chapter 10 cell reproduction

Cancer

A collection of diseases caused by uncontrolled cell growth that begins when a gene mutation gives rise to a faulty protein involved in cell reproduction.

Proto-oncogene

A normal gene that codes for positive cell-cycle regulators and, when mutated in certain ways, becomes an oncogene.

Oncogene

A mutated version of a normal gene involved in the positive regulation of the cell cycle that leads to an increased rate of cell-cycle progression and can cause a cell to become cancerous.

Tumor Suppressor Gene

A segment of DNA that codes for negative regulator proteins that, when activated, can prevent the cell from undergoing uncontrolled division.

p53

A cell-cycle regulatory protein that monitors DNA damage at the $G_1$ checkpoint, halts cycle progression, activates repair enzymes, or triggers apoptosis; mutated in more than $50\%$ of all human tumor cells.

p21

A cell-cycle regulatory protein that halts cell-cycle progression by blocking Cdk activation, whose production is triggered by p53.

Retinoblastoma Protein (Rb)

A negative cell-cycle regulatory molecule that exerts its effects by interacting with the transcription factor E2F to halt progression until certain events are completed.

Apoptosis

Programmed cell death triggered by a functional regulatory protein (such as p53) when DNA damage in a cell is deemed unsalvageable.

Binary Fission

The process of cell division in prokaryotes that produces two daughter cells that are genetically identical to the parent cell without requiring karyokinesis.

FtsZ

A tubulin-like cytoskeletal protein (filamenting temperature-sensitive mutant Z) that forms a ring at the midpoint of a dividing prokaryotic cell to direct partition and septum formation.

Origin (ORI)

The region of the circular prokaryotic chromosome close to the membrane attachment site where bidirectional DNA replication begins.

Septum

A dividing structure formed in a bacterial cell between daughter nucleoids by the accumulation of membrane and cell wall materials, extending from the periphery toward the center.

Cell-Cycle Checkpoint

An internal surveillance mechanism that monitors the preparedness of a eukaryotic cell to advance through the various stages of the cell cycle.

Cyclin

A regulatory protein whose concentration fluctuates throughout the cell cycle and that binds to cyclin-dependent kinases to phosphorylate key target proteins.

Cyclin-Dependent Kinase (Cdk)

A protein kinase that helps regulate the cell cycle by phosphorylating other target proteins when bound to a specific cyclin partner.

Interphase

The extended preparatory period of the cell cycle leading up to mitosis, subdivided into $G_1$, $S$, and $G_2$ phases.

$G_1$ Phase

The first phase of interphase (first gap) centered on cell growth before DNA replication.

S Phase

The second stage of interphase (synthesis) during which genomic DNA replication occurs.

$G_2$ Phase

The third phase of interphase (second gap) during which the cell undergoes final preparations for mitosis.

$G_0$ Phase

A distinct phase separate from $G_1$ of interphase in which a cell is quiescent and not actively preparing to divide.

Quiescent

Describes a cell that is performing normal cellular functions and has not initiated preparations for division.

Karyokinesis

The mitotic nuclear division process during which duplicated chromosomes are separated into two identical nuclei.

Prophase

The stage of mitosis during which chromosomes condense and the mitotic spindle begins to assemble.

Prometaphase

The stage of mitosis during which the nuclear membrane breaks down and mitotic spindle fibers attach to kinetochores.

Metaphase

The stage of mitosis during which condensed chromosomes align along the equatorial metaphase plate midway between the spindle poles.

Metaphase Plate

The equatorial plane located midway between the two poles of a cell where chromosomes align during metaphase.

Anaphase

The stage of mitosis during which sister chromatids are separated from each other and pulled toward opposite poles.

Telophase

The stage of mitosis during which separated chromosomes reach opposite poles, decondense, and are enclosed within new nuclear envelopes.

Cytokinesis

The physical division of the cytoplasm following mitosis that partitions the contents into two daughter cells.

Cleavage Furrow

A constriction formed by a contracting actin ring during cytokinesis in animal cells that leads to cytoplasmic division.

Cell Plate

A structure formed during cytokinesis in plant cells by Golgi vesicles fusing at the metaphase plate, eventually giving rise to separating cell walls.

Diploid

A cell, nucleus, or organism containing two complete sets of chromosomes ($2n$), such as the $46$ chromosomes in human somatic cells.

Haploid

A cell, nucleus, or organism containing one complete set of chromosomes ($n$), such as human gametes with $23$ chromosomes.

Histone

A conserved, basic, low-molecular-weight protein found in eukaryotic chromatin that associates with DNA to form nucleosomes.

Nucleosome

A structural subunit of chromatin composed of a short length of DNA wrapped around a core of histone proteins.

Condensin

A complex of proteins that assists in the coiling and compaction of sister chromatids during prophase.

Centromere

The constricted region of a condensed chromosome where sister chromatids are bound together.

Kinetochore

A specialized protein structure located at the centromere of each sister chromatid that attracts and binds mitotic spindle microtubules.

Chromatid

A single DNA molecule composed of two strands of duplicated DNA and associated proteins held together with its sister copy at the centromere.

Mitotic Spindle

An apparatus constructed from microtubules that orchestrates and directs chromosome movement during mitosis.

Cancer

A group of diseases caused by uncontrolled cell growth resulting from a breakdown of the regulatory mechanisms that control the cell cycle.

Proto-oncogene

A normal cell gene that codes for positive cell-cycle regulators and, when mutated in certain ways, becomes an oncogene.

Oncogene

A mutated version of a normal gene involved in the positive regulation of the cell cycle that leads to an increased rate of cell-cycle progression.

Tumor Suppressor Gene

A segment of DNA that codes for negative regulator proteins that, when activated, can prevent the cell from undergoing uncontrolled division.

Retinoblastoma Protein (Rb)

A regulatory molecule that exhibits negative effects on the cell cycle by interacting with a transcription factor (E2F).

p53

A cell-cycle regulatory protein that monitors DNA damage and regulates cell growth at the $G_1$ checkpoint; it halts cell-cycle progression upon detecting damage, recruits repair enzymes, or triggers apoptosis.

p21

A cell-cycle regulatory protein that inhibits the cell cycle by blocking Cdk activation; its production is controlled by p53.

Apoptosis

Programmed cell death triggered by functional p53 when genomic DNA damage is deemed unsalvageable.

Binary Fission

The prokaryotic cell division process that produces two daughter cells that are genetically identical to the parent cell.

Nucleoid Region

The specific intracellular area where the single, circular DNA chromosome of a bacterium is packed and located.

Origin (ORI)

The region of the prokaryotic chromosome where bidirectional DNA replication begins, situated close to the binding site of the chromosome to the plasma membrane.

FtsZ

A tubulin-like cytoskeletal protein (filamenting temperature-sensitive mutant Z) that forms a ring around the midpoint of an elongated prokaryote to direct partition and septum formation during cytokinesis.

Septum

A structure formed between daughter nucleoids in a dividing bacterial cell, extending inward from the periphery toward the center to construct the separating cell walls.

Anaphase

The stage of mitosis during which sister chromatids are separated from each other.

Cell Plate

A structure formed during plant cell cytokinesis by Golgi vesicles fusing at the metaphase plate (phragmoplast), ultimately leading to cell walls separating daughter cells.

Cell-Cycle Checkpoint

An internal surveillance mechanism that monitors the preparedness of a eukaryotic cell to advance through the various stages of the cell cycle.

Centriole

A rod-like structure constructed of microtubules located at the center of each animal cell centrosome.

Centromere

A constricted area in condensed chromosomes where sister chromatids are bound together.

Chromatid

A single DNA molecule composed of two strands of duplicated DNA and associated proteins held together at the centromere.

Cleavage Furrow

A constriction formed by an actin ring during cytokinesis in animal cells that leads to cytoplasmic division.

Condensin

Proteins that help sister chromatids coil and compact during prophase.

Cyclin

One of a group of proteins whose concentrations fluctuate throughout the cell cycle; they bind to cyclin-dependent kinases to help regulate the cycle via phosphorylation of key proteins.

Cyclin-Dependent Kinase (Cdk)

A protein kinase that regulates the cell cycle when bound to cyclin by phosphorylating target proteins to activate or inactivate them.

Cytokinesis

The division of the cytoplasm following mitosis that results in the formation of two separate daughter cells.

Diploid

A cell, nucleus, or organism containing two complete sets of chromosomes ($2n$).

$G_0$ Phase

A distinct phase from the $G_1$ phase of interphase in which a cell is quiescent and not preparing to divide.

$G_1$ Phase

The first phase of interphase (first gap) centered on cell growth during mitosis.

$G_2$ Phase

The third phase of interphase (second gap) during which the cell undergoes final preparations for mitosis.

Gamete

A haploid reproductive cell or sex cell (such as a sperm, pollen grain, or egg) containing one set of chromosomes ($n$).

Gene

The physical and functional unit of heredity; a sequence of DNA that codes for a specific protein or RNA molecule.

Genome

The total genetic information contained within a cell or organism.

Haploid

A cell, nucleus, or organism containing one single set of chromosomes ($n$).

Histone

One of several conserved, low-molecular-weight basic proteins found in eukaryotic chromatin that associates with DNA to form nucleosomes.

Homologous Chromosomes

Pairs of matched chromosomes possessing identical morphology and genes at the same loci, with one homolog derived from each parent.

Interphase

The preparatory period of the cell cycle leading up to mitosis, comprising the $G_1$, $S$, and $G_2$ phases.

Karyokinesis

The process of mitotic nuclear division.

Kinetochore

A protein structure associated with the centromere of each sister chromatid that binds spindle microtubules during prometaphase.

Locus

The physical location of a gene on a chromosome.

Metaphase

The stage of mitosis during which condensed chromosomes are aligned at the metaphase plate.

Metaphase Plate

The equatorial plane situated midway between the two cell poles where chromosomes align during metaphase.

Mitosis

The period of the cell cycle during which duplicated chromosomes are separated into identical nuclei; composed of prophase, prometaphase, metaphase, anaphase, and telophase.

Mitotic Phase

The phase of the cell cycle in which duplicated chromosomes are separated into two nuclei and cytoplasmic contents divide; encompasses karyokinesis and cytokinesis.

Mitotic Spindle

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

Nucleosome

A subunit of chromatin composed of a short length of DNA wrapped around an octameric core of histone proteins.

Prometaphase

The mitotic stage during which the nuclear envelope breaks down and spindle microtubules attach to kinetochores.

Prophase

The initial stage of mitosis during which chromosomes condense and the mitotic spindle begins to assemble.

Quiescent

Refers to a metabolically active cell in $G_0$ that is performing normal cellular functions without initiating preparations for division.

$S$ Phase

The synthesis stage of interphase during which DNA replication occurs.

Telophase

The mitotic stage during which separated chromosomes reach opposite poles, decondense, and are enclosed within new nuclear envelopes.

Cell Cycle

An orderly sequence of events describing the stages of a cell's life from the division of a single parent cell to the production of two new genetically identical daughter cells.

Genome

A cell's total DNA packaged as a double-stranded DNA molecule.

Nucleoid

The central region in a prokaryotic cell that contains its single, circular double-stranded DNA genome.

Plasmids

Small loops of non-essential double-stranded DNA found in some prokaryotes that can be exchanged between bacteria, often carrying traits such as antibiotic resistance.

Somatic Cells

Human body cells that contain two matched sets of chromosomes (46 chromosomes in humans), possessing a diploid configuration.

Gametes

Human sex cells (sperm or eggs) containing one set of 23 chromosomes, designated as haploid ($1n$).

Diploid

A cellular configuration designated as $2n$ containing two matched or homologous sets of chromosomes, one from each biological parent.

Haploid

A cellular configuration designated as $1n$ containing only one set of chromosomes.

Homologous Chromosomes

Matched pairs of chromosomes in a diploid organism that are identical in length and carry genes in exactly the same locus.

Locus

The specific physical location of a nucleotide segment or gene on a chromosome.

Genes

Functional units of chromosomes that determine specific characteristics by coding for specific proteins.