7.4 Proto-oncogenes and Tumor Supressors

Question 1

What are proto-oncogenes?

Answer 1

genes that encode for transcription factors that stimulate the cell cycle or increase expression of genes that stimulate cell division or growth

Question 2

What are proto-oncogenes critical for?

Answer 2

normal cellular growth and division

Question 3

When is the expression of proto-oncogenes repressed?

Answer 3

when cells are quiescent

Question 4

What occurs to proto-oncogenes in cancer cells?

Answer 4

become altered so they no longer respond to their regulation signals

Question 5

How are proto-oncogenes normally mutated?

Answer 5

cause overexpression or ill-timed expression of proteins needed for cell growth and division

Question 6

When are proto-oncogenes in a permenantly on state?

Answer 6

in cancer cells

Question 7

What are oncogenes?

Answer 7

proto-oncogenes that contribute to a cancer phenotype

Question 8

How many proto-oncogene alleles need to be expressed wrongly to cause cancer?

Answer 8

only one

Question 9

Are oncogenes dominant or recessive?

Answer 9

dominant

Question 10

What are tumor-suppresor genes?

Answer 10

genes that make products that either help to control the regulation of the cell cycle checkpoints ot are involved in the initiation of apoptosis

Question 11

What happens to tumor suppressor genes that are mutated?

Answer 11

cells are unable to respond normally to the checkpoints or are unable to undergo apoptosis

Question 12

How many tumor suppressor alleles need to be mutated to cause cancer?

Answer 12

both alleles

Question 13

Are cancerous tumor suppressor genes dominant or recessive?

Answer 13

recessive

Question 14

What family of genes are the most commonly mutated genes in human cancers?

Answer 14

ras gene family

Question 15

What percentage of tumors have mutations in the ras gene family?

Answer 15

30%

Question 16

What is the function of ras genes?

Answer 16

function at the beginning of signaling cascades that respond to growth factors will stimulate the nucleus to activate transcription factors that induce cell division

Question 17

What do RAS proteins interact with?

Answer 17

GDP-GTP nucleotide exchange factor

Question 18

What happens when a growth factor bings to the RAS protein at the beginning of a signaling cascae?

Answer 18

GDP-GTP factor prompts RAS to lose GDP and gain GTP that will activate a phosphorlyation signaling cascade

Question 19

What do mutations in the ras gene family cause?

Answer 19

prevent the hydrolysis of RAS protein to GDP so it never actually turns off. signal cascade is ALWAYS on

Question 20

What is the most common mutation in human cancers?

Answer 20

TP53 gene