BIOL212 Ch12-13

Comprehensive vocabulary flashcards covering the key terms, molecular mechanisms, phases, and genetic outcomes of cell division, mitosis, the cell cycle control system, and meiosis.

Genome

The complete complement of an organism's or virus's genes along with its noncoding nucleic acid sequences; in prokaryotes, it often consists of a single DNA molecule, whereas in eukaryotes it typically consists of multiple DNA molecules.

Chromosomes

Cellular structures consisting of one very long DNA molecule and associated proteins that pack several hundred to a few thousand genes within eukaryotic nuclei.

Chromatin

The complex of DNA and protein that makes up eukaryotic chromosomes and condenses into discrete visible chromosomes during cell division.

Somatic cells

All body cells of a multicellular eukaryotic organism except reproductive cells and their precursors, possessing two sets of chromosomes ($2n = 46$ in humans).

Gametes

Haploid reproductive cells (such as sperm and eggs) that contain half the chromosome complement of somatic cells ($n = 23$ in humans).

Sister chromatids

Two joined copies of an original duplicated chromosome that are held together along their lengths by cohesin protein complexes.

Centromere

The constricted region of a duplicated chromosome where the two sister chromatids are most closely attached to each other.

Mitosis

The division of the genetic material in the eukaryotic nucleus, conventionally broken down into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.

Cytokinesis

The division of the cytoplasm to form two separate, genetically identical daughter cells immediately following mitosis or meiosis.

Interphase

The period of the eukaryotic cell cycle between cell divisions, accounting for approximately $90\%$ of the cycle, during which the cell grows and copies its chromosomes.

S phase

The synthesis subphase of interphase during which cell growth, metabolic activity, and precise replication of chromosomal DNA take place.

Walther Flemming

The German anatomist who developed specialized dyes in 1882 to observe and track the behavior of chromosomes during mitosis and cytokinesis.

Mitotic spindle

An apparatus composed of microtubules and associated proteins that orchestrates chromosome movement during mitosis.

Centrosome

A subcellular structure functioning as a microtubule-organizing center in animal cells that duplicates during interphase to establish the two spindle poles.

Aster

A radial array of short microtubules extending outward from each centrosome toward the cell cortex.

Kinetochore

A complex of proteins assembled at each centromere of a chromosome that serves as the attachment site for spindle microtubules during prometaphase.

Metaphase plate

An imaginary plane equidistant between the two spindle poles along which chromosomes align during metaphase.

Separase

An enzyme that cleaves the cohesin proteins linking sister chromatids during anaphase, enabling chromatid separation.

"Pac-man" mechanism

A model of chromosome movement during anaphase where motor proteins located on the kinetochore walk along microtubules while depolymerizing them at their kinetochore ends.

Cleavage furrow

A shallow contractile groove appearing in the cell membrane near the old metaphase plate in animal cells, signaling the onset of cytokinesis.

Cell plate

A membrane-bound structure assembled across the midline of a dividing plant cell from coalescing vesicles, which eventually gives rise to a new cell wall.

Binary fission

The mode of asexual cell division in prokaryotes (bacteria and archaea) where the circular chromosome replicates and the cell divides into two daughter cells.

Origin of replication

The specific site on a bacterial chromosome where DNA synthesis initiates during binary fission.

Cyclin

A regulatory cellular protein whose cyclic fluctuations in concentration control the activation of cyclin-dependent kinases throughout the cell cycle.

Cyclin-dependent kinases (Cdks)

Enzymes that control the cell cycle via phosphorylation and require association with an appropriate cyclin molecule to become enzymatically active.

Maturation-promoting factor (MPF)

A cyclin-Cdk complex that phosphorylates various target proteins to trigger a cell's transition past the $G_2$ checkpoint into M phase.

$G_0$ phase

A non-dividing state exited to by eukaryotic cells that fail to receive a go-ahead signal at the $G_1$ checkpoint.

Heredity

The biological transmission of traits from parent organisms to their offspring from one generation to the next; also called inheritance.

Genetics

The scientific discipline focused on the study of heredity and inherited variation.

Gene

A discrete unit of hereditary information composed of a specific sequence of nucleotides in DNA.

Locus

The specific physical position or address of a gene along the length of a chromosome.

Karyotype

An ordered microscopic display of an individual's pairs of condensed metaphase chromosomes arranged by length, centromere position, and banding pattern.

Homologous chromosomes (Homologs)

A matched pair of chromosomes carrying genes for the same inherited characters, with one chromosome inherited from the maternal parent and one from the paternal parent.

Sex chromosomes

Chromosomes that determine biological sex, designated as X and Y in humans ($\text{XX}$ in females, $\text{XY}$ in males).

Autosomes

Any chromosomes that are not sex chromosomes; humans possess $22$ pairs of autosomes ($44$ total).

Diploid cell

A cell containing two complete sets of chromosomes ($2n$), representing one set from each biological parent ($2n = 46$ in humans).

Haploid cell

A cell containing only a single set of chromosomes ($n$), such as a sperm or egg cell ($n = 23$ in humans).

Fertilization

The fusion of haploid male and female gametes to form a diploid single-celled zygote.

Zygote

The diploid cell resulting from the union of two haploid gametes during fertilization, which develops into a multicellular organism via mitosis.

Meiosis

A two-stage reduction division (meiosis I and meiosis II) in sexually reproducing organisms that converts one diploid cell into four genetically distinct haploid daughter cells.

Synapsis

The close physical pairing and association of homologous chromosomes along their lengths 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.

Chiasmata

X-shaped anatomical regions visible under microscopy where homologous nonsister chromatids have exchanged segments during crossing over.

Recombinant chromosomes

Individual chromosomes generated by crossing over that carry combined segments of DNA derived from two different parents.

Independent assortment

The random orientation and segregation of maternal and paternal homologous chromosome pairs at the metaphase I plate, producing $2^n$ possible gametic combinations.

Random fertilization

A mechanism generating genetic variation wherein any sperm can fuse with any ovum, producing approximately $70\text{ trillion}$ possible diploid combinations in humans.

Bdelloid rotifer

An anhydrobiotic, asexually reproducing microscopic animal that generates genetic diversity without meiosis by absorbing and incorporating foreign DNA from its environment.