Meiosis and Cell Division Lecture

Vocabulary practice flashcards covering cell types, chromosome classifications, and the stages and outcomes of Meiosis I and Meiosis II.

Somatic Cells

Body cells found in tissues and organs whose DNA is not passed down to offspring (e.g., nerve cells).

Gametes

Sex cells (eggs in females, sperm in males) whose DNA can be passed to offspring.

Chromosome

A condensed DNA molecule containing part or all of the genetic material of an organism; human cells contain $23$ pairs ($46$ total).

Autosomes

Chromosomes that carry traits unrelated to biological sex, consisting of chromosomes #$1$ through #$22$ in humans.

Sex Chromosomes

Chromosomes containing genes related to biological sex, designated as chromosome pair #$23$ ($X$ and $Y$; $XX$ for genetically classified female and $XY$ for genetically classified male).

Homologous Chromosomes

Two chromosomes that have the same genes in the same order, but may carry different versions (alleles)—one inherited from the mother and one from the father.

Diploid ($2n$)

Cells that contain two copies of each chromosome (possessing homologous pairs), characteristic of somatic cells.

Haploid ($n$)

Cells containing only one copy of each chromosome (lacking homologous pairs), characteristic of gametes.

Fertilization

The union of a sperm ($n$) and an egg ($n$) cell that produces a diploid ($2n$) zygote, restoring the full chromosome count.

Zygote

A fertilized egg with a restored diploid ($2n$) chromosome number formed by the fusion of two haploid gametes.

Mitosis

Cellular division starting with one $2n$ somatic cell and concluding with two identical $2n$ somatic cells.

Meiosis

A specialized two-stage division process starting with one $2n$ cell and ending with four genetically distinct haploid ($n$) gametes.

Crossing Over

The exchange of genetic material between homologous chromosomes during Prophase I of meiosis, creating genetic variation.

Independent Assortment

The random orientation and separation of alleles and homologous chromosome pairs during the first meiotic division that produces genetic variation.

Prophase I

The meiotic stage where chromosomes condense, pair up with their homologous partners to form tetrads, and undergo crossing over.

Metaphase I

The meiotic stage during which homologous chromosome pairs align side by side along the center of the cell.

Anaphase I

The meiotic stage where homologous chromosome pairs are separated and pulled toward opposite poles by spindle fibers.

Telophase I

The meiotic stage that concludes the first division, resulting in two new haploid ($n$) cells with duplicated chromosomes.

Prophase II

The beginning stage of the second meiotic division where the nuclear envelope breaks down and the spindle apparatus forms without any prior DNA replication.

Metaphase II

The meiotic stage where duplicated chromosomes line up in single file (not in pairs) along the middle of the cell.

Anaphase II

The meiotic stage where sister chromatids are pulled apart by spindle fibers toward opposite poles.

Telophase II

The concluding meiotic stage resulting in four genetically distinct haploid ($n$) cells with un-duplicated chromosomes.