8.2.3 Gene expression and cancer Flashcards
What is cancer?
Cancer is a group of diseases caused by damage to the genes that regulate mitosis and the cell cycle.
What are malignant tumours?
Malignant tumours are cancerous tumours.
What are benign tumours?
Benign tumours are non-cancerous tumours.
What are the characteristics of benign tumours?
Benign tumours have slow growth, defined boundaries, retain function and normal shape, do not spread easily, and are easy to treat.
What are the characteristics of malignant tumours?
Malignant tumours have rapid, uncontrollable growth, undefined boundaries, cells that do not retain function, spread quickly, and are difficult to treat.
From what are cancer cells derived?
Cancer cells are derived from a single mutant cell.
What does a single mutant cell cause?
It causes uncontrolled cell division and uncontrolled mitosis in the cell.
What are the two main types of genes that play a role in cancer?
Tumour suppressor genes and oncogenes.
What are oncogenes?
Oncogenes are mutations of proto-oncogenes.
What do proto-oncogenes do?
stimulate a cell to divide when growth factor attach to protein receptor on cell surface membrane
activates genes that cause DNA to replicate
cell divides
can become permanently activated (switched on)
What happens if a proto-oncogene mutates to an oncogene?
It can become permanently activated (switched on).
Why can oncogenes become permanently activated?
1 - Receptor protein on cell surface membrane can be permanently activated, causing cell division even in the absence of growth factors. 2 - Oncogene may code for a growth factor produced in excessive amounts, leading to excessive cell division.
cell division too rapid and out of control - tumour
What do oncogenes lead to?
Oncogenes lead to cell division being too rapid and out of control, resulting in tumours.
How can some cancers be caused?
By inherited mutations of proto-oncogenes
cause the oncogens to be activated
tumour suppressor genes
Tumour suppressor genes slow down cell division, repair mistakes in DNA, and tell cells when to die (apoptosis)- (programmed cell death)
what do tumour supressor genes do
maintain a normal rate of cell division
prevent formation of tumours
What happens if a tumour suppressor gene becomes mutated?
It becomes inactive (switched off).
What happens if a tumour suppressor gene becomes inactive?
It stops inhibiting cell division, causing cells to grow out of control.
How does the inactivation of tumour suppressor genes cause tumours?
Mutated cells can clone themselves, making tumours.
What is the difference between oncogenes and tumour suppressor genes?
Oncogenes cause cancer as a result of the activation of proto-oncogenes, while tumour suppressor genes cause cancer when inactivated.
What is abnormal DNA methylation?
common in developing tumours and involves increased methylation.
What is hypermethylation?
increased methylation.
Describe the process of hypermethylation leading to cancer.
- occurs in specific region (promoter region) of tumour supressor genes
- Becomes inactivated
- transcription of promoter region of TSG inhibited
- TSG switched off
- Increased cell division
- forms tumours
Reduced methylation
hypomethlylation- in oncogenes - forms tumours
What is hypomethylation?
Hypomethylation refers to reduced methylation in oncogenes, which can form tumours.
What causes an increase in breast cancer?
An increase in oestrogen concentration.
How can oestrogen cause tumour development?
Oestrogen activates a gene that promotes transcription. If this gene controls cell division and growth, it will be continuously activated, leading to uncontrolled cell division and tumour formation. Oestrogen can also cause proto-oncogenes in breast tissue to become oncogenes, leading to breast cancer
What is the link between oestrogen and breast cancer?
High concentrations of oestrogen in adipose tissue can over-activate cell division, leading to uncontrolled growth.
How does a benign tumour differ from a malignant tumour (1)
Benign tumours do not invade tissues or spread (metastasize).
How can tumours harm the body? (2)
Tumours can damage organs and cause blockages or pressure on organs.
Explain the link between sunbathing and skin cancer.
UV radiation causes mutations in genes controlling cell division.
Why are fair-skinned people more at risk for skin cancer?
They have less melanin, providing less protection from UV.
Why does a family history increase cancer risk? (1)
There may be an inheritance of oncogenes or predisposition genes.
How can a tumour suppressor gene mutation cause tumours? (1)
The gene becomes inactivated, leading to uncontrolled cell division.
Why do some mutations not change the amino acid sequence? (1)
The genetic code is degenerate; mutations may occur in non-coding DNA.
How do monoclonal antibodies stop tumour growth? (3)
The antibody binds to the receptor, preventing growth factor binding and stopping cell division stimulation.
How does methylation of tumour suppressor genes lead to cancer? (3)
It prevents transcription, resulting in no protein to prevent division and uncontrolled mitosis.
Define epigenetics. (2)
heritable gene function changes without changes in the DNA sequence.
Which control factors bind DNA/protein?
Oestrogen binds protein; Methyl binds DNA; Acetyl binds protein.
How does increased methylation lead to cancer? (3)
Increased methylation silences tumour suppressor genes, preventing transcription and leading to uncontrolled cell division.
How do benign and malignant tumours differ? (1)
Benign tumours do not metastasize or invade other tissues.
How do tumour suppressor gene alterations lead to tumours? (2)
Methylation or mutation prevents gene transcription, leading to no control of mitosis and uncontrolled division.
How does an activated oestrogen receptor affect target cells? (2)
It binds to DNA and promotes transcription.
Why does oestrogen only affect target cells? (1)
Only target cells have complementary receptors.
How does endoxifen reduce breast tumour growth? (2)
Competes with oestrogen; Blocks receptor activation.
Why does an antibody bind to a transcription factor? (2)
The antibody has a complementary shape, forming an antigen-antibody complex.
What is a genome? (1)
complete set of an organism’s DNA.
What is a malignant tumour? (3)
A malignant tumour invades tissues, metastasizes, and causes damage.
Why does the death rate from malignant skin tumours increase with age?
There is longer UV exposure leading to more mutations.
Why does skin colour affect skin cancer death rate? (2)
Darker skin has more melanin, providing more UV protection.
