Chapter 23 - Cancer Genetics

Question 1

__ is a disease that is not inherited, but some __ are associated with certain chromosomal __; and some __ occur at higher __ in some families.

Answer 1

Cancer; cancers; abnormalities; cancers; frequencies.

Question 2

What does it mean that cancers are “multiple hit” events? What case ‘bends’ this rule?

Answer 2

Cancers are the result of two or more mutations.

Someone that inherits one mutation is half way to developing cancer which is why some families have higher frequencies.

Question 3

Why does cancer affect most people later in life?

Answer 3

Cancer results from “multiple hit” events, and these events tend to accumulate over time (rather than spontaneously appear rapidly).

Question 4

Many cancer cells are __ due to defects in chromosome segregation during mitosis.

Answer 4

aneuploid

Question 5

The first mutation of a cell usually results in a cell being predisposed to __ at an abnormally high rate. The second mutation causes rapid __. The third mutation causes __ changes to the cell. A forth mutation causes the cell to __ uncontrollably and __ other tissues.

Answer 5

proliferate.
division.
structural.
divide; invade.

Question 6

Dominant mutations that stimulate cell divisions are called __ (__-__ are the normal cellular counterparts).

Answer 6

oncogenes; proto-oncogenes

Question 7

__ tend to be dominant because one copy of the gene is sufficient to cause excessive cell proliferation.

Answer 7

Oncogenes

Question 8

__-__ genes inhibit cell division. Because only one functional copy of the gene is needed for the wt phenotype, mutations leading to cancer are __ (unless the gene is __).

One example is the __-_ gene; this gene’s product functions to prevent cells from progressing through the cell __ if conditions aren’t appropriate.

Answer 8

Tumor-suppressor; recessive; haploinsufficient

Rb-1; cycle

Question 9

Recessive-acting mutations in __-__ genes require a mutation in __ alleles OR a mutation and a __.

Answer 9

tumor-suppressor; both; deletion

Question 10

__ is a rare childhood cancer that is inherited as an autosomal __ mutation. Cells from these patients always show that __ alleles are mutated, so it is __ at the molecular level. It ‘appears’ to be an autosomal __ mutation because there is a 100% chance of developing a __ mutation in at least one __ cell.

Answer 10

Retinoblastoma; dominant.

both; recessive.

dominant; spontaneous; retinal

Question 11

Contributors to cancer include defects in DNA __; mutations affecting chromosome __; mutations affecting DNA __ (and thereby gene expression); mutations in genes for __ (enzyme); and affects on __ (vessel formation) and __ (spreading).

Answer 11

repair; segregation; methylation; telomerase; vascularization; metastasis

Question 12

Many tumors show a wide range of inhibition of __ activity (these are needed for degrading __ or interfering with their __). This may allow __ to be expressed at higher levels.

Answer 12

microRNA; mRNA; translation.

oncogenes

Question 13

CML often involves a reciprocal __ between chromosome __ and __. This causes a fusion between the BCR gene (chromosome __) to a portion of c-ABL (chromosome __) - this chromosome is often referred to as the __ chromosome. The fusion protein is more active in stimulating cell __ and eventually leads to CML.

Answer 13

tranlocation; 22; 9.

22; 9.

Philadelphia.

proliferation.

Question 14

Burkitt Lymphoma is due to over expression of c-Myc normally found on chromosome __; but translocated onto chromosome __.

Answer 14

8; 14

Question 15

Viruses can mutate and rearrange __-__ to create __. They can also alter the expression of host genes because viral genes often have strong __.

Answer 15

proto-oncogenes; oncogenes.

promoters

Question 16

Cancer cells often demonstrate __ changes (they have abnormal __ patterns). __-__ may repress tumor-suppressor genes; __-__ can affect chromosome stability.

Answer 16

epigenetic; methylation.

Hyper-methylation; hypo-methylation.

Question 17

Colorectal cancer usually starts with loss of a normal __-__ gene. A polyp forms and becomes a __ tumor. Activation of an oncogene called __ causes the tumor to grow. Loss of __-__ gene p53 causes the tumor to become __. Another mutation leads to the loss of an __ gene which causes the cancer to spread through the bloodstream.

Answer 17

tumor-suppressor.
benign.
ras
tumor-suppressor; malignant.
antimetastasis.

Question 18

Cancer is a heterogeneous group of disorders resulting from:
A. Rapid, uncontrolled cell division
B. a multistep process that requires several different mutations.
C. accumulation of germ-line mutations during a person’s lifetime
D. Only A & B
E. A, B, and C

Answer 18

D. Only A & B

Question 19

Many cancers are associated with a characteristic chromosomal deletion. Does the deleted region probably contain an oncogene or tumor suppressor?
A. An oncogene because the deletion prevents activation by a transcriptional activator.
B. An oncogene because the deletion created a dominant mutation of the gene.
C. Tumor-suppressor and the gene is likely haploinsufficient and does not make enough protein product with just one functional copy.
D. Could be either an oncogene or tumor-suppressor. Additional information is needed.

Answer 19

C. Tumor-suppressor and the gene is likely haploinsufficient and does not make enough protein product with just one functional copy.