Chapter 15

Question 1

What is a mutation?

Answer 1

Heritable change in DNA sequence; can cause variation, disease, or cancer

Mutations are fundamental to genetic diversity and evolution.

Question 2

Define point mutation.

Answer 2

Change in a single base pair (substitution, insertion, or deletion)

Point mutations can lead to various effects on protein function.

Question 3

What is a silent mutation?

Answer 3

Base change does not alter amino acid; no effect on protein

Silent mutations often occur in non-coding regions or result in synonymous codons.

Question 4

Define missense mutation.

Answer 4

Base change substitutes a different amino acid; effect depends on location (e.g., sickle cell)

Missense mutations can lead to altered protein function or stability.

Question 5

What is a nonsense mutation?

Answer 5

Base change produces a stop codon → early termination → nonfunctional protein

Nonsense mutations can severely impact protein synthesis.

Question 6

Define frameshift mutation.

Answer 6

Insertion or deletion (not multiple of 3) shifts reading frame; major change in amino acids

Frameshift mutations often result in completely different proteins.

Question 7

What is a germ-line mutation?

Answer 7

Occurs in gamete-producing cells; inherited by offspring

Germ-line mutations can affect future generations.

Question 8

Define somatic mutation.

Answer 8

Occurs in body cells; not passed to offspring

Somatic mutations can lead to cancer in the individual but are not hereditary.

Question 9

What is a spontaneous mutation?

Answer 9

Natural replication or repair error; rare due to polymerase proofreading

Spontaneous mutations occur without external influence.

Question 10

Define induced mutation.

Answer 10

Caused by external mutagens (chemical or physical)

Induced mutations can result from environmental factors.

Question 11

What is a mutagen?

Answer 11

Agent that causes mutations

Mutagens can be chemicals, radiation, or biological agents.

Question 12

Define chemical mutagen.

Answer 12

Alters nucleotide structure or interferes with DNA replication

Chemical mutagens can lead to various types of mutations.

Question 13

What is a physical mutagen – ionizing?

Answer 13

X-rays/gamma rays; cause DNA breaks or deletions

Ionizing radiation is highly damaging to DNA.

Question 14

Define physical mutagen – nonionizing.

Answer 14

UV light; causes thymine dimers that distort DNA

Nonionizing radiation can lead to skin cancer.

Question 15

What is DNA repair?

Answer 15

Maintains genome stability by detecting and fixing DNA damage

DNA repair mechanisms are crucial for preventing mutations.

Question 16

What are the two events of DNA repair?

Answer 16

(1) Detect DNA irregularity; (2) Repair abnormality

These steps ensure the integrity of the genetic material.

Question 17

Define proto-oncogene.

Answer 17

Normal gene controlling regulated cell growth/division

Proto-oncogenes are essential for normal cellular function.

Question 18

What is an oncogene?

Answer 18

Mutated or overactive proto-oncogene → uncontrolled cell division → cancer

Oncogenes drive the progression of cancer.

Question 19

Define tumor suppressor gene.

Answer 19

Prevents uncontrolled cell growth or triggers apoptosis; mutation causes cancer risk. Examples: p53, BRCA1, RB1

Tumor suppressor genes play a critical role in maintaining cellular homeostasis.

Question 20

What is a cancer overview?

Answer 20

Develops from multiple mutations; benign = localized, malignant = invasive; apoptosis failure = cancer

Cancer is a complex disease resulting from genetic alterations.