Causes of Cancer
What is cancer?
A group of diseases in which cells grow and divide uncontrollably due to mutations in genes that regulate the cell cycle.
What do we call a group of cancerous cells?
A tumor.
Why do we not want cell division to happen all the time?
Uncontrolled division can lead to tumors and cancer and disrupt normal tissue function.
Name 2 reasons why cells can form tumors.
Mutations in proto-oncogenes and/or tumor suppressor genes; failure of apoptosis; exposure to carcinogens (any two).
Why is the option of surgery limited?
It is only effective if the tumor is localized and has not spread (metastasized).
What do all types of cancer have in common?
All cancers involve uncontrolled cell division caused by genetic mutations.
What is apoptosis and why would it occur?
Apoptosis is programmed cell death; it occurs when a cell is damaged, infected, or no longer needed.
What keeps normal cells from dividing frequently?
Cell cycle checkpoints, regulatory proteins (like cyclins), and signals from the environment.
What is a carcinogen? Give one example.
A carcinogen is a substance or exposure that can cause cancer (e.g., UV radiation, tobacco smoke).
What is chemotherapy?
A treatment that uses drugs to kill rapidly dividing cells.
Explain how cancer-causing mutations to genes are like the accelerators and brakes of a car.
Some genes act like accelerators (promote cell division), while other genes act like brakes (slow/stop division). Cancer occurs when accelerators are stuck “on” and/or brakes fail.
What is contact inhibition and how does it differ in normal cells vs. cancer cells?
Contact inhibition is when cells stop dividing once they touch neighboring cells. Normal cells exhibit this; cancer cells ignore it and continue dividing.
What occurs at the first cell cycle checkpoint?
(G1 checkpoint) The cell checks for size, nutrients, and DNA damage before DNA replication.
What is the difference between passenger and driver mutations?
Driver mutations contribute to cancer progression; passenger mutations do not affect cancer growth.
How does chemotherapy work?
It targets and disrupts the cell division process, especially in fast-dividing cells like cancer cells.
What are the genes called whose normal function is to stop cell division?
Tumor suppressor genes.
Explain how telomerase affects cancer cells.
Telomerase maintains telomere length, allowing cancer cells to divide indefinitely instead of aging and dying.
What occurs at the second cell cycle checkpoint?
(G2 checkpoint) The cell checks that DNA has been properly replicated and is undamaged.
What is angiogenesis and how does it affect cancer cells?
Angiogenesis is the formation of new blood vessels; tumors use it to obtain oxygen and nutrients, allowing them to grow.
What is the main concern with using chemotherapy as a cancer treatment?
It also harms healthy fast-dividing cells (e.g., hair, digestive lining), causing side effects.
What are the genes called whose normal function is to promote cell division?
Proto-oncogenes.
Why does risk of cancer increase significantly with age?
Because mutations accumulate over time, increasing the likelihood of multiple mutations needed for cancer.
What occurs at the third cell cycle checkpoint?
(M checkpoint) The cell ensures chromosomes are properly attached to spindle fibers before separation.
How many alleles are required to be mutated to cause cancer in proto-oncogenes vs. tumor suppressor genes?
Proto-oncogenes: 1 mutated allele
Tumor suppressor genes: 2 mutated alleles
What is the spread of cancer cells from the original tumor to other parts of the body called?
Metastasis