when signalling goes wrong

Question 1

tumour suppressor genes and proto-oncogenes

Answer 1

key regulators of cellular processes such as growth, division and apoptosis
mutations can disrupt normal cellular functions and contribute to carcinogenesis

Question 2

tumour suppressor genes

Answer 2

inhibit cell division
promote apoptosis
maintain genomic stability

Question 3

mutated tumour suppressor genes

Answer 3

uncontrolled cell growth and cancer

Question 4

loss of function mutations

mutations in tumour suppressor genes

Answer 4

follow the ‘two-hit hypothesis’
both alleles of the gene must be inactivated for a tumour-promoting effect
can occur through point mutations, deletions or epigenetic silencing

Question 5

TP53

mutations in tumour suppressor genes

Answer 5

regulates cell cycle arrest, DNA repair and apoptosis
loss of function prevents damaged cells from undergoing apoptosis leading to the survival and accumulation of mutations which contribute to cancer progression

Question 6

RB1

mutations in tumour suppressor genes

Answer 6

encodes the retinoblastoma protein which regulates the cell cycle by preventing progression from the G1 to the S phase
when mutated cells can continuously progress through the cell cycle leading to uncontrolled proliferation

Question 7

proto-oncogenes

Answer 7

regulate cell growth and division

Question 8

oncogenes

Answer 8

excessive cellular proliferation and transformation into cancerous cells

Question 9

gain of function mutations

mutations in proto-oncogenes

Answer 9

gene product is overactive, overexpressed, or present inappropriately
drive uncontrolled cell division

Question 10

RAS

mutations in proto-oncogenes

Answer 10

regulate cell growth and survival
mutation results in a constitutively active form of the protein which leads to persisten stimulation of downstream signalling pathways (MAPK) and drives uncontrolled cell proliferation

Question 11

oncogenic viruses

Answer 11

promote cancer by introducing genetic changes into host cells that drive cellular transformation leading to uncontrolled cell growth and tumour formation

Question 12

HPV (human papillomavirus)

oncogenic viruses

Answer 12

a DNA virus that integrates its DNA into the host genome which can cause mutations or alter gene expression of genes involved in cell cycle regulation, apoptosis and DNA repair.
produced E6 and E7 proteins that inactivate key tumour suppressors like p53 and Rb leading to cell cycle dysregulation and resistance to apoptosis

Question 13

vibrio cholerae

bacterial toxins

Answer 13

alters the activity of heterotrimetic G proteins by producing the cholera toxin which disrupts the normal functioning of G-protein coupled receptos signalling pathways.
The A subunit of the cholera toxin catalyses ADP-ribosylation of the G⍺s subunit in the G-protein of host cells.

Question 14

bordetella pertussis

bacterial toxins

Answer 14

alters the activity of heterotrimetic G proteins by producing the pertussis toxin which interderes with the normal signalling of G-protein coupled receptos to disrupt cellular functions and contribures to the symptoms of whooping cough
The pertussis toxin which ADP-ribosylates the G⍺i subunit in the G-protein of host cells.