BIOLOGY 1240 Chapter 11: Meiosis and Sexual Reproduction — Vocabulary Flashcards

Vocabulary flashcards covering key terms and definitions from the Meiosis and Sexual Reproduction lecture notes.

Meiosis

A two-part cell division that reduces the chromosome number by half to form haploid gametes (Meiosis I and Meiosis II).

Mitosis

Nuclear division producing two genetically identical diploid daughter cells; preserves chromosome number.

Haploid (n)

A cell with one complete set of chromosomes.

Diploid (2n)

A cell with two complete sets of chromosomes; typical of somatic cells.

Gamete

A sex cell (sperm or egg) produced by meiosis in the gonads.

Fertilization

Union of sperm and egg to form a zygote.

Zygote

Diploid cell formed after fertilization; beginning of a new organism.

Crossing over

Exchange of genetic material between non-sister chromatids during Prophase I.

Chiasmata

Visible crossover points where chromatids exchange material during crossing over.

Tetrad

Structure of four chromatids (two homologous chromosomes) aligned during Prophase I.

Synaptonemal complex

Protein lattice that holds homologous chromosomes together during synapsis in Prophase I.

Synapsis

Pairing of homologous chromosomes during Prophase I.

Homologous chromosomes

Chromosome pairs containing the same genes, one from each parent.

Sister chromatids

Identical copies of a chromosome held together at the centromere after replication.

Kinetochore

Protein structure at the centromere where microtubules attach.

Metaphase plate

Equatorial plane where chromosomes align during metaphase.

Prophase I

First meiosis stage; chromosomes condense, homologs pair, crossing over occurs.

Prometaphase I

Nuclear envelope breaks down; spindle forms; kinetochores attach; chiasmata hold homologs together.

Metaphase I

Tetrads align at the cell equator; maternal and paternal chromatids orient randomly.

Anaphase I

Homologous chromosomes separate; sister chromatids remain attached at centromeres.

Telophase I

Chromosomes reach poles; cytokinesis occurs; interkinesis may follow before meiosis II.

Interkinesis

Period between Meiosis I and Meiosis II with no S phase; no DNA replication.

Meiosis II

Second division; sister chromatids separate to form four haploid cells.

Prophase II

Chromosomes recondense (if needed); spindle forms; centrosomes migrate to poles.

Prometaphase II

Nuclear envelope disappears; spindle forms; kinetochores attach to chromatids.

Metaphase II

Chromosomes align at the metaphase plate; sister chromatids orient toward opposite poles.

Anaphase II

Sister chromatids separate and move to opposite poles.

Telophase II

Nuclei form around chromosomes; cytokinesis yields four haploid cells.

Interphase

G1, S, G2 phases; chromosome replication occurs before mitosis or meiosis.

Cleavage furrow

Indentation that leads to cytokinesis in animal cells.

Somatic cells

Body (non-reproductive) cells; typically diploid.

Autosomes

Non-sex chromosomes; humans have 22 pairs besides sex chromosomes.

Sex chromosomes

Chromosomes that determine sex (X and Y in humans).

Germ cells

Cells in the gonads that give rise to gametes; divide by mitosis to self-renew and by meiosis to form gametes.

Primary oocyte

Diploid ovarian cell that begins meiosis I to eventually form an egg.

Primary spermatocyte

Diploid testicular cell that begins meiosis I to form sperm.

Ova/Egg

Female gametes produced by oogenesis.

Sperm

Male gamete produced by spermatogenesis.

Haploid-dominant life cycle

Life cycle where the organism is mostly haploid; zygote is briefly diploid and meiosis yields haploid spores.

Diploid-dominant life cycle

Life cycle where the organism is mostly diploid; meiosis produces haploid gametes that fuse to form a diploid zygote.

Alternation of generations

Life cycle with both haploid (gametophyte) and diploid (sporophyte) multicellular stages; meiosis produces spores in the sporophyte.

Gametophyte

Haploid multicellular stage that produces gametes by mitosis.

Sporophyte

Diploid multicellular stage that produces spores by meiosis.

Spores

Haploid reproductive cells produced by meiosis in the sporophyte that grow into the gametophyte by mitosis.

Zygospore

Diploid resting spore formed after zygote fusion; can germinate into new haploid organisms.