Chapter 15: Mutation, DNA Repair, and Cancer

What are the typical functions of proteins encoded by genes that may become oncogenes?

- Intracellular signaling protein - Transcription factor - Growth factor receptor

What are the three most common ways that the function of a tumor-suppressor gene is lost?

- Mutation within the gene - Loss of the chromosome that carries the gene - Abnormal DNA methylation near the gene's promoter

Xeroderma pigmentosum and Cockayne syndrome are genetic diseases that affect ______.

DNA repair

Which of the following are ways that chemical mutagens covalently modify the structure of nucleotides?

Deamination of bases, Alkylation of bases

Which of the following DNA repair systems can detect and correct damaged or altered DNA bases?

Direct repair, Base excision repair, Nucleotide excision repair

Which of the following are causes of spontaneous mutations?

Insertion of a transposon into a gene, Free radicals produced during metabolic processes that change nucleotide structure, Errors made by DNA polymerase during replication

What is the function of the p53 protein?

It is a transcription factor

Intracellular signaling protein

Ras

When GTP is bound, ___________ promotes cell division

Ras

Which of the following viruses can cause cancer?

Rous sarcoma virus, hepatitis B, papillomavirus, epstein-barr virus

What missense mutation is least likely to affect protein function?

Substitution of a positively charged amino acid for another positively charged amino acid

What does a gene mutation affect?

The sequence of bases in a particular gene

What would result from a single nucleotide deletion (point mutation) within the coding sequence of a structural gene?

a frameshift mutation, producing a different amino acid sequence altogether

Which of the following are ways that point mutations may alter a gene?

a nucleotide is added to a gene, the base sequence within a gene is changed, a nucleotide is removed from a gene

Which of the following organisms have the ability to repair DNA and thus minimize mutations?

all living things

Test ability of substance to cause mutation

ames test

If DNA damage is too severe, the p53 protein will activate genes that promote ______.

apoptosis

A silent mutation results in a polypeptide with an unchanged amino acid sequence because the genetic code is ______.

degenerate

A repair enzyme recognizes an incorrect structure. The incorrect structure is converted back to a correct structure.

direct repair

Enzyme removes a modification

direct repair

Which of the following is NOT a typical cellular change that occurs during lung cancer?

elevated gas transport

The timing of a mutation during development has negligible effects on the severity of the genetic defect.

false

Addition or deletion of nucleotides that are not multiples of 3, completely different amino acid sequence downstream from mutation

frameshift mutation

Ionizing radiation can produce which of the following?

free radicals

Relatively small changes in DNA sequence are known as:

gene mutations

Give rise to gametes, can occur in a sperm or egg cell or in cell that gives rise to eggs and sperm

germ-line

New mutation are more likely to be ___________ than ____________

harmful, beneficial

The activity of an oncogene is:

higher than that of the normal gene

Lost normal growth regulation, invasive (can invade healthy tissue), metastatic (can migrate to other parts of the body)

malignant stage

Occurs last during cancer progression?

metastasis

A base pair mismatch is detected. A portion of the DNA strand containing the mismatch is removed and then replaced with new DNA.

methyl-directed mismatch repair

Which of the following CANNOT be repaired by nucleotide excision repair (NER)?

mismatched bases

Assume each of the following letters represents an amino acid. What type of gene mutation occurred to produce the following protein sequence? Normal: JAYBIRDCATPAW Mutated: JAYBIRDBATPAW

missense

Changes a single amino acid in a polypeptide, may not alter function if substituted amino acid is similar in chemistry to original

missense mutation

A heritable change in the genetic material

mutation

Alkylates bases

nitrogen mustard

Deaminates bases

nitrous acid

Has less energy and can only penetrate the surface

nonionizing radiation

Change from a normal codon to a stop or termination codon (produces a truncated polypeptide)

nonsense mutation

Most common DNA repair system

nucleotide excision repair (NER)

Affects only a single base pair

point mutation

A mutation may alter the sequence within a _________ and affect the rate of ____________

promoter, transcription

Involved in cell growth, mutation causes this gene to be overactive, uncontrolled cell growth occurs

proto-oncogene

Have normal cellular function to promote cell division when signaling pathway turned "on"

proto-oncogenes

Mutations may occur in __________ ____________ or ____________ ______________

regulatory elements, operator sites

A physician discovered a cancerous tumor in the cartilage of a patient. What type of tumor is this?

sarcoma

An abnormal base or nucleotide is recognized. A portion of the damaged strand is removed and replaced with new DNA.

base excision and nucleotide excision repair

In order for cancer cells from a lung carcinoma to metastasize, they must penetrate the ______ membrane, which is a sheetlike layer of extracellular matrix that provides a barrier between the lung cells and the bloodstream.

basement

Inserts between bases of the double helix, causing additions and deletions

benzo(a)pyrene

How do point mutations affect DNA sequences?

by adding or subtracting a single base pair by substituting one base for another

A disease caused by gene mutations

cancer

Disease of multicellular organisms that is characterized by uncontrolled cell division

cancer

The Rous sarcoma virus is an example of a virus that causes ______.

cancer

About 80% of all human cancers are related to exposure to _______________

carcinogens

Which of the following is the cancer of epithelial cells?

carcinoma

Which of the following are typical cellular changes that occurs during lung cancer?

cellular hyperplasia, loss of ciliated cells, cellular dysplasia, increases in basal cell number and thickening of epithelium

What are the two basic alterations in a mutation?

change base sequence, add or remove nucleotides

Some tumor-suppressor genes encode proteins that test the integrity of the genome and prevent a cell from progressing past a certain stage in the cell cycle. These proteins are termed ___________ proteins.

checkpoint

Two different chromosomes break, and the ends of the broken chromosomes fuse with each other incorrectly

chromosomal translocations

A mutation may affect the amino acid sequence of a polypeptide only if it occurs within the ______.

coding sequence of a structural gene

Disease that is the result of a single amino acid substitution

sickle-cell

Does not alter the amino acid sequence, genetic code is degenerate

silent mutation

All other body cells, can occur early or late in development

somatic cells

What type of mutation results from abnormalities that naturally occur during biological processes?

spontaneous

Result from abnormalities in biological processes

spontaneous mutations

Silent mutations have no effect on the amino acid sequence of a polypeptide because ______.

the base substitution results in a codon that specifies the same amino acid as the original sequence

Where must a mutation occur if it is to directly affect an amino acid sequence?

the coding region of a structural gene

In nucleotide excision repair, what serves as the template for synthesis of new DNA to replace the damaged strand?

the complementary strand of DNA

A site where two adjacent thymine bases become covalently cross-linked to each other.

thymine dimer

UV rays can cause formation of _________________ ______________ causing gaps or incorporation of incorrect bases

thymine dimer

True or false: All living things possess mechanisms allowing them to minimize mutation.

true

An overgrowth of cells with no useful purpose

tumor

Involved in stopping cell growth, if eliminated cancer can occur, normally encodes a protein that prevents cancer

tumor-suppressor gene

Which of the following statements are true about nucleotide excision repair (NER)?

-The undamaged strand is used as a template to synthesize a normal strand. -A region of several nucleotides in the damaged strand is removed from the sequence.

Arrange the events that occur in nucleotide excision repair in E. coli in the correct order, beginning with the first step at the top of the list.

1. The UvrA-UvrB complex identifies a damaged site 2. UvrC makes cuts on both sides of the damaged region 3. UvrD binds and removed the damaged region 4. DNA polymerase synthesizes new DNA to fill the gap 5. DNA ligase seals the newly synthesized DNA to the original strand

Acts as a base analogue

5-bromouracil

Which of the following base pairs would be targeted and repaired by a mismatch repair system?

A-G

You are a brilliant graduate student and you are skeptical of the results found by the Lederbergs. You decide to repeat their experiment, but you do not have ready access to T1 bacteriophage. What might you use instead?

Ampicillin, an antibiotic that inhibits growth of bacterial cell wall

Can lead to effects on gene expression that ultimately affect cell division, and thereby lead to cancer

DNA alterations

DNA repair requires ....

DNA damage to be detected, repair of DNA damage

Cells are normally limited to one DNA repair system that corrects DNA mistakes.

False

In which phases of the cell cycle are the three checkpoints located?

G2, metaphase, G1

What are the two main functions of tumor suppressor genes?

Negative regulation of cell division Maintenance of genome integrity

Which of the following are chemical mutagens?

Nitrous acid, Benzo(a)pyrene, Nitrogen mustard, Ethyl methanesulfonate

Which of the following is true concerning a somatic cell mutation?

Only a small group of cells within the organism is affected by the mutation.

The rate of transcription for a gene is found to be affected by a mutation. Where would you expect the mutation to appear on the DNA?

in the promotor for the gene

Brought on by environment agents, mutation rate higher than spontaneous mutation rate

induced mutations

Exposure to chemical mutagens can lead to mutations because chemical mutagens can cause:

insertions and deletions during DNA replication, inappropriate base pairing during DNA replication

Has high energy and short wavelength

ionizing radiation

May promote cancer by keeping the cell division signaling pathway in a permanent "on" position

oncogene

Mutations can cause the proto-oncogene to become an _______________ or cancer promoting gene

oncogene

May decrease ability of Ras to hydrolyze GTP or exchange GDP for GTP faster

oncogenic mutations

Expected rate of background mutation approximately ___ mutation for every __________ genes

one, one million

Activated when DNA is damaged

p53

Mutagenic agents can be divided into two broad categories:

physical or chemical