-To get a sense of the questions that are going to be on the midterm,
go on the library website and access the past exams. The past exams
are most representative of the questions that will be on the
-The genetics of cancers ties together the topics of mutations that we’ve
been talking about for a while.
-There are over one hundred types of cancers in which cells can grow
out of control & destroy healthy tissue. The kinds of things that can
happen are there is a failure to regulate growth, proliferation, and/or cell
death. Cell death is when cells die. Usually, they’ll die if they’ve been
injured in some fashion.
-The overall cause of cancer, from a biological point of view, is
mutations in genes. These mutations can result in some instances in
altered gene expression.
-These are some of the characteristics of a cancer cell.
-Most normal cells will, when you put them in a culture dish, will
divide until they reach the edge of the dish and the dish is completely
full of cells but the cells do not have the ability to grow over one
another. So a normal cell would have this characteristic called contact
inhibition. When the cells are contacting other cells, they stop growing.
That’s absent in cancerous cells where they continue to proliferate even
when they’re touching other cells.
-When you damage normal cells, so say you damage DNA by
irradiating it, it will usually die via cell death. In some instances, the
cancer cells are resistant to radiation – they remain alive even in the
presence of radiation. This isn’t the case for all cancer cells since
radiation is used to treat certain forms of cancer.
-As well, there’s genomic instability. If you look at the karyotype (a
picture of the chromosomes) of a cancerous tumour, you’ll often see
huge changes in the chromosome number, translocations, etc. Part of
the reason is that throughout the cancer process, there’s a defect in
repair. So that can also be part of a cancer process where you end up w/
even more mutations than previously.
-Some cancers are immortal in the sense that in normal cells, you can
grow cells for a certain period of time and then they die whereas certain
cancer cells can continue to grow for many years.
-There are cells used in labs called HeLa cells which came from a
woman w/ cervical cancer in the 40s or 50s and her cells are still being
cultured today in labs. So these cells have become immortal.
-Tumour cells have the ability to break through tissues and basement
membranes and move to other locations. This process is called
metastasizing which is the ability to move to a new place. So they can
go and disrupt local tissues, move through the blood, and move into
different locations. This is only characteristic of some cancers.