Ch.25: Genetics Basis of Cancer

Question 1

Describe cancer’s multistep process

Answer 1

-At the cellular and genetic levels,
It begins with a precancerous genetic change (that is, a
benign growth)

-Following additional genetic changes, it progresses to
cancerous or malignant cell growth

-Once a cancerous cellular growth has become malignant, the
cells are invasive (that is, they can invade healthy tissues)

-Cancerous cells are also metastatic (that is, they can migrate
to other parts of the body

Question 2

What is an oncogene?

Answer 2

a mutant gene that is overexpressed or hyperactive and contributes to abnormal cell growth and cancerous growth

Question 3

What is a tumor-suppressor gene?

Answer 3

a gene that prevents cancer and the proliferation of cancer cells; Loss-of-function mutations in these genes allow cancerous growth to occur

Question 4

How many copies of proto-oncogenes need to be effected to cause cancer- why? How many copies of tumor-suppressor genes need to be effected to cause cancer?

Answer 4

-Because there are two copies of most genes, only one copy of proto-oncogenes need to be effected

-both copies of tumor-suppressor genes usually need to be inactivated to cause cancer

Question 5

What are proto-oncogenes?

Answer 5

normal cellular genes that can be mutated into an oncogene

Question 6

How are most cancers caused?

Answer 6

by mutations in multiple genes, but the order of the mutations is not necessarily important

Question 7

How do tumor cells present?

Answer 7

They often have missing, extra and rearranged chromosomes

Question 8

What is a predisposition for developing cancer?

Answer 8

inherited mutations in either oncogenes or tumor suppressor genes

Question 9

Where are abnormalities common in cancer cells?

Answer 9

in chromatin modification