BIO171 Exam 2

what is cancer?

a disease in which cells divide uncontrollably and spread to other parts of the body

tumor

mass of cells that divide uncontrollably

benign tumor

cells do not spread

malignant tumor

cells spread to new sites (cancerous)

metastasis

spreading of tumor to new site

explain why tumor cells grow uncontrollably

the genes that control cell division are mutated in cancer cells (they don’t stop dividing when they’re supposed to)

what are the three types of genes that, if mutated, can result in tumors?

proto-oncogenes; tumor suppressor genes; DNA repair genes

what happens if proto-oncogenes are mutated?

turns into an oncogene + becomes a hyperctive protein, which stimulates uncontrollable cell division

what happens if tumor suppressor genes are mutated?

the protein becomes inactive and doesn’t prevent cell division, causing uncontrollable cell division

what happens if DNA repair genes are mutated?

damaged genes aren’t repaired, causing a lack of control of cell division if either of the other genes has a mutation

what are the three major causes of mutations leading to cancer, and what percentage of cancer mutations are attributable to each?

inherited - 10%

mistakes in DNA replication - 67%

environmental - 29%

what is a risk factor?

something that increases the chance of developing a disease

which risk factors are beyond our control?

family history & age

which risk factors are under our control?

lifestyle, viral infections, & chemicals/pollutants

what are the top seven avoidable risk factors and what percentage of cancer cases are attributable to each?

tobacco smoking 19%

excess body weight 7%

alcohol 6%

ultraviolet radiation 5%

poor diet 4-5%

infections 3-4%

physical inactivty 3%

suppose you find out that researchers have established that a particular substance (e.g., cigarette smoke) increases the risk of a particular type of cancer (e.g., lung cancer). Are experiments with humans likely to have contributed to this conclusion? Why or why not?

no, because it wouldn’t be ethical to use experimental tests on humans that could give them a serious disease like cancer

suppose we find an association between two variables. Explain why we cannot conclude from that association that the two variables are causally related

we cannot conclude causation because there could still be some other variable not known or included in tests that is the real causal agent. We can only rule out alternative explanations without definitively associating our variables with one another

what is a non-experimental test, and why are experiments better than non-experimental tests for establishing cause and effect?

non-experimental test→ a test where researchers aren’t manipulating the variables of interest

experiments are better for establishing cause and effect because they allow researchers to manipulate the independent variable while controlling other factors, which isolates its impact on a dependent variable and establishes a clear, testable relationship. with non-experimental tests, any observed relationship could be due to a third confounding variable or reverse causality (DV occurs before IV)

how do statistical models help us determine risk factors?

by accounting for the effects of variables associated with the factor of interest

if the factor of interest is still associated with the cancer risk, but we’ve ruled out the other explanations, then this increases the likelihood that that factor is a risk factor