Continuity and change: Cells and nuclear division

VOCABULARY flashcards covering key terms from the notes on cell division, meiosis, and the cell cycle.

Mitosis

Nuclear division that preserves chromosome number, producing two diploid, genetically identical daughter nuclei.

Meiosis

Nuclear division that halves chromosome number to produce haploid gametes and increases genetic diversity via crossing over and independent assortment.

Cytokinesis

Division of the cytoplasm after mitosis/meiosis; in animals an actin ring forms a cleavage furrow; in plants vesicles fuse to form a cell plate.

Diploid (2n)

Having two complete sets of chromosomes; in humans somatic cells are diploid (46 total).

Haploid (n)

Having a single set of chromosomes; gametes are haploid (23 in humans).

Sister chromatids

Two identical copies of a replicated chromosome held together at the centromere until separation.

Centromere

Constricted region of a chromosome where sister chromatids stay attached and where spindle fibers attach during division.

Zygote

The diploid cell formed when a sperm fertilizes an egg; the first cell of the developing organism.

Polar bodies

Small haploid cells produced during oogenesis (First and Second polar bodies) that are typically degraded; the egg retains most cytoplasm.

Crossing over

Exchange of genetic material between non-sister chromatids during meiosis I, creating genetic diversity.

Nondisjunction

Failure of chromosome pairs or chromatids to separate during meiosis or mitosis, leading to abnormal chromosome numbers (e.g., trisomy, Down syndrome); risk increases with maternal age.

Interphase

Cell cycle phase where the cell grows, DNA is replicated (S), and checkpoints monitor progress (G1, S, G2).

Cyclins

Regulatory proteins that activate cyclin-dependent kinases (Cdks) to drive the cell cycle; different cyclins regulate G1, S, and M phases.

Oncogenes

Mutated proto-oncogenes that can promote cancer when overactive or misregulated; part of cell cycle control.

Tumor suppressor genes

Genes that normally restrain the cell cycle and prevent cancer; when inactivated, cancer risk increases.