Week 14 When Things "Go Bump in the Night for the Cell"

What is a mutation?

A heritable change in the genetic material.

Why are mutations essential?

They are essential to the continuity of life and serve as a source of variation for natural selection.

What role do DNA repair systems play?

They reverse DNA damage to maintain genetic integrity.

What is Xeroderma pigmentosum (XP)?

A genetic disorder caused by mutations that affect DNA repair mechanisms.

What are point mutations?

Mutations that involve a base substitution or the addition or deletion of a single base pair.

What is a silent mutation?

A base substitution that causes no change in the amino acid sequence of a protein.

What is a missense mutation?

A base substitution that changes one amino acid in the polypeptide chain.

What is a nonsense mutation?

A base substitution that changes a normal codon to a stop codon, shortening the polypeptide.

What is a frameshift mutation?

A mutation caused by the addition or deletion of a base pair, altering the reading frame of the gene.

What are mutagens?

Chemical or physical agents that alter DNA and increase the mutation rate.

What are chemical mutagens?

Agents that disrupt base-pairing or replication, modifying nucleotide structures.

What is the effect of ionizing radiation?

It creates free radicals that can cause deletions or breaks in DNA strands.

What is direct DNA repair?

A repair enzyme recognizes and directly restores an incorrect structure in DNA.

What is base excision repair?

A repair process where an abnormal base is removed and replaced using the complementary DNA strand as a template.

What is methyl-directed mismatch repair?

A repair process that corrects base-pair mismatches in DNA.

What are oncogenes?

Genes that, when mutated, become overactive and contribute to uncontrolled cell growth.

What role do growth factors play in cell division?

They are hormones that bind to cell surfaces, initiating a cascade that activates specific genes to promote cell division.

What is a proto-oncogene?

A normal gene that can become an oncogene if mutated.

What are the four common genetic changes that can lead to oncogenes?

1. Missense mutations 2. Gene amplifications 3. Chromosomal translocations 4. Retroviral insertions

What are the typical functions of tumor-suppressor genes?

They maintain genome integrity, check DNA damage, inhibit cell division, and prevent abnormal cell growth.

What are checkpoint proteins?

Proteins that monitor the integrity of the genome and prevent a cell from progressing through the cell cycle if damage is detected.

What are Barr bodies?

Inactivated X chromosomes in female mammals, which ensure dosage compensation of X-linked genes.