Cell Cycle and Mitosis Lecture Notes

Vocabulary flashcards covering foundational terms for understanding the cell cycle, mitosis, and meiosis.

Cell Division

The process by which a parent cell splits into two or more daughter cells.

Cell Cycle

The ordered series of events that lead to cell growth, DNA duplication, and cell division.

Mitosis

Vegetative nuclear division that produces two genetically identical diploid daughter cells.

Meiosis

Reproductive division that halves chromosome number to create genetically unique haploid gametes.

Interphase

Phase of the cell cycle (G1, S, G2) in which the cell grows and replicates DNA, occupying ~95 % of the cycle.

G1 Phase (Gap 1)

First stage of interphase where the cell grows and is metabolically active without replicating DNA.

S Phase (Synthesis)

Interphase stage in which DNA replication converts 2 N DNA content to 4 N without changing chromosome number.

G2 Phase (Gap 2)

Interphase stage where the cell synthesizes RNA, proteins, and organelles in preparation for mitosis.

G0 Phase

Quiescent state where non-dividing cells remain metabolically active but exit the cell cycle unless reactivated.

Checkpoint

Control mechanism that verifies whether critical processes are completed correctly before cell-cycle progression.

G1 Checkpoint (Restriction Point)

Control point that assesses nutrients, size, DNA damage, and external signals before committing to DNA synthesis.

G2 Checkpoint

Pre-mitotic control point ensuring DNA has been fully and accurately replicated.

M Checkpoint (Spindle Assembly)

Metaphase control point that confirms all chromosomes are properly attached to spindle fibers before anaphase.

Chromatin

Less-condensed DNA–protein complex found in the nucleus during interphase.

Chromosome

Highly condensed DNA structure visible during cell division, consisting of two sister chromatids joined at a centromere.

Chromatid

One of two identical DNA strands of a replicated chromosome.

Sister Chromatids

Pair of identical chromatids joined at the centromere after DNA replication.

Homologous Chromosomes

Matched pair of chromosomes—one maternal, one paternal—with the same genes in the same order.

Centromere

Region where sister chromatids are attached and where spindle fibers connect via kinetochores.

Spindle Fibers

Microtubules that attach to kinetochores and separate chromosomes during division.

Metaphase Plate

Imaginary plane equidistant from cell poles where chromosomes align during metaphase.

Cytokinesis

Division of the cytoplasm that follows nuclear division, producing two separate cells.

Diploid (2n)

Cell containing two complete sets of chromosomes; typical of somatic cells.

Haploid (n)

Cell containing one complete set of chromosomes; characteristic of gametes.

Somatic Cell

Any body cell except reproductive (gamete) cells; divides by mitosis.

Gamete

Sex cell (sperm or egg) produced by meiosis; haploid in chromosome number.

Prophase

First mitotic stage where chromosomes condense, nuclear membrane dissolves, and spindle forms.

Metaphase

Mitotic stage where chromosomes align at the metaphase plate attached to spindle fibers.

Anaphase

Mitotic stage where sister chromatids separate and move to opposite poles.

Telophase

Mitotic stage where chromosomes reach poles, decondense, and nuclear envelopes reform.

Tetrad

Structure of paired homologous chromosomes (four chromatids) formed during prophase I of meiosis.

Synapsis

Process of homologous chromosome pairing during meiosis I.

Crossing Over

Exchange of genetic material between homologous chromatids, generating variation.

Independent Assortment

Random orientation of homologous pairs in metaphase I, producing varied gamete combinations.

Spindle Apparatus

Entire microtubule structure—including centrosomes and fibers—that orchestrates chromosome movement.

Genetic Variation

Differences in DNA sequences among individuals produced by crossing over and independent assortment during meiosis.