MCB Chapter 15 Review

How do somatic mutations affect an individual's offspring?

The mutation does not occur in germ line cells and therefore does not affect offspring.

How does the protein encoded by the ras oncogene differ from the protein encoded by the normal ras gene?

The protein encoded by the oncogene is unable to hydrolyze GTP.

A compound is subjected to the Ames test to evaluate its ability to cause mutation. If the substance is a mutagen, what results are expected?

There will be more bacterial colonies on the plate exposed to the mutagen than on the control plate.

How do growth factors promote cell division?

They activate pathways that trigger gene transcription.

How do environmental agents that cause induced mutations affect the mutation rate?

They increase the mutation rate compared to the spontaneous mutation rate.

How do nonsense mutations affect protein function?

Translation is terminated where the mutation occurs, producing a truncated polypeptide which is unlikely to function correctly.

The four proteins involved in nucleotide excision repair in E. coli are called, in alphabetical order:

UrA; UvrB; UvrC; UvrD

In E. coli, the four key proteins comprising the nucleotide excision repair (NER) system are called:

UvrA, UvrB, UvrC, and UvrD

A mutation is best defined as:

a heritable change in the genetic material

What is an oncogene?

a mutant gene that promotes uncontrolled cell growth

What is a point mutation?

a mutation that affects only a single base pair

What is a mutagen?

a physical or chemical agent that causes mutations

A missense mutation may not affect protein structure and function if the altered amino acid has:

a similar side chain

What is a thymine dimer?

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

Match each stage that occurs in the development of a lung carcinoma with the correct description. dysplasia

abnormal cell morphology

The p53 protein can arrest the cell cycle at the G1 stage by:

activating genes that encode proteins that stop the cell cycle

What are somatic cells?

all cells of the body that are not germ line cells

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

all living things

The __________ test is used to evaluate the ability of a substance to cause mutations. It employs a bacterium that cannot synthesize the amino acid histidine.

ames

Gene ________ is a genetic event in which the number of copies of a gene is increased.

amplification

A normal proto-oncogene may become an oncogene if it is:

amplified translocated to a different chromosome mutated

What is gene amplification?

an increase in the number of copies of a gene

In response to severe DNA damage that is too extensive to be repaired, the p53 protein will activate other genes that promote

apoptosis

In most cases, how many genetic changes in a cell lineage typically occur before cancer develops?

at least 10

Which of the following are ways that ionizing radiation can alter DNA structure?

base deletion breaks in one or both DNA strands

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

A __________ tumor is precancerous and has not spread throughout the body.

benign

How do point mutations affect DNA sequences? Choose all that apply.

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

How can a missense mutation in a proto-oncogene cause cancer?

by altering the function of the encoded protein

How can a chromosomal translocation cause cancer?

by creating an abnormal gene that encodes a fusion protein

How can gene amplification of a proto-oncogene cause cancer?

by generating too much of the encoded protein

A carcinogen is a chemical or physical agent that promotes:

cancer

The Rous sarcoma virus is an example of a virus that causes:

cancer

The disease of multicellular organisms that is characterized by uncontrolled cell division is known as

cancer

Agents that increase the likelihood of developing cancer are known as

carcinogens

Ultraviolet light and some chemicals in cigarette smoke are examples of mutagens called ________ because they are known to cause cancer.

carcinogens

A ______ is a cancer of epithelial cells.

carcinoma

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

checkpoint

What proteins monitor the integrity of the genome and prevent a cell from progressing through a certain point in the cell cycle?

checkpoint proteins

The effects of _________ mutagens on DNA structure is varied. Some can alkylate bases, others act as base analogues, and a few can insert between bases in the double helix and cause additions or deletions.

chemical

Mutagenic agents can be divided into two broad categories:

chemical or physical

What type of genetic change promotes cancer by causing the production of an abnormal fusion protein?

chromosomal translocation

Which of the following genetic changes can convert a proto-oncogene into an oncogene?

chromosomal translocations gene amplifications retroviral insertions missense mutations

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

coding sequence of a structural gene.

What are the two types of proteins that are responsible for advancing a cell through the phases of the cell cycle?

cyclins cyclin-dependent kinases

The two proteins that advance a cell through the four phases of the cell cycle are called

cyclins, cyclin-dependent, kinases

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

deamination of bases alkylation of bases

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

degenerate

An alkylated base is recognized by an enzyme. The enzyme removes the alkyl group and restores the normal base structure. What type of DNA repair is this?

direct repair

Which type of DNA repair involves an enzyme that recognizes an incorrect structure in a base and restores the base to its original structure?

direct repair

Tumor-suppressor genes lead to cancer by mutations that:

eliminate their function

Induced mutations are caused by:

environmental agents

What is the purpose of the Ames test?

evaluation of the ability of a substance to cause mutation

Mutations that occur in noncoding sequences may affect gene

expression

True or false: All mutagens are physical agents, such as radiation.

false

True or false: An oncogene is a mutated version of a normal gene. The oncogene is less active than the normal gene.

false

True or false: Cancer usually requires only one or two genetic changes to the same cell lineage.

false

True or false: Nonsense and frameshift mutations generally result in less dramatic changes to a polypeptide sequence than missense mutations.

false

True or false: The function of a normal tumor-suppressor gene is to promote cell division.

false

What type of mutation is the result of the insertion or removal of nucleotides that does not occur in multiples of three?

frameshift

In what types of cells do germ-line mutations occur?

gamete-producing precursors sperm egg

Which of the following are examples of ionizing radiation?

gamma rays X-rays

Relatively small changes in DNA sequence are known as:

gene mutations

Cells that give rise to gametes, such as egg and sperm cells, are known as the

germ line cells

Gametes are produced by:

germ line cells

Animal cells are classified into two main types. Which ones?

germ-line cells somatic cells

Geneticists classify cells of animals into two types: ________-line cells and __________cells.

germ-line, somatic

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

growth factor receptor transcription factor intracellular signaling protein

The public is chiefly concerned about mutagens for the following reasons (select all that apply):

harmful mutations in their children development of cancer

Exposure to agents that result in induced mutations causes the mutation rate of a cell to be ________ than the spontaneous mutation rate.

higher

The activity of an oncogene is:

higher than that of the normal gene

The gene that encodes the Ras protein becomes an oncogene when a mutation reduces the ability of the protein to:

hydrolyze GTP

Mutations can be divided into two main types. Spontaneous mutations result from abnormalities in biological processes, while __________ mutations are caused by environmental agents that enter the cell and alter the structure of DNA.

induced

Which of the following are causes of spontaneous mutations?

insertion of a transposon into a gene errors made by DNA polymerase during replication free radicals produced during metabolic processes that change nucleotide structure

X-rays and gamma rays are examples of __________ radiation, which is a type of electromagnetic radiation that can create free radicals.

ionizing

Which of the following are examples of somatic cells? Choose ALL that apply.

liver cells skin cells muscle cells

The two main functions of tumor suppressor genes are:

maintenance of genome integrity negative regulation of cell division

Tumors that are cancerous, spreading throughout the body and invading healthy tissues are ______.

malignant

Mutations in noncoding sequences:

may affect gene expression

The process by which cancerous cells spread through the body via the bloodstream or surrounding body fluids is termed

metastasis

The process that occurs when cancer cells spread into the blood and other parts of the body is known as

metastasis

Which of the following steps occurs last during cancer progression?

metastasis

Which DNA repair system detects and repairs base pairs that are not bonded correctly?

methyl-directed mismatch repair

Which of the following exhibit nucleotide excision repair (NER)?

mice humans bacteria plants

A specific type of point mutation called a(n) __________ mutation is a base substitution that changes a single amino acid in a polypeptide sequence.

missense

What type of mutation changes a single amino acid in a polypeptide sequence?

missense

Agents that cause mutation are known as

mutagens

Most carcinogens are also:

mutagens

A heritable change in genetic material is known as a(n)

mutation

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

Cancer usually affects older people because they are likely to have more:

mutations

Select all of the following that are chemical mutagens.

nitrous acid nitrogen mustard benzopyrene ethyl methanesulfonate

Consider the following four types of point mutations. Match each to its effect on the polypeptide sequence. silent mutation

no effect

UV light is an example of:

nonionizing radiation

What type of mutation changes a normal codon to a termination codon?

nonsense

_________ mutation involves a change from a normal codon to a stop codon.

nonsense

A mutant gene that results in uncontrolled cell growth is known as a(n)

oncogene

Consider a normal gene that is needed for growth. If this gene becomes overactive, it may contribute to cancer. It then becomes a(n)

oncogene

Over the past four decades, researchers have identified many types of ______. Examples include growth factor receptors, transcription factors, and intracellular signaling proteins.

oncogenes

Consider the following four types of point mutations. Match each to its effect on the polypeptide sequence. missense mutation

one amino acid is changed to another

When oncogenes are ______ compared to proto-oncogenes, they can promote certain types of cancer.

overactive

The protein product of what tumor-suppressor gene acts to sense DNA damage, promote DNA repair, and halt cell division?

p53

Select all of the following that are tumor-suppressor genes.

p53 Rb

X-rays and ultraviolet light are examples of ______ mutagens.

physical

A(n) ______ mutation affects only a single base pair.

point

Nucleotide excision repair (NER) is found in:

prokaryotes and eukaryotes

A missense mutation in a(n) _____________-oncogene can convert it to a cancer-promoting gene if the mutation alters the function of the encoded protein to allow for increased cell division.

proto

A normal gene that can become an oncogene if it is mutated is called a(n)

proto oncogene

On occasion, a retrovirus may insert its DNA into a host chromosome near a(n) ________-__________. This may result in the overexpression of this type of gene, thereby promoting cancer.

proto-oncogene

Which of the following genes is an oncogene?

ras

Individuals affected by xeroderma pigmentosum are likely to develop skin cancer because they cannot __________ UV-induced lesions.

repair

Xeroderma pigmentosum causes a predisposition to skin cancer because it impairs the ability to:

repair UV-induced lesions

Bacterial colonies can be transferred from a master plate to secondary plates in the same configuration using a transferring agent such as a sterile velvet cloth. This technique is known as

replica plating

What is the process in which bacterial colonies are transferred from a master plate to secondary plates in the same configuration using a transferring agent such as a sterile velvet cloth?

replica plating

A(n) __________ is a tumor of connective tissue such as bone or cartilage.

sarcomas

What type of mutation has no effect on the amino acid sequence of a polypeptide?

silent

All cells of the body that are not part of the germ line are called

somatic cells

Sperm and egg cells are termed germ line cells. In contrast, cells of the skin, muscle, heart, and liver are examples of

somatic cells

Germ-line mutations may occur in ___________ cells, ____________ cells, or in the precursor cells that produce them.

sperm ; egg

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

spontaneous

Name the gene that causes Rous sarcoma:

src

Rous sarcoma researchers discovered the __________ gene that was present in chicken sarcomas but absent in mutant RSV strains that infected and proliferated within chicken cells, without transforming them into malignant cells.

src

What missense mutation is least likely to affect protein function?

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

In response to DNA damage, p53 will arrest the cell cycle at:

the G1 checkpoint

Consider the following four types of point mutations. Match each to its effect on the polypeptide sequence. frameshift mutation

the amino acid sequence is changed downstream of the mutation

Amplification of a proto-oncogene can lead to cancer if it increases:

the amount of protein produced

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

Nonionizing radiation, such as ultraviolet light, can lead to:

the formation of a thymine dimer

What does a gene mutation affect?

the sequence of bases in a particular gene

Match each stage that occurs in the development of a lung carcinoma with the correct description. metastasis

the spread of cancer cells through the bloodstream

What is metastasis?

the spread of cancerous cells through the bloodstream or body fluids

Somatic mutations are not transmitted to an individual's offspring because:

they do not occur in the gametes

Match each stage that occurs in the development of a lung carcinoma with the correct description. hyperplasia

thickening of the epithelium

Ultraviolet light can cause the formation of a(n) __________ in DNA.

thymine dimer

A nonsense mutation causes the of the _________ protein to be terminated prematurely. This reduces the length of the polypeptide and thus alters its function.

translation

A genetic alteration called a chromosomal _________ occurs when one segment of a chromosome becomes attached to a different chromosome.

translocation

Which of the following terms describes the movement of a DNA segment from one chromosome to another?

translocation

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

true

An overgrowth of cells is known as a(n) __________ , which can be benign or become cancerous.

tumor

Genes encoding proteins involved in the regulation of normal cell growth and thus the prevention of cancer are called

tumor supressor genes

Elimination of the function of a(n) ______ gene promotes cancer.

tumor-suppressor

The protein p53 is encoded by a(n):

tumor-suppressor gene

Genes that normally function to prevent cancerous growth are called:

tumor-suppressor genes

Maintenance of genome integrity and negative regulation of cell division are the two main functions of:

tumor-suppressor genes

Which of the following genes encode proteins that help prevent cancer?

tumor-suppressor genes

What type of radiation is nonionizing and only penetrates the surface of biological materials?

ultraviolet light

Which of the following genetic diseases affect DNA repair systems in humans?

Cockayne syndrome xeroderma pigmentosum

What protein is inhibited by the Rb protein?

E2F

Consider the following four types of point mutations. Match each to its effect on the polypeptide sequence. nonsense mutation

an amino acid codon is changed to a stop codon

What is a tumor?

an overgrowth of cells

What type of tissue is a sarcoma derived from?

connective tissue

The Ames test uses a strain of Salmonella typhimurium that cannot synthesize:

histidine

The Rb protein blocks cell division by:

inhibiting the E2F transcription factor

The gene that encodes the Ras protein is an example of a(n):

oncogene

Mutations that do not alter the amino acid sequence of a polypeptide are known as

silent mutations

Ultraviolet light can cause the formation of a(n) _________ in DNA

thymine dimer

True or false: A few viruses are known to cause cancer.

true

Arrange the steps in a growth factor signaling pathway that promotes cell division in the correct order, with the first step at the top.

1. A growth factor binds to a receptor and activates it. 2. An intracellular signal transduction pathway is activated. 3. Transcription factors in the nucleus are activated. . Genes that promote cell division are transcribed.

Arrange the stages of cancer progression in the correct order. Start with the earliest form at the top.

1. benign growth 2. malignant growth 3. metastasis.

Place the following types of mutations in order from the least effect on polypeptide sequence at the top to the most dramatic effect on polypeptide sequence at the bottom.

1. silent 2. missence 3. nonsense

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 site 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

Consider a germ-line mutation that occurs in a sperm which fertilizes a normal egg to produce a zygote. In the individual that results from this zygote, ________% of the cells will contain the mutation, and ________% of the gametes produced by that individual will carry the mutation.

100%, 50%

When the addition or deletion of nucleotides does not occur in a multiple of __________ nucleotides, the result is a frameshift mutation.

3

A mutation in a germline cell has a(n) ________ percent chance of being transmitted from parent to child.

50%

Approximately what percentage of human cancers are associated with mutations of the p53 gene?

50%

Mutations of the p53 gene are involved in approximately what percentage of human cancers?

50%

What is the chance that a mutation in a parent's germ line cells will be passed on to his or her offspring?

50%

What is a proto-oncogene?

A normal gene that can become an oncogene if it is mutated.

Which of the following are ways that point mutations may alter a gene? Choose all that apply.

A nucleotide added to a gene. The base sequence within the gene is changed. A nucleotide is removed from a gene.

Select all of the following that are true about nucleotide excision repair (NER).

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

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

APOPTOSIS

How do the effects of germ-line mutations in a parent progress over the lifetime of an offspring receiving that mutation?

All of the cells of the individual's body, but only half of the gametes produced by that individual will carry the mutation.

The type of DNA repair that corrects defects due to normal nucleotides being incorrectly base-paired is called___________ - mismatch repair.

CH3 Directed

In the Ames test, you expose S. typhimurium cells that cannot synthesize histidine to compound X, then plate them on a medium lacking histidine. The next day you observe a higher number of colonies on this plate versus the control plate, which has bacteria with no exposure. What reasonable conclusion can you draw?

Compound X is a mutagen

Match each protein involved in nucleotide excision repair in E. coli with its function. UvrC

Cuts DNA on both sides of the damaged site

The p53 protein is encoded by a tumor-suppressor gene which is expressed when _______ is damaged

DNA

The expression of the p53 gene is induced in response to:

DNA damage

Xeroderma pigmentosum and Cockayne syndrome are genetic diseases that affect:

DNA repair

The three checkpoints that will stop the cell cycle if genetic abnormalities are detected are found in the following phases:

G1, G2, metaphase

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

G2 G1 Metaphase

Arrange the events that occur in the progression of lung cancer in the correct order, beginning with the first event at the top.

Hyperplasia Loss of ciliated cells Dysplasia Metastasis

Match each protein involved in nucleotide excision repair in E. coli with its function. UvrA/UvrB complex

Identifies a damaged site

What is the function of the Rb protein?

It inhibits cell division.

What is the function of the p53 protein?

It is a transcription factor.

Which of the following best describes the retinoblastoma (Rb) gene?

It is a tumor-suppressor gene involved in the negative regulation of cell division.

What two mechanisms enable a retrovirus to promote cancer?

It may insert its DNA near proto-oncogenes. It may carry an oncogene in its genome.

Which of the following statements is TRUE?

Larger genes are more likely to incur a mutation than smaller genes.

What statement about carcinogens is true?

Most of them are also mutagenic.

Match each protein involved in nucleotide excision repair in E. coli with its function. UvrD

Removes the damaged region

What organism is used in the Ames test?

Salmonella typhimurium

Match each protein involved in nucleotide excision repair in E. coli with its function. DNA ligase

Seals newly synthesized DNA to the original strand

Match each protein involved in nucleotide excision repair in E. coli with its function. DNA polymerase

Synthesizes new DNA to fill in the gap

__________ is a site where two adjacent thymine bases become covalently cross-linked to one another.

THYMINE DIMER