Cancer Genetics

Question 1

What is cancer

Answer 1

All cancers are genetic diseases and changes in the DNA sequence of key genes which are known as cancer genes cause this abnormal division of the cells .

DNA polymerase can also make mistakes , changes can also occur due to exposure to mutagens such as UV

Question 2

What causes cancer

Answer 2

Chemicals ( e.g. from smoking) and radiation can damage genes ( environment)

Viruses can introduce their own genes into cells ( exogenous factors)

By heredity , alteration in genes that make a person more susceptible to cancer can be passed to the next generation ( genetics - rate and common)

Meat cooked at high temps can also lead to an increased risk of cholesterol, pancreatic and prostate cancer

Question 3

What is a benign tumour

Answer 3

Massive well differentiated cells that grow slowly and is capsulated and lack the ability to invade neighbouring tissues or to metastasise

Question 4

What is a malignant tumour

Answer 4

Not limited in its growth and the cells are poorly differentiated and capable of dividing into adjacent issues and maybe capable of spreading distant issues at a microscopic level if there are new bed vessels it may be categorised as malignant

Question 5

What do cancer cells look like

Answer 5

Large number of dividing cells
Large, variably shaped nuclei
Large nucleus to cytoplasm ratio
Variation in size and shape 
Loss of normal cell features
Disorganised arrangement 
Poorly defined tumour boundary

Question 6

Microscopic appearance of cancer cells

Answer 6

Pronounced irregular microscopic membrane and there are increased activity of nucleoporins which causes an increase in the input of transcriptional factor

Question 7

Carcinoma

Answer 7

Rise from epithelial cells - most common are lung, breast and colon

Question 8

Sarcoma

Answer 8

Elle found in the supportive cells of the body . Bone, cartilage, fat connective tissue and muscle

Question 9

Lymphomas

Answer 9

Cancers that arise in the lymph nodes and tissues of the body’s immune system

Question 10

Leukemia

Answer 10

Cancers of cells that grow in the bone marrow and accumulate in the bloodstream

Question 11

Cancers affecting children

Answer 11

Leukaemia s ( ALL) and in tissues which are undergoing a high rate of proliferation such as brain and testicular cancer

Question 12

6 hallmarks of cancer

Answer 12

Self sufficiency in growth signals
Evading apoptosis 
Insensitivity to anti growth signals
Sustained angiogenesis 
Tissue invasion and metastasis 
Limitless replication potential 

( also deregulated metabolism and avoid immune destruction has been added)

Question 13

The life time risk of developing cancer is a particular tissue is correlated with how often stem cells in the tissue divide

Answer 13

So intestine has high cell proliferation rate and so increased risk of cancer

Question 14

Germ.one mutations

Answer 14

Present in egg or sperm cell
Are heritable ( family syndrome)
Rare
Germ line cells are the only cells that can undergo mitosis and meiosis

Question 15

Somatic mutations

Answer 15

Occur in non germ line tissues
Are non heritable
Very common ( 90% of all cancers)

Question 16

Diff types of mutations in cancer cells

Answer 16

Deletions
Duplications 
Inversions 
Translocations
Single base substitutions ( point mutations- silent, nonsense and missense ) 
Chromosomal instability 
Aneuploidy

Question 17

Multi step carcinogens is with tumour cells as an example

Answer 17

1) initiation where thee is irreversible genetic mutations and allows excessive cell prolif . Colon cancer starts with defect in tumour suppressor gene ( APC)

Then more mutations occur in DNA repair genes or other tumour suppressor genes ( p53) and other growth related genes ( K-Ras)

2) tumour becomes cancerous
3) over time accumulated damage can yield a highly malignant , metastatic tumour

Question 18

Example of distinct somatic mutations

Answer 18

Some cancers have distinct somatic mutations ( C>T) . The DNA damage from UV radiation leads to the formation of covalent bonds between two adjacent pyrimidines ( C and T) in the DNA molecule

Or in smokers - G to T transition

Question 19

Passenger mutations

Answer 19

Many mutations can be tolerated by somatic cells and have no effect but may be in the same genome where a driver mutation is located ( known as hatch hiking)

Question 20

Driver mutation

Answer 20

Leads to clinal expansion - may be in p53 and tumour suppressor

Question 21

Passenger vs driver mutation

Answer 21

Driver mutation will have greater effect on protein function than passenger mutation
And will have more frequent mutations than background mutation rate in a gene
But hard to determine as there is so much variation

Question 22

Oncogenes

Answer 22

Gene that has the potential to cause cancer and it regulates cell proliferation, differentiation and and apoptosis , one mutations is sufficient for role in cancer development ( dominant / gain of function )

Question 23

What is a tumour suppressor gene

Answer 23

Regulates cell during cell division and mutation - might be more important in progression of cancers than the proto oncogenes ( recessive/ loss of function )