Chapter 11: Meiosis & Reproduction

Comprehensive vocabulary flashcards covering the concepts of meiosis, chromosome dynamics, sexual and asexual reproduction, and gametogenesis based on the lecture notes.

Autosomes

All chromosomes in an organism except sex chromosomes; in humans, they constitute pairs 1 through 22.

Sex Chromosomes

Chromosomes that determine the biological sex of an individual; referred to as pair 23 in humans ($XX$ for females and $XY$ for males).

Ploidy

A measure of the total number of sets of chromosomes present within a biological cell.

Diploid ($2n$)

A cellular state containing two complete homologous sets of chromosomes (one maternal and one paternal); in humans, $2n = 46$.

Haploid ($n$)

A cellular state characterized by a single set of unpaired chromosomes, typical of gametes; in humans, $n = 23$.

Meiosis

A reduction division process in sexually reproducing organisms consisting of two successive rounds of cell division that reduces chromosome count from diploid ($2n$) to haploid ($n$), producing four genetically unique gametes.

Meiosis I

The first division of meiosis in which duplicated homologous chromosome pairs are separated, reducing the ploidy level from diploid ($2n$) to haploid ($n$).

Meiosis II

The second division of meiosis in which sister chromatids separate into individual daughter chromosomes without prior DNA replication, yielding four unduplicated haploid ($n$) cells.

Synapsis

The pairing and physical connection of homologous chromosomes along their lengths at the synaptonemal complex during prophase I of meiosis.

Crossing Over

The reciprocal exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I of meiosis.

Recombinant Chromosomes

Individual chromosomes resulting from crossing over that carry unique combinations of genes containing DNA from both parents.

Chiasmata

Visible X-shaped points where non-sister chromatids of homologous chromosomes cross over and remain physically linked during prophase I.

Tetrad

A complex consisting of four chromatids (two homologous chromosomes, each with two sister chromatids) held together by chiasmata during synapsis.

Independent Assortment

The random orientation and distribution of maternal and paternal homologous chromosome pairs along the metaphase plate during meiosis I, yielding $2^n$ possible chromosomal combinations.

Asexual Reproduction

The generation of offspring from a single individual without the fusion of gametes, producing offspring that are genetically identical to the parent and siblings (clones).

Sexual Reproduction

A reproductive process arising from the fusion of two gametes that produces genetically unique offspring with varying combinations of parental genes.

Diploid-Dominant Life Cycle

A life cycle strategy used by humans and most animals where the multicellular adult diploid ($2n$) stage is dominant, and the only haploid ($n$) cells are the gametes.

Gamete

A specialized haploid ($n$) reproductive cell (sperm or egg) produced in the gonads via meiosis that fuses with another gamete during fertilization.

Fertilization

The union of two haploid gametes (sperm and egg, each $n = 23$ in humans) to form a single diploid zygote ($2n = 46$).

Random Fertilization

The mechanism where any genetically unique sperm can fertilize any genetically unique egg, producing approximately $70\text{ trillion}$ possible chromosome combinations in humans ($(2^{23})^2$).

Spermatogenesis

The process of male meiosis that occurs in the seminiferous tubules of the testes, converting diploid spermatogonia into mature haploid spermatozoa.

Primary Spermatocyte

A diploid ($2n$) male germ cell derived from a spermatogonium that undergoes meiosis I to produce two haploid secondary spermatocytes.

Secondary Spermatocyte

A haploid ($n$) male cell formed by meiosis I that undergoes meiosis II to form two haploid spermatids.

Spermatids

The four unduplicated haploid ($n$) cells produced at the end of meiosis II that subsequently differentiate into spermatozoa (mature sperm).

Oogenesis

The process of female meiosis taking place in the ovary that produces one large, functional haploid ovum and two to three non-functional polar bodies.

Primary Oocyte

A diploid ($2n$) female germ cell located in the ovarian cortex that undergoes meiosis I to produce a secondary oocyte and a first polar body.

Secondary Oocyte

The large haploid ($n$) cell produced by unequal cytokinesis during meiosis I of oogenesis that retains most of the cytoplasm and undergoes meiosis II.

Polar Body

A small, non-functional haploid cell produced during the unequal divisions of oogenesis that contains minimal cytoplasm and eventually disintegrates.

DISCO PUG

A comparative mnemonic for Mitosis vs Meiosis assessing Divisions, Independent assortment, Synapsis, Crossing over, Outcome, Ploidy, Use, and Genetics.