehensive vocabulary flashcards covering the mechanisms of mitosis, the phases of meiosis, and the regulatory checkpoints of the cell cycle as described in the BIOL 190 lecture.

Chromosome

One strand of tightly coiled DNA wrapped around histone proteins; human body cells carry $46$ total.

Autosomes

The $22$ pairs of chromosomes that do not carry genes determining sex.

Sex-determining Chromosomes

The single pair of chromosomes ($XX$ or $XY$) that determine the sex of an individual.

Karyotype

A map or visual representation of an individual's chromosomes.

Diploid

A cell containing two copies of each chromosome type ($2n$); in humans, this is $46$ total chromosomes.

Haploid

A cell containing only one copy of each chromosome type ($n$); in humans, this is $23$ total chromosomes (e.g., sperm and egg).

Chromatin

DNA combined with proteins, typically found in a loose, non-condensed form.

Sister Chromatids

Two replicated chromosomes that are held together at a region known as the centromere.

Centromere

The specific region where sister chromatids are held together.

Centrosome

The microtubule organizing center of the cell, containing centrioles.

Spindle fibers

Condensed microtubules (fibrous protein) that organize and move chromosomes during mitosis.

$S$ Stage

The part of interphase where DNA replication occurs.

Mitosis

Nuclear division producing an exact copy of the nucleus; used for cell growth and tissue repair in body cells.

Cytokinesis

The separation of the cell into daughter cells through organelle and cytoplasmic division.

Prophase

The phase where chromosomes condense, the nuclear envelope breaks down, and centrosomes move to opposite poles.

Metaphase

The phase where spindle fibers align chromosomes vertically along the equator or metaphase plate.

Anaphase

The phase where spindle fibers pull sister chromatids apart at the centromeres toward opposite poles.

Telophase

The phase where chromosomes arrive at poles, spindle fibers disappear, and nuclear envelopes reassemble.

Cleavage furrow

A row of fibrous proteins that pinch the cells apart during telophase/cytokinesis.

$G_1$ checkpoint

An internal checkpoint where DNA is checked for damage or mutations before replication.

$G_2$ checkpoint

An internal checkpoint ensuring protein supply and cell size are adequate, and replicated DNA is checked for damage.

$M$ (metaphase)-checkpoint

A checkpoint that verifies chromosomes are correctly aligned and attached to spindles before anaphase.

Positive regulators

Molecules such as Cyclins and CDKs that promote the cell's progression to the next stage of the cycle.

Negative regulators

Tumor suppressor proteins like $p53$, $p21$, and retinoblastoma protein (Rb) that halt the cell cycle.

Apoptosis

Programmed cellular death signaled by regulatory molecules if the DNA is found to be faulty.

Telomeres

Repetitious nucleotides that cap the ends of chromosomes to protect DNA during replication; they shorten by approximately $50 \times 150$ bp each division.

Telomerase

A protein that maintains and repairs telomeres; it is typically not produced in most somatic cells.

Neoplasm

A cluster of cells with abnormal growth patterns, commonly known as a tumor.

CD95

A protein on the cell surface that activates apoptosis when the matching ligand $CD95L$ binds to it.

Meiosis

A two-stage cell division process that produces four genetically diverse haploid gametes.

Crossing-over

The random swapping of genetic material between homologous chromosomes during Prophase I.

Synapsis

The process during Prophase I where replicated homologous chromosomes pair up.

Homologous chromosomes

Chromosome pairs (one from each parent) that are similar in length and gene position.