BIO123 Chapter 8 - Introduction to Reproduction at the Cellular Level

Vocabulary-style flashcards covering the genome, cell cycle stages, mitosis, meiosis, prokaryotic division, and chromosomal disorders based on the Chapter 8 lecture transcript.

Genome

The DNA of a cell; in prokaryotes it is a single, circular DNA found in the nucleoid, while in eukaryotes it consists of many linear chromosomes.

Chromatin

The structure formed when DNA double helix is wrapped around histone proteins; it condenses into nucleosomes and eventually into chromosomes before cell division.

Interphase

The stage of the cell cycle dedicated to cell maintenance and preparation for division, consisting of $3$ stages: $G_1$, $S$, and $G_2$.

Gap 1 ($G_1$)

The first stage of interphase characterized by normal cell functions like transcription, translation, and cellular respiration in preparation for the rest of the cell cycle.

Synthesis ($S$) Phase

The stage of interphase where DNA is replicated, resulting in single chromosomes being duplicated into sister chromatids attached at a centromere.

Gap 2 ($G_2$)

The final stage of interphase where the cell continues normal functions while specifically preparing for division through energy production and organelle replication.

Centrosomes

Microtubule-organizing centers that form the mitotic spindle; they duplicate in animal cells but are replaced by the cell wall for anchoring in plants.

G0 (Gap 0) Phase

A resting stage for cells that will not replicate, such as human muscle cells which may pause briefly or nerve cells which remain in this phase forever.

Mitosis

A mitotic cycle phase consisting of $5$ stages (prophase, prometaphase, metaphase, anaphase, and telophase) that separate sister chromatids to create two identical cells.

Kinetochore

A protein structure that attaches to each sister chromatid during prometaphase to facilitate movement via the mitotic spindle.

Metaphase Plate

The center area of the cell where chromosomes align during metaphase.

Cytokinesis

The physical splitting of the cell separating two nuclei into identical cells; occurs via a cleavage furrow in animal cells and a cell plate in plant cells.

Binary Fission

The quick and simple process of prokaryotic cell division resulting in identical organisms.

Septum

A wall that forms during prokaryotic cytokinesis to complete the formation of $2$ independent cells.

Asexual Reproduction

Cell division resulting in a new, identical organism; includes budding in multicellular organisms and binary fission in single-cellular organisms.

Sexual Reproduction

Reproduction involving fertilization between two reproductive cells, leading to genetically unique offspring.

Gametes

Haploid germline cells ($1n$), such as egg and sperm in humans, that fuse during fertilization.

Zygote

A diploid somatic cell ($2n$) formed by the fusion of two gametes that begins the process of mitosis.

Homologous Chromosomes

Pairs of chromosomes of the same length with the same types of genes located at specific loci.

Autosomes

Chromosomes numbered $1$ through $22$ in humans that play little to no role in sex determination.

Allosomes

The human $X$ and $Y$ chromosomes; phenotypic males have one $X$ and one $Y$, while females have two homologous $X$ chromosomes.

Tetrad

A structure formed in prophase I of meiosis consisting of two homologous chromosomes, totaling $4$ sister chromatids.

Chiasmata

The points where homologous chromosomes are held together and where crossing over (recombination) occurs during meiosis I.

Independent Assortment

The random arrangement of homologous chromosomes on either side of the metaphase plate, providing a unique set for each division.

Interkinesis

A brief interphase that occurs between meiosis I and meiosis II without an $S$ phase.

Karyotype

The number and visual appearance of the chromosomes in a cell, typically visualized in a chart called a karyogram.

Nondisjunction

An error in meiosis where homologous chromosomes or sister chromatids do not separate properly, resulting in gametes with an incorrect number of chromosomes.

Aneuploid

A condition in which an individual has an error in chromosome number, such as monosomy ($45$ chromosomes) or trisomy ($47$ chromosomes).

Polyploid

An organism with more than the correct number of chromosome pairs; these organisms are typically sterile and cannot perform meiosis.

Inversion

A chromosomal structural rearrangement where a piece of the chromosome is rotated $180$ degrees.

Translocation

The process by which nonhomologous chromosomes exchange different genes.