Mitosis Part 2 and Cancer

Vocabulary practice flashcards covering cell cycle phases, checkpoints, mitosis, cancer progression, HeLa cells, genetic risk factors, and telomere dynamics.

Prophase

The mitotic stage during which chromatin condenses into visible chromosomes and the cell nucleus disappears.

Metaphase

The stage of mitosis during which chromosomes align along the central metaphase plate.

Anaphase

The stage of mitosis in which sister chromatids separate and chromosomes move toward opposite spindle poles.

Telophase

The final stage of mitosis during which cells divide and the cycle resets; animal cells undergo cleavage, whereas plant cells form a cell plate.

Cell Plate

A dividing structure that forms during plant cell cytokinesis because the presence of a rigid cell wall prevents animal-style cleavage furrow formation.

Interphase

The interval between successive mitotic divisions, encompassing gap phases ($G_1$, $G_2$) and the DNA synthesis ($S$) phase.

Gap Phase

A cell cycle period during which the cell recovers from its previous phase and performs its native function; there are three gap phases ($G_1$, $G_2$, and $G_0$).

$G_1$ Phase (Gap Phase 1)

The primary growth phase of the cell cycle where the cell reestablishes its native cellular functions prior to DNA replication.

$S$ Phase (Synthesis Phase)

The cell cycle phase where DNA replication occurs, effectively doubling the amount of DNA from $1\times$ to $2\times$.

$G_2$ Phase (Gap Phase 2)

The gap phase following DNA synthesis during which the cell resumes native functions and prepares for cell division.

Cell Cycle DNA Fluctuations

The pattern where DNA content is $1\times$ in $G_1$, rises continuously during the $S$ phase to $2\times$, stays at $2\times$ throughout $G_2$ and mitosis ($M$), and cuts in half back to $1\times$ after cytokinesis.

Cell Cycle Checkpoints

Programmed regulatory pathways that halt progression through the cell cycle if abnormalities are detected (such as damaged DNA, single-stranded uncopied DNA, lack of sufficient nucleotides/nutrients, or chromosome misalignment at the metaphase plate).

$G_0$ Phase (Gap Phase 0)

A resting state where a cell exits the active division cycle while maintaining normal cellular function; most cells in the adult human body reside in this phase.

Senescence

A permanent state in which a cell ceases dividing but remains metabolically active.

Apoptosis

A programmed, active self-destruction process in which a cell expresses digestive enzymes to feed neighboring cells, serving as protection against viral spread and cancer.

Cancer

A group of roughly $200$ diseases characterized by inappropriate or uncontrolled cell division or insufficient programmed cell death, with a lifetime human risk of approximately $40\%$.

Leukemia

A cancer characterized by the overproduction of abnormal white blood cells.

Teratoma

A type of tumor that develops with multiple distinct tissue types (often containing teeth, hair, and other complex tissue structures).

Meningioma

A solid tumor that forms in the meninges of the brain.

Tumor

An abnormal mass of tissue that forms when cells grow and divide more than they should or fail to die when they are supposed to.

Metastasis

The spread of cancer cells from their primary site of origin to distant areas of the body via the vascular or lymphatic systems, commonly reseeding in the liver and lungs.

HeLa Cells

The first immortal human cell line, derived from a cervical tumor biopsy of Henrietta Lacks in 1951; known for doubling every $24\text{ hours}$, resisting apoptosis, and dividing indefinitely.

Inherited Mutations

Germline genetic alterations passed down from parents that do not typically trigger cancer directly on their own, but increase an individual's susceptibility to developing cancer.

De Novo Mutations

New genetic alterations arising spontaneously in an individual rather than being inherited from parents.

BRCA1 (BReast CAncer gene 1)

A critical tumor suppressor gene whose protein repairs DNA damage and arrests the cell cycle; mutations impair this function, elevating lifetime breast cancer risk from $12.5\%$ to $60\% - 72\%$ and ovarian cancer risk from $1.1\%$ to $39\% - 58\%$.

Telomeres

Repetitive non-coding nucleotide sequences ($5'\text{-TTAGGG-}3'$) located at chromosome ends that shorten with each cell division cycle, serving as an internal cellular clock that triggers cell death once depleted.

Telomerase

A specialized enzyme found in germ cells and some stem cells that lengthens telomeric ends, effectively resetting the cellular division limit.