genetics 3: gene mutations

Question 1

what mutation results in loss of APC gene?

Answer 1

deletion in 5q21

Question 2

what is the APC tumour suppression gene involved in?

Answer 2

cell adhesion & signalling

• participates in WNT signalling pathway
• negatvie regulator of βcatenin -> prevents uncrontrolled cell division

Question 3

what does loss of the APC gene cause?

Answer 3

90% risk of developing colorectal carcinoma

- sufferers develop multiple benign adenomatous polyps of the colon

Question 4

outline some differences between oncogenes vs tumour suppressor genes:

Answer 4

gene active in tumour vs inactive
specific translocations / point mutations vs deletions / mutations
mutations rarely hereditory vs can be inherited
dominant at cell level vs recessive at cell level
broad tissue specificity vs considerable tumour specificity
leukaemia & lymphoma vs solid tumours

Question 5

outline the pathway of development of colorectal cancer:

Answer 5

normal epithelium
+ APC -> hyperproliferative epithelium
+ K-ras + dna hypomethylation -> adenoma
+ p53 -> carcinoma -> metastasis