The Cell Cycle, Chromosomes, and Cancer Regulation

Vocabulary practice flashcards covering cell cycle stages, chromosome organization, cell division checkpoints, and molecular regulators such as cyclins, Cdks, and p53.

Particulate Matter ($PM_{2.5}$)

Fine air pollution particles that act as carcinogens by triggering inflammation, which awakens dormant cancer cells.

Gene

A specific segment of DNA along a chromosome that contains instructions governing a particular inherited trait, such as eye color or hair color.

Locus (Loci)

The specific physical location or address of a particular gene on a chromosome.

Diploid ($2N$)

A cellular state or cell containing two chromosomes of each type ($2n = 46$ in humans), with one set inherited from each parent.

Haploid ($N$)

A cellular state characteristic of gametes (sperm and eggs) containing only one chromosome of each type ($n = 23$ in humans).

Chromatin

The loosely coiled complex consisting of approximately $40\%$ DNA and $60\%$ histone proteins present in the eukaryotic nucleus prior to condensed division.

Chromosome Compaction

The multi-tiered folding process in which DNA ($2\,\text{nm}$) wraps around histones to form nucleosomes ($11\,\text{nm}$), coiling into $30\,\text{nm}$ fibers, forming $300\,\text{nm}$ looped chromatin, $700\,\text{nm}$ condensed chromatin, and finally a fully condensed $1{,}400\,\text{nm}$ visible chromosome.

Homologous Chromosomes

Pairs of matching chromosomes of the same type within a diploid cell, consisting of one maternal chromosome and one paternal chromosome.

Human Karyotype

The visual display and organization of an individual's complete set of $46$ chromosomes arranged into $23$ pairs, including autosomes and sex chromosomes ($X$ and $Y$).

Cell Division

The biological process by which a cell duplicates into more cells, fulfilling essential roles in growth, cell replacement, healing, and reproduction.

Cell Cycle

An orderly set of recurring stages occurring between one division and the next, categorized into Interphase and the Mitotic ($M$) phase.

Interphase

The predominant phase occupying approximately $90\%$ of the cell cycle during which the cell grows, synthesizes materials, and replicates its genetic material.

$G_1$ Phase (Gap 1)

The initial growth phase of interphase where the cell recovers from previous division, doubles its organelles, and accumulates materials needed for DNA synthesis.

$S$ Phase (Synthesis)

The interphase period characterized by DNA replication, in which chromosomes enter with $1$ chromatid each and exit with $2$ identical chromatids each.

$G_2$ Phase (Gap 2)

The interphase period occurring between DNA replication and the onset of mitosis, during which the cell synthesizes proteins necessary for division.

$G_0$ Phase

A resting state of the cell cycle occupied by cells that have halted cell division and are not actively dividing.

Mitosis

The process of nuclear division within the $M$ phase that distributes duplicated daughter chromosomes into two separate, identical daughter nuclei.

Cytokinesis

The cytoplasmic division step of the $M$ phase that divides the cytoplasm to yield two genetically identical daughter cells.

Cell Cycle Checkpoints

Specific regulatory transition points in the cell cycle where molecular signals inspect conditions and halt or proceed with division.

DNA Damage Checkpoint ($G_1$ Checkpoint)

The most important cell cycle checkpoint, located prior to entering the $S$ phase, which evaluates whether DNA is damaged and can redirect the cell into $G_0$.

DNA Replication Checkpoint ($G_2$ Checkpoint)

The checkpoint located at the end of the $G_2$ phase before mitosis that verifies whether all DNA has been completely and accurately replicated.

Spindle Assembly Checkpoint ($M$ Checkpoint)

The mitotic checkpoint occurring before anaphase (at the end of metaphase) that ensures all chromosomes are properly attached to the spindle fibers.

$$p53$$

A tumor suppressor protein that arrests the cell cycle at the $G_1/S$ transition upon detecting damaged DNA, giving the cell sufficient time to repair the DNA.

Cyclins

Cellular regulatory proteins whose concentrations rise and fall in a cyclical manner during the cell cycle to bind and activate cyclin-dependent kinases.

Cyclin-Dependent Kinases (Cdks)

Enzymes that become activated when bound to specific cyclins, subsequently phosphorylating target proteins that advance cell cycle transitions.

Maturation Promoting Factor (MPF)

A holoenzyme complex formed when cyclin binds with Cdk that phosphorylates proteins needed for mitosis before cyclin is broken down at mitotic completion.