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Lecture

Topic 11


Department
Biology
Course Code
BIOL 2040
Professor
Dr

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Cancer Genetics
Cancer is an age related disease; the longer one lives, the higher the risk of cancer.
Stomach cancer is caused by bacteria. Cervical cancer is caused by HPV (a virus).
Cancer is a genetic disease that involved multiple mutations, not single mutations.
They are developed over time. Cancer is not inherited. Certain inherited mutations
could predispose one to cancer because it is multifactorial.
Not all cancers involve somatic parts in an individual; they can be passed along like
a disease. Tasmanian devils can pass their tumors on each other. Cancers can be
infectious.
Oncogenesis is the formation of cancer that begins with the loss of cell cycle
control. Tumors begin with a loss of cell cycle control. Tumor is not necessarily
cancer. Once a tumor completely loses the ability to undergo mitosis, it can
become transformed or immortalized.
There are different types of cancer. Carcinoma refers to cancer of epithelial origin
(skin cancer). Sarcomas are cancers that arise from connective tissues (bone and
cartilage). Leukemia is cancer in blood-forming tissues (marrow). Lymphoma is the
cancer in the cells of the immune system (e.g B cells).
Cancer is the loss of cell cycle control. They are often by mutations.
p53 and pRB are genes involved in cell cycle control that are involved in cancer.
p53 is involved in cell cycle control. At some point cells get the signal to undergo
DNA synthesis. If there is something wrong with the DNA, p53 and p54 control
them. S phase is to allow DNA to be given time to repair, if it does not repair,
apoptosis happens.
p53 is a transcription factor that activates a gene called p21. The product of p21
inactivates cyclin-dependant kinase. Inactivation of cyclin-dependent kinase stops
S phase. p53 is therefore a tumor suppressor. It is a certain checkpoint to stop
DNA synthesis.
Mutations in cancer are involved in mutations in cell cycle control. The involvement
is involved in most types of cancer. It is theh break between the G1 and S phase
from getting activated.
P53 stops working when both copies are mutated. If one copy is working, then it
will work normally. If they both stop working, DNA and the cell will continue to keep
replicating damaged DNA. Aproximates 50% of all cancers are associated with p53.
P53 is not the only gene that is involved to cause cancer. P53 opens the door for
other mutations to start accumulating.
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