How oncogenes arise

Question 1

What are the two main categories of cancer-related genes?

Answer 1

Proto-oncogenes and tumour suppressor genes.

Question 2

What is the normal function of proto-oncogenes?

Answer 2

Stimulate or enhance cell division and viability; inhibit cell death.

Question 3

What are oncogenes?

Answer 3

Mutated or damaged versions of proto-oncogenes that contribute to cancer.

Question 4

What is the function of tumour suppressor genes?

Answer 4

Prevent cell division or promote cell death.

Question 5

How can oncogenes arise inside cells?

Answer 5

Through cancer viruses introducing oncogenes or by mutations converting proto-oncogenes into oncogenes.

Question 6

What are the five mechanisms that can convert proto-oncogenes into oncogenes?

Answer 6

Point mutation, gene amplification, chromosomal translocation, local DNA rearrangement, insertional mutagenesis.

Question 7

Who discovered the first retrovirus linked to cancer?

Answer 7

Peyton Rous.

Question 8

What oncogene is associated with rat sarcoma?

Answer 8

v-ras oncogene.

Question 9

How is the human version of v-ras written?

Answer 9

RAS (gene), Ras (protein).

Question 10

What is a point mutation?

Answer 10

A change in a single nucleotide base that can convert a proto-oncogene into an oncogene.

Question 11

How does point mutation affect the RAS gene?

Answer 11

Changes a single nucleotide, making it an oncogene that causes cancer.

Question 12

What is gene amplification?

Answer 12

Replication of a DNA region many times, leading to dozens or thousands of gene copies.

Question 13

What are HSRs?

Answer 13

Homogeneously staining regions where amplified DNA appears uniformly stained.

Question 14

What are DMs?

Answer 14

Double minutes, small extra-chromosomal DNA fragments containing amplified genes.

Question 15

How do HSRs and DMs differ?

Answer 15

HSRs remain attached to chromosomes, DMs exist independently.

Question 16

What genes are commonly amplified in human cancers?

Answer 16

MYC gene family and ERBB2 gene.

Question 17

What is chromosomal translocation?

Answer 17

When a chromosome piece breaks off and attaches to another chromosome.

Question 18

What chromosome abnormality is common in chronic myelogenous leukemia?

Answer 18

Philadelphia chromosome.

Question 19

Which chromosomes are involved in forming the Philadelphia chromosome?

Answer 19

Chromosomes 9 and 22.

Question 20

What fusion gene is created by the Philadelphia chromosome?

Answer 20

BCR-ABL fusion gene.

Question 21

What is the effect of the BCR-ABL fusion gene?

Answer 21

It produces a protein that contributes to cancer development.

Question 22

What is local DNA rearrangement?

Answer 22

Movement of DNA sequences that disrupts proto-oncogene structure or expression.

Question 23

What are types of local DNA rearrangements?

Answer 23

Deletions, insertions, transpositions, and inversions.

Question 24

Example of fusion gene from DNA inversion?

Answer 24

TRK oncogene from fusion of TPM3 and NTRK1 genes.

Question 25

What is insertional mutagenesis?

Answer 25

A virus inserts near a proto-oncogene and activates it through its LTRs.

Question 26

What are LTRs?

Answer 26

Long terminal repeats that promote transcription of nearby genes.

Question 27

How does insertional mutagenesis lead to cancer?

Answer 27

Overproduction of a normal cellular protein due to activation by viral LTRs.

Question 28

What is the general result of mutations converting proto-oncogenes into oncogenes?

Answer 28

Altered gene structure or expression that promotes cancer.

Question 29

Which mechanism typically results in normal protein overproduction, not abnormal protein?

Answer 29

Gene amplification.

Question 30

Which mechanism typically results in an abnormal protein being produced?

Answer 30

Point mutation.