cancer genetics

Question 1

3 important cancer genes

Answer 1

oncogenes, tumour suppressor genes and DNA repair genes

Question 2

oncogenes explained

Answer 2

cellular on switches that allow cells to grow and divide. One mutation is sufficient for cancer development

Question 3

tumour suppressor genes explained

Answer 3

off switches, prevent growth. Act before DNA synthesis , two copies need to be mutated

Question 4

DNA repair genes explained

Answer 4

rectify damage from various sources such as radiation. acts after DNA synthesis

Question 5

incidence of familial breast cancer in the UK

Answer 5

1/8

Question 6

average age of breast cancer development

Answer 6

61

Question 7

predisposed age of onset

Answer 7

30-50 years old

Question 8

risk of breast cancer if mutation is found

Answer 8

85%

Question 9

main mutations in breast cancer + location

Answer 9

BRCA1- chromosome 17q

BRCA2- chromosome 13q

Question 10

differences between BRCA1 and BRCA2 mutations

Answer 10

BRCA1- cumulative risk greater earlier on, ovarian cancer risk greater after 40

BRCA2- cumulative risk greater later on, greater ovarian cancer risk after age of 50

Question 11

breast screening explained

Answer 11

mammograms, if no BRCA found annual between ages of 40-60

if BRCA found then MRI and mammograms annually from 30-50, then mammograms annually to age 70

Question 12

risk reducing surgery and percentage risks

Answer 12

mastectomy- breast removal- less than 10& risk

ovary removal- less than 2% risk

Question 13

Li Fraumeni syndrome explained

Answer 13

mutations in TP53 cell cycle/ tumour suppressor gene

autosomal dominant condiition with 90% penetrance

causes a variety of cell cancers

Question 14

Two main bowel cancers

Answer 14

Familial adenomatous polyposis FAP and Lynch syndrome

Question 15

explain FAP

Answer 15

severe mutations in APC gene, leading to a predisposition to develop hundreds of bowel polyps

cancer often in early twenties and prophylactic colectomy is recommended

Question 16

Lynch syndrome explained

Answer 16

hereditary non-polyposis colorectal cancer

mutations in MLH1, MSH2, MSH6 PMS2

if many people in family develop bowel cancers, recurrent

Question 17

screening for bowel cancer

Answer 17

colonoscopy, reach the ceacum, every two years for Lynch syndrome, FAP ever year

Question 18

treatments

Answer 18

lasoo the polyps in Lynch syndrome, too many in FAP

Question 19

multiple endocrine neoplasia inheritance

Answer 19

autosomal dominant

Question 20

two types explained

Answer 20

Type 1- all the Ps, pituitary, pancreas and parathyroid tumours, caused by mutations in menin leading to mostly benign tumours

Type 2- caused by mutations in RET, leads to malignant tumours, medulla thyroid cancer, pheochromocytoma and parathyroid tumours

Question 21

Knudson’s two hit hypothesis explained

Answer 21

a cell can initiate a tumour only when it has two mutant alleles, an individual who has inherited a germline mutation in a tumour suppressor gene only requires one somatic mutation, increasing their risk and age of onset

Question 22

2 types of cancer testing defined

Answer 22

predictive- search for genetic mutations linked with a condition before you show symptoms

diagnostic testing- find out a condition associated with symptoms you already have