Cell Division and the Cell Cycle

Flashcards covering the mechanics of binary fission, mitosis, interphase, cell cycle checkpoints, and the biological basis of cancer based on lecture notes.

Genome

All the DNA within a cell.

Plasmids

Small loops of bacterial DNA that are not essential to its survival but can help it get out of a bind; they can be shared via conjugation.

Binary Fission

A form of asexual reproduction where a cell creates a duplicate of its chromosome and divides to create two identical daughter cells.

Diploid ($2n$)

A cell condition where chromosomes occur in pairs; represents the standard chromosome number in somatic cells.

Haploid ($n$)

A cell condition where only one set of chromosomes is present; occurs in gametes and organisms like fungi.

Histone proteins

Regularly placed proteins that prevent the DNA molecule from becoming entangled with itself.

Nucleosome

The association of DNA with histone proteins.

Chromatin

DNA with histones, technically consisting of nucleosomes linked together.

Somatic Cells

Generalized cells that form the body, such as skin, kidney, blood, nerve, and muscle cells.

Gametes

Reproductive cells involved in sexual reproduction, specifically the egg and sperm.

Interphase

The longest part of the cell cycle (90%) involving normal cellular activity such as protein synthesis and cellular respiration, consisting of $G_1$, $S$, and $G_2$ phases.

$G_0$ (Gap 0)

A phase where a cell is not engaged in the cell cycle and is either performing its cellular duties or at rest, such as mature nerve and heart cells.

Chromatid

One half of a replicated chromosome.

Centromere

The region where sister chromatids are connected and where the spindle fiber attaches during mitosis.

Kinetochore

A protein that attaches to microtubules during the cell division process.

Centrosomes

Structures containing two centrioles that help organize spindle fibers; they are not found in plant and fungi cells.

Prophase

The mitotic phase where the nuclear membrane disintegrates, chromosomes condense (thickening and becoming easily stainable), and centrosomes move to opposite ends to form spindle fibers.

Prometaphase

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

Metaphase

The stage of mitosis where sister chromatids line up along the equator of the cell by actions of the spindle apparatus.

Anaphase

The mitotic stage where centromeres split and sister chromatids are pulled towards their respective poles.

Telophase

The stage where a new nuclear membrane forms around each group of chromosomes and chromosomes uncoil to become less dense.

Cytokinesis

The physical division of the cell into two identical daughter cells; involves a contractile ring in animal cells.

Cyclins

Proteins that control the cell's progress through cellular division by activating Cyclin-dependent kinases ($CDKs$).

Cyclin-dependent kinases ($CDKs$)

Enzymes that work with cyclins by phosphorylating another protein to promote progression of the cell cycle.

$Rb$ (Retinoblastoma)

A negative regulator of the cell cycle that, when active, binds to $E2F$ to prevent DNA synthesis.

Tumor Suppressor genes

Genes that prevent cells from dividing too often.

Proto-oncogenes

Genes that produce proteins encouraging cell division and halting cell death; if mutated, they become oncogenes that permanently turn on cell division.

$$p53$$

Known as the Guardian of the Genome, this tumor suppressor gene on chromosome 17 arrests the cell cycle for DNA repair or triggers apoptosis if damage is irreparable.

Contact Inhibition

A property of normal cells where they stop dividing when they bump against other cells; cancer cells lack this and pile on top of one another.

Metastasis

The process by which malignant tumors shed and spread cancer cells to other parts of the body.

Telomeres

Sections of noncoding, repetitive DNA that act as a protective cap on the tip of each chromosome.

Hutchinson-Gilford progeria

A condition where telomeres are much shorter than normal, shortening the life span of chromosomes.