Control of the Cell Cycle and Genetics of Cancer

Vocabulary practice flashcards covering cell cycle regulation, checkpoints, cyclins, CDKs, and the genetics of cancer.

Cyclin

A protein whose concentration rises and falls in synchrony with the cell cycle to help regulate its progression.

Kinase

An enzyme that adds phosphate groups to other proteins (phosphorylates them).

Cyclin-Dependent Kinase (CDK)

A specialized kinase enzyme that must bind to a cyclin protein in order to become activated.

Cyclin-CDK Complex

A molecular pairing formed by a cyclin and a CDK that functions as a key positive driver of cell cycle progression.

Maturation-Promoting Factor (MPF)

A cyclin-CDK complex (comprising Cyclin B and Cdk1/cdc2) discovered in immature frog eggs whose enzymatic phosphorylation activity induces cell division.

cdc2 Gene

A gene identified in yeast mutants that encodes a CDK protein necessary for committing cells to DNA synthesis ('START') and to mitosis.

$G_1/S$ Checkpoint

The primary checkpoint (also called START or restriction point) where the cell decides whether to divide, integrating external signals, cell size, and nutritional status.

$G_2/M$ Checkpoint

The cell cycle control point where the cell commits to entering mitosis after double-checking the accuracy and completion of DNA replication.

Spindle Checkpoint

The late metaphase checkpoint that verifies all chromosomes are properly attached to spindle microtubules at the metaphase plate before allowing anaphase to begin.

Anaphase-Promoting Complex (APC/C)

A complex (also called the cyclosome) that triggers anaphase by destroying the inhibitory protein securin.

Securin

An inhibitory protein that holds separase in an inactive state until it is targeted for destruction by the APC/C.

Separase

An enzyme activated upon securin degradation that cleaves cohesin to allow sister chromatid separation.

Cohesin

A protein complex that acts as the molecular 'glue' holding sister chromatids together until anaphase.

Growth Factor

An extracellular signaling molecule released by cells that stimulates surrounding cells to divide and can override inhibitory division controls.

Proto-oncogene

A normal cellular gene that promotes cell cycle progression; when mutated into an oncogene, only one altered copy is required to drive uncontrolled division.

Oncogene

A mutated, gain-of-function form of a proto-oncogene that causes cancer by continuously stimulating cell division.

Tumor-Suppressor Gene

A gene that normally acts to slow or halt the cell cycle (such as $p53$ or $Rb$); both copies must lose function for a cancerous phenotype to emerge.

Retinoblastoma Susceptibility Gene (Rb)

The first identified tumor-suppressor gene, encoding a protein that binds regulatory proteins to prevent cyclin and CDK production; loss of both copies predisposes to retina tumors.

p53 Gene

A tumor-suppressor gene active at the $G_1$ checkpoint that monitors DNA integrity, pausing division to stimulate repair or triggering apoptosis if damage cannot be repaired.