BIOL212 Ch12-13

Vocabulary terms and definitions from Campbell Biology Twelfth Edition covering cell division, mitosis, meiosis, and sexual life cycles.

Genome

All the DNA in a cell; it can consist of a single DNA molecule (common in prokaryotes) or a number of DNA molecules (common in eukaryotes).

Chromatin

The complex of DNA and protein that condenses during cell division to form eukaryotic chromosomes.

Somatic Cells

All body cells of an organism except gametes and their precursors; nonreproductive cells that contain two sets of chromosomes ($2n$).

Gametes

Reproductive cells (sperm and eggs) that contain half as many chromosomes as somatic cells ($n$).

Sister Chromatids

Two joined copies of the original duplicated chromosome attached along their lengths by cohesins.

Cohesins

Protein complexes that attach sister chromatids together along their lengths.

Centromere

The narrow "waist" of a duplicated chromosome where two sister chromatids are most closely attached.

Mitosis

The division of the genetic material in the nucleus of eukaryotic cells.

Cytokinesis

The division of the cytoplasm that follows mitosis, producing two distinct daughter cells.

Meiosis

A variation of cell division that yields nonidentical daughter cells containing half as many chromosomes as the parent cell.

Interphase

The phase of the cell cycle occupying about $90\%$ of the time, in which the cell grows and copies its chromosomes in preparation for cell division.

S Phase

The subphase of interphase during which metabolic activity, growth, and DNA synthesis (chromosome duplication) occur.

Mitotic Spindle

A structure composed of microtubules that controls chromosome movement during eukaryotic cell division.

Centrosome

A type of microtubule-organizing center in animal cells that replicates during interphase to organize the spindle apparatus poles.

Aster

A radial array of short microtubules extending outward from each centrosome.

Kinetochore

A protein complex associated with the centromere of each sister chromatid where spindle microtubules attach.

Metaphase Plate

An imaginary plane midway between the spindle's two poles along which chromosomes align at metaphase.

Separase

An enzyme that cleaves cohesins during anaphase, allowing sister chromatids to separate.

Cleavage Furrow

A shallow groove in the animal cell surface near the old metaphase plate that forms during cytokinesis.

Cell Plate

A membrane-bound structure formed by vesicles during cytokinesis in plant cells that develops into a new cell wall.

Binary Fission

The type of cell division by which prokaryotes (bacteria and archaea) reproduce asexual offspring by replicating their chromosome and pinching the plasma membrane inward.

Origin of Replication

The specific site on a bacterial chromosome where chromosome replication begins during binary fission.

Cell Cycle Control System

A cyclically operating set of molecules in the cell that triggers and coordinates key events of the cell cycle through regulated checkpoints.

Cyclins

Regulatory proteins that exhibit cyclically fluctuating concentrations in the cell and attach to Cdks to control cell cycle progression.

Cyclin-Dependent Kinases (Cdks)

Protein kinases that regulate the cell cycle and require attachment to a cyclin partner to become active.

Maturation-Promoting Factor (MPF)

A cyclin-Cdk complex that triggers a cell's passage past the $G_2$ checkpoint into the mitotic ($M$) phase.

Genetics

The scientific study of heredity and inherited variation.

Gene

A hereditary unit consisting of a specific segment of DNA packaged into chromosomes.

Locus

A gene's specific physical location along the length of a chromosome.

Karyotype

An ordered display of the chromosome pairs from a cell arranged by size, centromere position, and banding pattern.

Homologous Chromosomes (Homologs)

A pair of chromosomes having the same length, centromere position, and staining pattern, possessing genes for the same inherited characters.

Sex Chromosomes

The chromosomes ($X$ and $Y$ in humans) that determine an individual's biological sex.

Autosomes

All chromosomes that are not sex chromosomes; in human somatic cells, the 22 non-sex chromosome pairs.

Diploid Cell

A cell containing two sets of chromosomes ($2n$); in humans, the diploid number is $2n = 46$.

Haploid Cell

A cell containing a single set of chromosomes ($n$); in humans, the haploid number is $n = 23$.

Fertilization

The union of haploid gametes (sperm and egg) that re-establishes pairs of homologous chromosomes.

Zygote

A diploid fertilized egg resulting from the fusion of sperm and ovum that divides by mitosis to develop into a multicellular adult.

Chiasmata

X-shaped regions on homologous chromosomes that represent the physical sites where crossing over occurred.

Synapsis

The physical pairing and intimate association of homologous chromosomes during prophase I of meiosis.

Crossing Over

The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.

Recombinant Chromosomes

Individual chromosomes that result from crossing over, combining DNA inherited from each parent.

Alleles

Alternative versions of a gene created originally by mutations.