3)Cancer Flashcards
G1/M is an important checkpoint in the cell cycle. State the four conditions that must be met to allow cells to progress through the G1/M checkpoint.
- Check cell has grown to the required size
- Check there are enough growth factors
- Check enough nutrients are available
- Check that damage to DNA has not occurred
Using the cell cycle in your answer, explain how DNA mutations may give rise to uncontrolled cell growth.
Tumor suppressor genes control the passage of cells through the cell cycle check point. Mutations in TSG means that cells are no longer subjects to checks and my be able to pass through more quickly without meeting regulations.
Proto-oncogenes help to drive the cells through the cell cycle in times of growth and division. Mutation in proto-oncogenes continuously switches on the protein. It is then known as an oncogene and will drive cells to continuously through the cell cycle leading to unregulated division.
Name four factors that are responsible for DNA mutations: list them as 1) exogenous (external or environmental) and 2) endogenous (internal).
Exogenous- UV radiation (UVA & UVB), PAH
Endogenous- ROS (reactive oxygen species), internal DNA errors during replication.
Explain how a virus can cause cancer, using a specific example of a virus and a cancer.
Some viruses insert their DNA into other host cell DNA. In humans an example would be HPV strains specifically HPV16 & HPV18. If this inserts into the tumor suppressant gene P53, then P53 will have incorrect DNA sequence, leading to the non- functional P53 protein, which means it can no longer repair the damaged cell.
Explain the difference between a cancer cell and a normal cell
The growth of a cancer cell is uncontrolled (0.5) whereas the growth of a non-cancerous cell is strictly regulated by checkpoints of the cell cycle (0.5).
Cancer cells are able to divide indefinitely (they are immortal) (0.5) whereas non-cancerous cells have a set number of divisions they are able to go through before they will go through programmed cell death (0.5).
Cancer cells appear disorganised/lose usual features (0.5); non-cancerous cells remain organised and maintain usual features (0.5)
Cancer cells can metastasize by a process of invasion of blood and/or lymphatic vessels (0.5); non-cancer cells do not invade nearby tissues (0.5)
Explain how cancer staging is used to differentiate between cancers at stage I, II, III and IV.
Stage I: Localised (not yet invaded surrounding tissue
Stage II: Early signs of invasion into nearby tissue
Stage III: Later more advanced signs of invasion into nearby tissue
Stage IV: Even further advanced invasion, through the tissues to invade the bloodstream or lymph
Give a specific named example of a) a common oncogene and b) a tumour suppressor gene involved in cancer and for a) and b) explain how they can cause cancer to develop.
a) Common oncogene: RAS/AKT/MYC (0.5). The oncogene is a signalling molecule which usually drives cells forward through the cell cycle (0.5) but it has a mutation (0.5) that makes it continuously switched on (0.5), so it drives cells through the cell cycle faster than normal (0.5), leading to uncontrolled cell growth and cancer can result.
b) Common tumour suppressor gene: Rb or P53 (0.5). The tumour suppressor usually inhibits (0.5) passage through stages of the cell cycle if they have DNA damage/insufficient nutrients (0.5); without this checkpoint, cells can still proceed through the cell cycle with damaged DNA or in inadequate growth conditions (0.5).
Explain how cancer grading could be used to determine the stage of cancer development.
Grading is carried out under a microscope (0.5) and is used to detect cancer cells by looking at their individual features. If the cells are disorganised (0.5) or de-differentiated (0.5), it is a possible sign of cancer, which will be called dysplasia (0.5) in the early stages (0.5). If the disorganisation or de-differentiation is more advanced (0.5), this is a sign of a later stage of cancer development (0.5), where cells could be invasive/metastatic (0.5).
State four differences between a malignant and a benign tumour.
A malignant tumour grows quickly (0.5) whereas a benign tumour grows slowly (0.5)
A malignant tumour often invades surrounding tissue (0.5) whereas a benign tumour does not invade surrounding tissue (0.5)
A malignant tumour has irregular borders (0.5); a benign tumour has distinct borders (0.5)
A malignant tumour may spread to other parts of the body by metastasis (0.5); a benign tumour does not have invasive cells, so it will not be able to spread through tissue to reach the bloodstream and metastasize (0.5).
State four common signs or symptoms of cancer.
Headaches
Pain,
Fatigue
Weight loss,
