Chapter 15: Mutations and Cancer

Vocabulary review flashcards covering Chapter 15 study notes on types of mutations, tumor development, oncogenes, and tumor suppressor genes.

Mutation

A permanent, heritable change in the DNA sequence that is passed to daughter cells when a cell divides, as opposed to DNA damage that is corrected by repair mechanisms before division.

Point Mutation

A mutation that occurs when one base is substituted for a different base, causing a base pair to change (such as an A-T base pair changing to a G-C base pair).

Silent Mutation

A mutation that changes the codon sequence in the DNA/mRNA but does not change the amino acid sequence, usually having no effect on the structure or function of the resulting protein.

Missense Mutation

A mutation that changes the codon sequence to specify a different amino acid, typically having a neutral or negative effect on protein function depending on the chemical nature and location of the alteration.

Nonsense Mutation

A mutation that changes an amino acid-specifying codon into a STOP codon, causing translation to terminate prematurely and producing a shortened, nonfunctional or negatively affected protein missing terminal amino acids.

Frameshift Mutation

A mutation caused by the addition or deletion of a number of nucleotides not divisible by $3$, shifting the reading frame and resulting in completely altered codons and amino acid sequences downstream of the site.

In-Frame Addition or Deletion

The addition or deletion of a number of nucleotides divisible by $3$ from a gene, which adds or removes amino acids from the polypeptide without altering the reading frame of downstream codons.

Germ-Line Cell

A gamete-producing cell (giving rise to egg or sperm cells); mutations occurring in these cells are heritable and can be transmitted to offspring.

Somatic Cell

Any body cell that is not a germ-line cell; mutations occurring in somatic cells cannot be passed on to offspring because offspring only inherit DNA through gametes.

Spontaneous Mutation

A mutation that occurs naturally without external intervention, such as an uncorrected error made during DNA replication by DNA polymerase.

Induced Mutation

A mutation caused by an environmental agent, which can be a chemical agent (such as chemicals found in cigarette smoke) or a physical agent (such as UV radiation or high-energy ionizing radiation).

Cancer

A disease state caused by the accumulation of mutations that lead to uncontrolled cell proliferation (division).

Benign Tumor

An overgrowth of non-cancerous cells that exhibit an increased rate of cell division but remain under normal regulatory mechanisms and cannot invade surrounding tissues.

Malignant Tumor

An overgrowth of cancerous cells that have escaped normal regulatory controls, allowing them to proliferate uncontrollably and invade neighboring tissues.

Metastasis

The process whereby malignant or cancerous cells enter body fluids (the bloodstream and/or lymphatic vessels) and travel to establish secondary growths in other locations of the body.

Apoptosis

Programmed cell death that occurs when a cell risks causing harm to the organism (e.g., irreparable DNA damage, viral infection), during embryonic development to sculpt tissues, or to eliminate worn-out cells.

Proto-Oncogene

A normal gene encoding proteins that promote cell division or prevent apoptosis, which promotes cancer development when it acquires a gain-of-function mutation that renders its product overactive.

Oncogene

A mutated proto-oncogene that has acquired a gain-of-function mutation, resulting in an overactive protein that drives abnormally high rates of cell division or blocks necessary apoptosis.

Tumor Suppressor Gene

A gene that promotes cancer development only when it sustains a loss-of-function mutation; normal products inhibit cell division, promote apoptosis in damaged cells, or perform DNA repair.

myc Gene

A proto-oncogene encoding a protein that switches on genes promoting cell division; acquiring a gain-of-function mutation promotes cancer development.

twist Gene

A proto-oncogene encoding a protein that prevents cells from undergoing apoptosis; acquiring a gain-of-function mutation promotes cancer by inappropriately keeping damaged cells alive.

APC Gene

A tumor suppressor gene encoding a protein that inhibits or prevents cell division; acquiring a loss-of-function mutation promotes cancer by removing controls on cell proliferation.

BAX Gene

A tumor suppressor gene encoding a protein that promotes apoptosis; acquiring a loss-of-function mutation promotes cancer because damaged cells are no longer triggered to die.