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Cancers are an example of how important regulation of cell division is, as they arise due to uncontrolled mitosis. Cancer is a group of diseases caused by mutations of the genes that regulate mitosis and the cell cycle. When mitosis is unregulated, uncontrolled cell division occurs, and as a consequence, a group of abnormal cells called a tumour develops. Cancer is a common but potentially deadly disease. Despite this, if diagnosed early it is very much treatable.
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Jetzt kostenlos anmeldenCancers are an example of how important regulation of cell division is, as they arise due to uncontrolled mitosis. Cancer is a group of diseases caused by mutations of the genes that regulate mitosis and the cell cycle. When mitosis is unregulated, uncontrolled cell division occurs, and as a consequence, a group of abnormal cells called a tumour develops. Cancer is a common but potentially deadly disease. Despite this, if diagnosed early it is very much treatable.
Not all tumours are cancerous. Those that are cancerous are called malignant, while those that are non-cancerous are called benign.
Cancers start to form when genes that control cell division experience changes. This is called a mutation. Cell mutations are pretty common and are usually picked up and destroyed by regulatory functions such as early cell death or the body’s immune system. This doesn’t usually cause disturbance to the body, as cells are constantly being replaced. When these cells are not destroyed, the harmful mutation is passed down to all its descendants. This means that many mutated and potentially cancerous cells are formed. This leads to a tumour.
Tumour: an irregular mass of cells.
Fig. 1 - Cancer cells keep on reproducing to form a tumour
Some tumours don’t spread from their original site and don’t cause cancer. Other tumours spread through the body and cause cancer.
The table below shows the different characteristics of benign and malignant tumours.
Table 1. Benign vs malignant tumours.
Benign | Malignant | |
Size | Can grow very large. | Can grow very large. |
Rate of growth | Slow. | Fast. |
Differentiation of cells | Highly differentiated/specialized. | Undifferentiated/ Unspecialized. |
Removal | Typically removed by surgery alone. | Typically, involves surgery, radiotherapy, and chemotherapy. |
Locality | More localized effects on the body. | Often have systemic (whole-body) effects. |
Damage | Less likely to be life-threatening. However, they can obstruct vital organs. | Much more likely to be life-threatening. Typically |
Metastasis | Produce adhesion molecules. These make the tumour cells stick together, so they stay within the tissue they arise from. These are primary tumours. | Do not produce adhesion molecules, so the tumour cells don’t stick together. They tend to spread to other regions of the body through the process known as metastasis. These are known as secondary tumours. |
Capsule | They are surrounded by a capsule of dense tissue, so they remain a compact structure. | Do not have capsules surrounding them. Grow finger-like projections into other tissues. |
Recurrence | Rarely recur after removal. | High rate of recurrence. |
Malignant tumour: tumours that spread through the body and cause cancer.
Benign tumour: a mass of cells that doesn’t invade neighbouring tissue or metastasize.
As you can see in Figure 1, tumours have a different appearance from normal cells.
They have a larger and darker nucleus compared to other cells.
They may have more than one nucleus.
They have an irregular shape.
They don’t produce all proteins needed to function correctly.
They have different antigens on their surface compared to normal cells.
They don’t respond to the body’s regulating processes.
They divide by mitosis more frequently than normal cells.
How does a malignant tumour appear?
Malignant cells develop, divide, and invade normal tissues.
Some of the cells detach and spread through the blood and lymph vessels.
The malignant cells can squeeze through the capillary wall.
They then divide, producing a secondary tumour in a different location to the original tumour. This is called metastasis and it's very dangerous because these secondary tumours are hard to detect and remove.
Metastasis: a piece of a tumour cell breaks off and spreads to another part of the body.
Fig. 2 - Diagram showing how metastasis occurs
There are several genetic factors that increase the likelihood of developing some cancers, but there are also environmental factors. Chemicals and other agents that can cause cancer are called carcinogens. They damage the DNA and cause mutations.
Risk factors: factors that increase the likelihood of developing a disease.
Lifestyle factors that lead to increased risk of cancer include:
Alcohol intake.
Obesity and diet.
Smoking.
Exposure to UV light during either sunbathing or spending time outside.
Viruses spread during sexual intercourse.
There are also things that people may be exposed to at work:
Ionizing radiation.
Chemical carcinogens.
In your exams, you may be asked to evaluate evidence showing correlations between genetic and environmental factors and various forms of cancer.
A correlation is the statistical measure of the relationship between two variables. It is best demonstrated in variables with a linear relationship between each other and can be best visualized using a scatter diagram. When an increase in one variable is accompanied by the increase of another, we say that the two variables a positively correlated. When one variable increases and the other variable decreases, we call it a negative correlation.
Bear in mind that just because there is a correlation between two variables, there isn’t necessarily causation. One variable may not cause changes in the other. Correlation assesses relationships between variables, and these relationships may occur due to different factors.
Correlation coefficient
When sampling data from two variables, we can use a calculation to determine whether the two variables correlate. The variables are plotted on scatter graphs, which indicate possible relationships that we can test. Values will lie between 1 (perfect positive correlation) and -1 (perfect negative correlation).
This is the formula for the correlation coefficient:
x = the values of the first variable.
x̄ = the mean of the values of the first variable.
y = the values of the second variable.
ȳ =the mean of the values of the second variable.
Σ = the sum of.
(x - x̄) = the values of the first variable - the mean of the values of the first variable.
(y - ȳ) = the values of the second variable - the mean of the values of the second variable.
You can lay the data out in a table to work out the equation easily:
Then find the sum of each data column (except columns 3 and 4) and plug them into the equation.
Studies to measure correlation
To ensure correlations are statistically significant and not due to chance, scientists need large amounts of data that they can get using different methods.
In case studies, scientists compare a group of people who have the disease you want to study with a group of individuals who don’t have the disease.
People with disease = Cases
People without disease = Control
The scientists then collect information about risk factors that each group has been exposed to. The participants need to be matched by known risk factors such as gender and age. These factors aren’t investigated in the study but mean that the control group is representative of the case group.
Cohort studies are very time-consuming and expensive in comparison to case studies. This is because it takes people a long time to develop diseases.
Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.
Most types of medicine focus on treating an illness or injury. This means prescribing medicine or giving therapies that treat the illness and hopefully cure the patient. Preventive medicine aims to stop an illness before it starts. It takes a holistic approach by focusing on the many factors that play a role in health. This includes maintaining a healthy lifestyle.
When talking about cancer, we often use the term prevention. Cancer doesn’t have a single cause. Some causes are beyond our control (e.g. genetics, gender, or age) but some factors are within our control. These are called lifestyle factors. Lifestyle factors include:
Diet: there is strong evidence that suggests that a good diet rich in fruit, vegetables, and fibre reduces the risk of getting cancer.
Exercise: people who are more physically active are at a lower risk than those who do little or no exercise.
Sunlight: the more ultraviolet light someone is exposed to, the more at risk they are.
Smoking: both smokers and those who breathe in tobacco passively are at increased risk of cancer.
In a test, your teacher may ask you to evaluate experiments related to any one of these lifestyle factors. A common one is smoking, as there is a lot of evidence that shows that smoking increases the risk of lung cancer.
When tobacco was first introduced to Britain in the sixteenth century, it was seen as a harmful social activity. However, in the late 1940s, after an alarming increase in deaths from lung cancer, doctors began to wonder whether tobacco was the cause of this increase.
Some facts from NHS England include:
A tumour develops due to abnormal cellular growth. In the case of cancer, this cellular growth is uncontrollable and spreads throughout the body.
Malignant and benign tumors.
During cancer the cell cycle is uncontrolled.
Through a process called metastasis.
They can affect a healthy cell’s genetic makeup as well as the body’s immune system. Specific viruses usually affect specific cells in the body, and therefore only certain viruses are linked with certain kinds of cancer.
The statistical measure of the relationship between two variables.
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SIGNUP SIGNUPFlashcards in Tumour39
Start learningWhat is the general appearance of a tumour cell?
They have a larger and darker nucleus compared to other cells.
They may have more than one nucleus.
They have an irregular shape.
They don't produce all proteins needed to function correctly
They have different antigens on their surface compared to normal cells.
They don't respond to the body's regulating processes.
They divide by mitosis more frequently than normal cells.
Metastasis definition
When a piece of tumour cell breaks off and spreads to another part of the body.
What are cohort studies?
Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.
What factors affect the risk of developing cancer?
Correlation definition
A correlation is the statistical measure of the relationship between two variables. It is best demonstrated in variables with a linear relationship between each other.
What are cohort studies?
Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.
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