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