Lesson 6 Cell Division: Mitosis and Meiosis

A set of vocabulary flashcards covering key terms and definitions related to the cell cycle, mitosis, and meiosis as presented in Lesson 6.

Cell Cycle

The ordered series of events by which a cell grows, duplicates its genetic material, and divides to form two daughter cells; a cycle rather than a linear path.

Interphase

The non-dividing phase of the cell cycle during which the cell grows and copies its DNA; includes G1, S, and G2; the longest phase.

G1 Phase (First Gap Phase)

Cell grows in volume, duplicates organelles (including centrioles), and prepares chemicals for DNA synthesis.

S Phase (Synthesis Phase)

DNA replication occurs and histones are synthesized; chromosomes replicate.

G2 Phase (Second Gap Phase)

Preparation for mitosis; further growth and beginning of mitotic spindle formation.

Mitosis

Division of the nucleus (karyokinesis) into two genetically identical nuclei; typically followed by cytokinesis.

PMAT

Acronym for the four mitotic stages: Prophase, Metaphase, Anaphase, Telophase.

Prophase

Chromatin condenses into chromosomes; centrioles duplicate; nuclear envelope breaks down; mitotic spindle forms.

Metaphase

Chromosomes align at the metaphase plate; spindle fibers attach to kinetochores at centromeres; nuclear envelope is absent.

Anaphase

Sister chromatids separate and move toward opposite poles; chromosomes segregate as spindle fibers shorten.

Telophase

Chromosomes arrive at poles; nuclear envelope reforms around each set; nucleolus reappears.

Cytokinesis

Division of the cytoplasm to form two distinct daughter cells; concludes cell division; cleavage furrow forms in animals.

Cleavage furrow

Indentation of the cell membrane that splits the cytoplasm during cytokinesis in animal cells.

Nuclear envelope

Membrane surrounding the nucleus that breaks down in prophase and reforms in telophase.

Nucleolus

Nuclear structure that re-forms during telophase and is involved in ribosome synthesis.

Chromatin

Uncondensed DNA-protein complex that condenses into chromosomes during cell division.

Chromosome

DNA molecule packaged with proteins; becomes visible as condensed structures during mitosis.

Centromere

Constricted region of a chromosome where sister chromatids are held together and kinetochores attach.

Centriole

Organelles that organize the spindle apparatus; duplicate before mitosis and migrate to poles.

Spindle fibers / Mitotic spindle

Microtubules and proteins that separate chromosomes during cell division.

Nuclear membrane / Nuclear envelope

Membrane around the nucleus; called nuclear envelope in cellular context; breaks down and reforms during mitosis.

Go phase (G0 phase)

A non-dividing state where cells are not actively preparing to divide; external signals can trigger re-entry.

G0 Phase

Alternative term for the non-dividing resting phase of some cells.

Meiosis

Type of cell division reducing the chromosome number by half through two successive divisions.

Meiosis I

Reduction division; homologous chromosomes pair and separate, producing two haploid cells with duplicated chromosomes.

Meiosis II

Equational division; sister chromatids separate, producing four haploid gametes.

Prophase I

Meiosis I stage with five events: leptotene, zygotene, pachytene, diplotene, diakinesis; homologous chromosomes pair (synapsis) and crossing over occurs.

Leptotene

Early prophase I; chromosomes begin condensing and become visible.

Zygotene

Synapsis begins; homologous chromosomes pair to form bivalents (tetrads).

Pachytene

Crossing over occurs between homologous chromosomes; recombination and genetic variation increase.

Diplotene

Synaptonemal complex dissolves; homologs begin to separate but remain connected at chiasmata.

Diakinesis

Chromosomes condense further; nuclear envelope fragments; spindle fibers attach to tetrads.

Metaphase I

Tetrads align at the metaphase plate; spindle fibers attach to homologous chromosome pairs; nuclear envelope disintegrates.

Anaphase I

Homologous chromosomes separate and move to opposite poles; sister chromatids stay joined.

Telophase I

Cytoplasm divides; nuclear envelope forms around each chromosome set; results in two haploid cells.

Cytokinesis I

Cytoplasm divides to form two haploid daughter cells (each still with duplicated chromosomes).

Meiosis II

Second division separating sister chromatids to form four haploid cells.

Prophase II

Meiosis II prophase; similar to mitotic prophase but with haploid chromosome sets.

Metaphase II

Chromosomes align at the metaphase plate; spindle fibers attach to kinetochores.

Anaphase II

Sister chromatids separate and move to opposite poles.

Telophase II

Nuclear envelopes reform around each set of chromosomes; four haploid daughter cells formed.

Cytokinesis II

Cytoplasm divides to produce four haploid gametes from the two cells produced in Meiosis I.

Homologous chromosomes

Pairs of chromosomes containing the same genes; one from each parent; pair during meiosis I.

Sister chromatids

Identical copies of a chromosome held together at the centromere; separated during anaphase II.

Crossing over

Exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I.

Chiasma

X-shaped site where crossing over occurs between homologous chromosomes.

Synaptonemal complex

Protein structure that forms between homologous chromosomes during prophase I to facilitate pairing.

Tetrad

Pair of homologous chromosomes (each with two sister chromatids) synapsed together during meiosis I.

Synapsis

Pairing of homologous chromosomes during meiosis I.

Reduction division

Meiosis I; chromosome number is halved.

Equational division

Meiosis II; sister chromatids separate, producing four haploid cells.

Gametes

Haploid reproductive cells (sperm and egg) formed by meiosis.

Haploid

Cell with a single set of chromosomes (n).

Diploid

Cell with two sets of chromosomes (2n).

Binary Fission

A simple asexual division in prokaryotes where the cell splits into two identical daughter cells.

Prokaryotic cell division

Division in prokaryotes, typically by binary fission; lacks a nucleus.

Karyokinesis

Division of the cell nucleus during mitosis or meiosis.