Ch 19

It is a gene mutation, a point mutation, a base substitution, a transition mutation a deleterious mutation, a mutant allele, a nonsense mutation, a conditional mutation, and a temperature-sensitive lethal mutation.

A gene mutation changes a base pair from AT to GC. This change causes a gene to encode a truncated protein that is nonfunctional. An organism that carries this mutation cannot survive at high temperatures. Make a list of all the genetic terms that could be used to describe this type of mutation.

It could be called a point mutation as a single base pair was substituted. It could also be called a transition because the purine A changed to another purine G and the T pyrimidine was changed to another pyrimidine C. Because the mutation yields a truncated protein, it could also be called a nonsense mutation. It is also a deleterious mutation because it lowers the organism's chance of survival assuming it will regularly be exposed to high temperatures, but it could also be called a conditional mutation if it appears phenotypically normal a lower temperatures and the temperature of its environment is normally low or fluctuating.

A gene mutation changes an AT base pair to a GC pair. This causes a gene to encode a truncated protein that is nonfunctional. An organism that carries this mutation cannot survive at high temperatures. Make a list of all the genetic terms that could be used to describe this type of mutation.

has a different DNA sequence from the wild type.

A mutant allele is best defined as an allele that can no longer be transcribed into mRNA. has a different DNA sequence from the wild type. encodes a protein that causes a disease.

missense mutation.

A mutation in a gene that causes an amino acid change in the encoded protein is called a sense mutation. missense mutation. nonsense mutation. silent mutation.

silent

A mutation that does not change the amino acid sequence of a polypeptide is known as a(n) ____________ mutation.

nonsense

A mutation that results in a premature termination of the synthesis of a polypeptide is called a(n) ___________ mutation.

harmful

A new mutation in a gene is MOST LIKELY to be ______ to the organism. helpful neutral harmful

suppressor

A second mutation that occurs in a different site than the first mutation, and which converts the mutant back to the wild-type phenotype, is best referred to as a(n) _________ mutation.

no change to the amino acid sequence of the polypeptide.

A silent mutation is a mutation that results in no change to the nucleotide sequence of the DNA. no expression of the protein encoded by the gene. no change to the nucleotide sequence of the messenger RNA. no change to the amino acid sequence of the polypeptide.

temporary change in base structure.

A tautomeric shift is a base change caused by chemical agents. base change caused by ultraviolet light. temporary change in base structure. temporary change in gene expression.

tautomeric shift

A temporary change in base structure due to movement of hydrogen atoms is called a(n) ________ ________

point

A(n) ______ mutation refers to a mutation in which just one base is changed within the DNA sequence. point allele core locus

The mutation rate is the number of new mutations per generation. There are 13 babies who did not have a parent with achondroplasia; thus, 13 is the number of new mutations. To calculate the mutation rate as the number of new mutations per generation, we divided 13 by 2,844,000. The mutation rate is 4.6 x 10^-6.

Achondroplasia is a rare form of dwarfism. It is caused by an autosomal dominant mutation within a single gene. Among 1,422,000 live births, the number of babies born with achondroplasia was 31. Among those 31 babies, 18 of them had one parent with achondroplasia. The remaining babies had two unaffected parents. What is the mutation rate for achondroplasia?

frameshift mutations.

Acridine dyes cause inversion mutations. transition mutations. frameshift mutations. transversion mutations.

disrupting the normal pairing between nucleotides within the DNA.

Alkylating agents cause mutations by creating thymine dimers that block DNA replication. disrupting the normal pairing between nucleotides within the DNA. forming free radicals that damage DNA structure. being incorporated instead of normal bases during DNA replication.

mutagen

An agent that can change DNA structure and cause mutations is known as a(n) ________

mutant

An allele that has a DNA sequence different from that of the wild type is called a(n) ____________ allele.

oxidative stress

An imbalance between the production of reactive oxygen species and an organism's ability to break them down is known as _____________ __________.

a. an A has been transverted into a T. The codon was GGA and became GGT. Both codons code for the same amino acid, so this is a silent mutation. b. missense mutation. The codon GGA was changed to CGA which codes for a different amino acid. C. GAT was changed to GTT. Missense mutation, as the amino acids are different. d. Frame shift. An A was added

Are each of the following mutations silent, missense, nonsense, or frameshift mutations? Original DNA strand is: 5'-ATGGGACTAGATACC-3' a. 5'-ATGGGTCTAGATACC-3' b. 5'-ATGCGACTAGATACC-3' c. 5'-ATGGGACTAGTTACC-3' d. 5'-ATGGGACTAAGATACC-3'

Yes, a person with cancer is a genetic mosaic. The cancerous tissue contains gene mutations that are not found in noncancerous cells of the body.

As discussed in chapter 22, most forms of cancer are caused by environmental agents that produce mutations in somatic cells. Is an individual with cancer considered a genetic mosaic? Explain why or why not.

aminopurine bromouracil

Base analogs include 2-___________ and 5-_________.

being incorporated instead of normal bases during DNA replication.

Base analogs induce mutations by being incorporated instead of normal bases during DNA replication. creating thymine dimers that block DNA replication. forming reactive oxygen species that damage DNA structure. inserting into the DNA and so distorting its helical structure.

tautomers

Bases which exist in keto and enol or amino and imino forms are best described as diasteriomers. enantiomers. topoisomers. tautomers.

germ line

Cells that give rise to the gametes such as eggs and sperm are called ____________ ________.

analogs

Certain compounds have a structure similar to normal DNA bases and so can be incorporated into daughter strands during DNA replication. These compounds are called base _________

nucleotide excision repair: an abnormal base or nucleotide is first recognized and removed from the DNA, and a segment of DNA in this region is excised, and then the complementary DNA strand is used as a template to synthesize a normal DNA strand. mismatch repair: similar to excision repair except that the DNA defect is a base pair mismatch in the DNA, not an abnormal nucleotide. The mismatch is recognized, and a segment of DNA in this region is removed. The parental strand is used as a template to synthesize a normal daughter strand of DNA.

Discuss the similarities and differences between the nucleotide excision repair and mismatch repair systems.

A spontaneous mutation originates within a living cell. It may be due to spontaneous changes in nucleotide structure, errors in DNA replication, or products of normal metabolism that may alter the structure of DNA. The causes of induced mutations originate from outside the cell. They may be physical agents, such as UV light or X rays, or chemicals that act as mutagens. Both spontaneous and induced mutations may cause a harmful phenotype such as cancer. In many cases, induced mutations are avoidable if the individual can prevent exposure to the environmental agent that acts as a mutagen.

Distinguish between spontaneous and induced mutations. Which are more harmful? Which are avoidable?

Nonhomologous end joining Homologous recombination repair

Double-strand breaks are typically repaired by which of the following? Nonhomologous end joining Nucleotide excision repair Homologous recombination repair Methyl-directed mismatch repair Photoreactivation

mismatch

During DNA replication, a base that does not obey the normal AT/GC base pairing rule is added. This type of mutation is most likely corrected by the _________ repair system.

base pair mismatch.

During the normal course of DNA replication, the addition of a nucleotide that does not obey the AT/GC rule of base pairing creates a dynamic mutation. base pair mismatch. frameshift mutation. base pair tautomer.

spontaneous; induced

Errors in DNA replication are examples of ______ mutations, while mutations caused by ultraviolet light are ______ mutations. frameshift; point point; frameshift spontaneous; induced induced; spontaneous

brain cell. adult muscle cell. embryonic kidney cell.

Examples of somatic mutations include a mutation occurring in a(n) brain cell. egg cell. adult muscle cell. embryonic kidney cell. sperm cell.

mytonic fragile

Examples of trinucleotide repeat expansion (TRNE) disorders include ___________ muscular dystrophy and ____________ X syndrome.

A position effect has occurred when the expression of a gene has been altered due to a change in its position along a chromosome.

Explain what the term position effect means.

Cuts are made on both sides of the damaged region so that it can be removed by UvrD.

Explain why cuts are made on both sides of the damaged region of DNA

ionizing

Gamma rays and X-rays are examples of a type of radiation called ___________ radiation.

Nitrous acid can change a cytosine to uracil. Nucleotide excision repair could remove the defect and replace it with the correct base.

Give an example of a mutagen that can change cytosine to uracil. Which DNA repair system(s) would be able to repair this defect?

In part B, the DNA sequence of the eye color gene has not been changed. The change in its expression is due to a position effect.

Has the DNA sequence of the eye color be changed in part B compared with part A? How do we explain the phenotypic difference?

It forms free radicals that can introduce breaks into the DNA molecule.

How does ionizing radiation cause mutations? It forms free radicals that can introduce breaks into the DNA molecule. It forms modified bases with altered base pairing properties. It forms thymine dimers that interfere with DNA replication. It forms intercalating agents that insert between bases and distort the DNA.

a nonsense mutation would probably inhibit protein function, particularly if it was near the end of the coding sequence

How would each of the following types of mutations affect protein function or the amount of functional protein that is expressed from a gene? a. nonsense mutation

a missense mutation may or may not affect protein function, depending on the nature of the amino acid substitution and whether the substitution is in a critical region of the protein.

How would each of the following types of mutations affect protein function or the amount of functional protein that is expressed from a gene? b. missense mutation

An up promoter mutation would increase the amount of functional protein

How would each of the following types of mutations affect protein function or the amount of functional protein that is expressed from a gene? c. up promoter mutation

such a mutation may affect protein function if the alteration in splicing changes and exon in the mRNA that results in a protein with a different structure.

How would each of the following types of mutations affect protein function or the amount of functional protein that is expressed from a gene? d. mutation that affects splicing

You would expose the bacteria to the physical agent. You could also expose the bacteria to the rat liver extract, but it is probably not necessary for two reasons. First, a physical mutagen is not something a person would eat. Therefore, the actions of digestion via the liver are probably irrelevant if you are concerned that the agent might be a mutagen. Second, the rat liver extract would not be expected to alter the properties of a physical mutagen.

How would you modify the ames test to evaluate physical mutagens? Would it be necessary to add the rat liver extract? Explain why or why not.

Mismatch repair system

If the proofreading ability of a DNA polymerase fails, which of the following DNA repair systems is most likely to detect the resulting mutations and fix them? Mismatch repair system Nucleotide excision repair Homologous recombination repair Base excision repair Nonhomologous end joining

a. detect DNA damage

In nucleotide excision repair in E. coli, the function of the UvrA/UvrB complex is to a. detect DNA damage b. make cuts on both sides of the damage c. remove the damaged piece of DNA d. replace the damaged DNA with undamaged DNA

Mutations occurred randomly in the master plate in absence of the evolutionary pressure tested (bacteriophages). Thus, when the colonies were exposed to bacteriophages, the colonies that had randomly developed resistance to them prior to their introduction survived.

In the replica plating experiments, bacterial colonies appeared at the same locations in each of two secondary plates. What explains this result?

The effects of mutations are cumulative. If one mutation occurs in a cell, this mutation will be bassed to the daughter cells. If a mutation occurs in the daughter cell, it will then have two mutations. These two mutations will be passed to the next generation of daughter cells, and so forth. The accumulation of many mutations eventually kills the cells. That is why mutagens are more effective at killing dividing cells than nondividing cells. It is because the number of mutations accumulates to a lethal level. There are two main side effects to these treatments. First, some normal (noncancerous) cells of the body, particularly skin cells and intestinal cells, are actively dividing. These cells are also killed by chemotherapy and radiation therapy. Secondly it is possible that the therapy may produce mutations that will cause noncancerous cells to become cancerous. For these reasons, there is a maximal recommended dose for chemotherapy or radiation therapy.

In the treatment of cancer, the basis for many types of chemotherapy and radiation therapy is that mutagens are more effective at killing dividing cells than nondividing cells. Explain why. What are possible harmful side effects of chemotherapy and radiation therapy?

free radicals

Ionizing radiation produces chemically reactive molecules known as ____________ _______. These are mutagenic because they alter the structure of DNA.

Random mutations are more likely to be harmful than beneficial. The genes within each species have evolved to work properly. They have functional promoters, coding sequences, terminators, and so on, that allow them to be expressed. Mutations are more likely to disrupt these sequences. For example, mutations within the coding sequence may produce early stop codons, frameshift mutations, and missense mutations that result in a nonfunctional polypeptide. On rare occasions, however, mutations are beneficial; they may produce a gene that is expressed better than the original gene or produced a polypeptide that functions better.

Is a random mutation more likely to be beneficial or harmful? Explain your answer

up down

Mutations that occur in a promoter sequence can be divided into two types: ______________ promoter mutations increase the transcription rate, while ____________ promoter mutations decrease it.

depurinations.

Mutations that remove an adenine or guanine from the DNA are known as depyrimidinations. decarboxylations. deaminations. depurinations.

5-bromouracil is a base analogue of thymine

Name a mutagen that is a base analog.

long wavelength and low energy.

Nonionizing radiation is characterized by long wavelength and high energy. short wavelength and low energy. long wavelength and low energy. short wavelength and high energy.

both prokaryotes and eukaryotes.

Nucleotide excision repair (NER) is found in neither eukaryotes nor prokaryotes. eukaryotes but not prokaryotes. both prokaryotes and eukaryotes. prokaryotes but not eukaryotes.

bulky, helix distorting lesions.

Nucleotide excision repair (NER) is the main system used in the repair of small, helix non-distorting lesions. abnormal bases. bulky, helix distorting lesions. mismatched bases.

To show that antibiotic resistance is due to random mutations, you could follow the same basic strategy as lederberg and lederberg did, except the secondary plates would contain the antibiotic instead of the T1 phage. If the antibiotic resistance arose as a result of random mutation on the master plate, you would expect the antibiotic-resistant colonies to appear at the same locations on two different secondary plates.

Outline how you would use the technique of replica plating to show that antibiotic resistance is due to random mutations

reactive oxygen

Products of oxygen metabolism, such as hydrogen peroxide, superoxide, and hydroxyl radical, are collectively called __________________ ______________ species.

bacterial colonies are transferred from one plate to another with a sterile piece of velvet cloth.

Replica plating is a technique in which bacterial colonies are transferred from one plate to another with a sterile glass pipette. bacterial colonies are transferred from one plate to another with a sterile piece of velvet cloth. bacteria are grown in broth then allowed to replicate to produce colonies.

apurinic

The covalent bond between deoxyribose and a purine base is rather unstable and can undergo a spontaneous reaction with water. The breaking of the bond releases the base, and leaves a(n) __________ site in the DNA.

photolyase

The enzyme that can recognize thymine dimers and split them is called _________.

deamination

The mutagen nitrous acid changes cytosine to uracil, and adenine to hypoxanthine, through the process of _________.

in a given gene per cell generation.

The mutation rate is commonly expressed as the number of new mutations in a given chromosome per cell generation. in a given gene per genome size. in a given gene per cell generation. in a given genome per population.

mutation rate

The probability that a gene will be altered by a new mutation is referred to as the _____________ ________________.

breakpoint

The region where two chromosome pieces break and re-attach to other chromosome pieces is called a chromosomal _____________.

depurination

The removal of a purine from DNA is called _________

deamination

The removal of an amino group from a base is called ____________.

the cells that produce sperm and eggs.

The term germ line is used to describe the cells that produce sperm and eggs. the region where cells form the cleavage furrow during mitosis. the cells that defend again microbes. the area where chromosomes line up during cell division.

homologous nonhomologous

The two main mechanisms used to repair DNA double-strand breaks are ___________recombination repair and _____________ end joining.

typically found in nature.

The wild type genotype or phenotype is the one that is never found in nature. rarely found in nature. always found in nature. typically found in nature.

replica plating

This figure shows a technique known as ______________ ______________.

ultraviolet light.

Thymine dimers are typically caused by ultraviolet light. base analogs. alkylating agents. tautomeric shifts. ionizing radiation.

the replication of a template strand that contains DNA damage.

Translesion synthesis refers to the replication strategy employed by nucleotide excision repair (NER) proteins. the replication of a template strand that contains DNA damage. the first step of the mechanism of homologous recombination repair. the last step of the mechanism of nonhomologous end joining.

True; CAG is a codon for glutamine

Trinucleotide repeat expansions (TNREs) are associated with several different human inherited diseases. Certain types of TNREs produce a long stretch of the amino acid glutamine within the encoded protein. When a TNRE exerts its detrimental effect by producing a glutamine stretch, are the following statements true or false? C. The trinucleotide sequence is CAG.

True

Trinucleotide repeat expansions (TNREs) are associated with several different human inherited diseases. Certain types of TNREs produce a long stretch of the amino acid glutamine within the encoded protein. When a TNRE exerts its detrimental effect by producing a glutamine stretch, are the following statements true or false? a. the TNRE is within the coding sequence of the gene

False; the TNRE is not within the promoter, it is within the coding sequence.

Trinucleotide repeat expansions (TNREs) are associated with several different human inherited diseases. Certain types of TNREs produce a long stretch of the amino acid glutamine within the encoded protein. When a TNRE exerts its detrimental effect by producing a glutamine stretch, are the following statements true or false? b. the TNRE prevents RNA polymerase from transcribing the gene properly

False; CCG is a codon for proline

Trinucleotide repeat expansions (TNREs) are associated with several different human inherited diseases. Certain types of TNREs produce a long stretch of the amino acid glutamine within the encoded protein. When a TNRE exerts its detrimental effect by producing a glutamine stretch, are the following statements true or false? d. the trinucleotide sequence is CCG.

which increase generation after generation.

Trinucleotide repeat expansions are repeated sequences of three bases which increase in number via reciprocal translocations. which increase generation after generation. which are used as templates to repair damaged DNA. which are associated with various cancers.

False

True or false: It is healthy for a human to acquire new DNA mutations, because they are the driving force for adaptive evolution. True False

True

True or false: Most DNA repair systems involve three major steps: detection of the error, removal of the abnormality, and its replacement with normal DNA. True False

False NER is found in both eukaryotes and prokaryotes, although it is best understood in prokaryotes.

True or false: The nucleotide excision repair system of DNA repair is unique to prokaryotes. True False

The underlying genetic defect that causes xeroderma pigmentosum is a defect in one of the genes that encode a polypeptide involved with nucleotide excision repair. Individuals with this disease are defective at repairing DNA abnormalities such as thymine dimers and abnormal bases. Therefore, they are very sensitive to environmental agents such as UV light, which is more likely to cause mutations in these people compared to unaffected individuals. For this reason, people with XP development pigmentation abnormalities and premalignant lesions, and they have a high predisposition to skin cancer.

What is the underlying genetic defect that causes xeroderma pigmentosum? How can the symptoms of this disease be explained by the genetic defect?

Gamma rays Short wavelength High energy

Which of the following terms is associated with ionizing energy? Near Ultraviolet light Gamma rays Short wavelength Long wavelength Low energy High energy

Detection → Removal → Replication

Which of these represents the correct order of steps during a typical DNA repair system? Replication → Removal → Detection Detection → Removal → Replication Detection → Replication → Removal Replication → Detection → Removal

deamination of cytosine making uracil or adenine to hypoxanthine

Which process includes the replacement of amino groups with keto groups by nitrous acid?

Oxidative stress

Which term refers to the imbalance between an organism's production of ROS and the ability to break them down? Oxidative stress Anaerobic effect Aerobic deficiency Reductive strain

in trinucleotide repeat expansion (TRNE), a sequence of repeating triplets that is normally a certain length in a healthy individual gets extended, more triplets are added to the sequence. This lengthening occurs in procreation. Severity increases both over the generations, which is called anticipation or dynamic mutation.

With regard to TNRE, what is meant by the term anticipation?

c. less, inhibits

a down promoter mutation causes the promoter of a gene to be _________ like the consensus sequence __________ transcription a. less, stimulates b. more. stimulates c. less, inhibits d. more, inhibits

b. 5-bromouracil.

a mutagen that is a base analog is a. ethyl methanesulfonate (EMS) b. 5-bromouracil. c. UV light d. proflavin

a. an intergenic suppressor

a mutation in one gene that reverses the effects of a mutation in a different gene is a. an intergenic suppressor b. an intragenic suppressor c. an up promoter mutation d. a position effect.

b. over damaged DNA, have low fidelity

an advantage of translesion-replicating polymerases that they can replicate ___________, but a disadvantage is that they ____________. a. very quickly, have low fidelity b. over damaged DNA, have low fidelity c. when resources are limited, are very slow d. over damaged DNA, are very slow.

Both types of repair systems recognize an abnormality in the DNA and excise the abnormal strand. The normal strand is then used as a template to synthesize a complementary strand of DNA. The systems differ in the types of abnormalities they detect. The mismatch repair system detects base pair mismatches, while the nucleotide excision repair system recognizes thymine dimers, chemically modified bases, missing bases, and certain types of crosslinks. The mismatch repair system operates immediately after DNA replication, allowing it to distinguish between the daughter strand (which contains the wrong base) and the parental strand. The nucleotide excision repair system can operate at any time in the cell cycle.

discuss the similarities and differences between nucleotide excision repair and the mismatch repair system.

Mismatch repair is aimed at eliminating mismatches that may have occurred during DNA replication. In this case, the wrong base is in the newly made strand. The binding of MutH, which occurs on a hemimethylated sequence, provides a means of distinguishing between the unmethylated and methylated strands. In other words, MutH binds to the Hemimethylated DNA in a way that allows the mismatch repair system to distinguish between which strand is methylated and which is not.

during mismatch repair, why is it necessary to distinguish between the template strand and the newly made daughter strand? How is this accomplished?

a. significantly higher, is

in an Ames test, a ____________ number of colonies is observed if a substance __________ a mutagen, compared with the number of colonies for a control sample that is not exposed to the suspected mutagen a. significantly higher, is b. significantly higher, is not c. significantly lower, is d. significantly lower, is not

b. the mutations occurred on the master plate prior to T1 exposure and prior to replica plating

in the replica plating experiments of the lederbers, bacterial colonies appeared at the same loctions on each of two secondary plates because a. T1 phage caused the mutations to happen b. the mutations occurred on the master plate prior to T1 exposure and prior to replica plating c. both a and b are true d. neither a nor b is true

not appropriate, because the second mutation occurred in a different codon.

lactose permease is encoded by the lacY gene of the lac operon. Suppose a mutation occured at codon 64 that changed the normal glycine codon to a valine codon. The mutant lactose permease is unable to function. However, a second mutation, which changes codon 50 from an alanine codon to a threonine codon, is able to restore function. Is each of the following terms appropriate or inappropriate to describe this second mutation? a. reversion

appropriate

lactose permease is encoded by the lacY gene of the lac operon. Suppose a mutation occured at codon 64 that changed the normal glycine codon to a valine codon. The mutant lactose permease is unable to function. However, a second mutation, which changes codon 50 from an alanine codon to a threonine codon, is able to restore function. Is each of the following terms appropriate or inappropriate to describe this second mutation? b. intragenic suppressor

not appropriate, because the second mutation affected the same gene as the first mutation.

lactose permease is encoded by the lacY gene of the lac operon. Suppose a mutation occured at codon 64 that changed the normal glycine codon to a valine codon. The mutant lactose permease is unable to function. However, a second mutation, which changes codon 50 from an alanine codon to a threonine codon, is able to restore function. Is each of the following terms appropriate or inappropriate to describe this second mutation? c. intergenic suppressor

appropriate

lactose permease is encoded by the lacY gene of the lac operon. Suppose a mutation occured at codon 64 that changed the normal glycine codon to a valine codon. The mutant lactose permease is unable to function. However, a second mutation, which changes codon 50 from an alanine codon to a threonine codon, is able to restore function. Is each of the following terms appropriate or inappropriate to describe this second mutation? d. missense mutation

c. a hairpin, DNA replication

one way that TNRE may occur involves the formation of _________ that disrupts __________ a. a double-strand break, chromosome segregation b. an apurinic site, DNA replication c. a hairpin, DNA replication d. a free radical, DNA structure

the probability is 75%

when dna replication occurs over an apurinic site, what is the probability that a mutation will occur?

the deamination of methylcytosine is more difficult to repair because thymine is a normal base found in DNA. This makes it difficult for DNA repair enzymes to distinguish between the correct and altered base.

which of these two changes is more difficult for DNA repair systems to fix correctly? Explain why

c. thymine dimers

The function of a photolyase is to repair a. double-strand breaks b. apurinic sites c. thymine dimers d. all of the above

translesion synthesis

The synthesis of DNA over a template strand that harbors some type of DNA damage is called ___________ __________.

thymine dimers

Ultraviolet light causes the formation of crosslinked __________ _________ in DNA.

thymine dimer formation is often the result of exposure to UV light. It most commonly occurs in skin cells.

What is a common cause of thymine dimer formation in people, and in what cell type(s) is it most likely to occur?

An advantage of NHEJ as a DNA repair system is that it can occur at any stage of the cell cycle. A disadvantage is that it may be imprecise and result in a short deletion in the DNA.

What is an advantage and a disadvantage of this repair system?

It suppresses the phenotypic effect of another mutation.

What is the effect of a suppressor mutation? It suppresses the phenotypic effect of another mutation. It suppresses the division of a prokaryotic cell. It suppresses the activity of a cytoplasmic protein. It suppresses the expression of a eukaryotic gene.

Nitrous acid causes mutations that change A to G or C to T, which are transition mutations

What type of mutation (transition, transversion, or frameshift) would you expect each of the following mutagens to cause? a. nitrous acid

5-bromouracil is an analog of Thymine, and causes a bond to G rather than to to A, which is a transition mutation.

What type of mutation (transition, transversion, or frameshift) would you expect each of the following mutagens to cause? b. 5-bromouracil

proflavin causes small additions or deletions which may result in frame shift mutations.

What type of mutation (transition, transversion, or frameshift) would you expect each of the following mutagens to cause? c. Proflavin

Nonsense mutations

What type of mutations involve a change from a normal codon to a stop codon? Frameshift mutations Inversion mutations Missense mutations Nonsense mutations

Photolyase

Which enzyme can correct the mutation shown in this figure? Phosphotransferase Photolyase Photoligase Phosphodiesterase

2-aminopurine 5-bromouracil

Which of the following are base analogs? 2-aminopurine 5-bromouracil 4-iodopyrimidine 3-methyladenine

Cytosine on parent strand and Thymine on daughter strand Cytosine on parent strand and Adenine on daughter strand Adenine on parent strand and Cytosine on daughter strand

Which of the following are examples of base pair mismatches? Cytosine on parent strand and Thymine on daughter strand Cytosine on parent strand and Guanine on daughter strand Cytosine on parent strand and Adenine on daughter strand Adenine on parent strand and Cytosine on daughter strand Adenine on parent strand and Thymine on daughter strand

X-rays Gamma rays

Which of the following are examples of ionizing radiation? X-rays Visible light Near Ultraviolet light Gamma rays

No, the early apple-producing trait affects the entire tree

Which of the following examples is likely to be caused by a somatic mutation? c. One apple tree, in a very large orchard, produces apples 2 weeks earlier than any of the other trees.

Contains low energy Includes ultraviolet light

Which of the following statements about nonionizing radiation are true? Contains low energy Penetrates deep into biological tissues Includes X-rays Includes ultraviolet light

Down promoter mutations decrease the affinity of transcription factors to the promoter Up promoter mutations cause the promoter sequence to be more like the consensus sequence

Which of the following statements about promoter mutations is true? Down promoter mutations decrease the affinity of transcription factors to the promoter Down promoter mutations occur in the 3'-UTR of the gene Up promoter mutations occur in the coding sequence of the gene Up promoter mutations cause the promoter sequence to be more like the consensus sequence

MutH distinguishes between the parental strand and the newly made daughter strand which ensures that the daughter strand is repaired.

Which of the three Mut proteins is responsible for ensuring that the mismatched base in the newly made daughter strand is the one that is removed?

Nitrogen mustard Ethyl methanesulfonate

Which of these are examples of alkylating agents? Hydroxyl radical Acridine orange Nitrogen mustard Ethyl methanesulfonate Ethidium bromide

2-Aminopurine Nitrous acid Nitrogen mustard 5-Bromouracil

Which of these are examples of mutagens? 2-Aminopurine Nitrous acid Guanine Cytosine Nitrogen mustard 5-Bromouracil Adenine

Huntington disease Fragile X syndrome Myotonic muscular dystrophy

Which of these are trinucleotide repeat expansion disorders? Huntington disease Fragile X syndrome Myotonic muscular dystrophy Marfan syndrome Duchenne muscular dystrophy

The Ames test

Which of these tests is used to evaluate the mutagenicity of an agent? The Kirby-Bauer test The Ames test The Pasteur test The Phenol coefficient test

b. nonsense mutation

a mutation changes a codon that specifies tyrosine into a stop codon. This type of mutation is a a. missense mutation b. nonsense mutation c. frameshift mutation d. neutral mutation

d. any of the above

a point mutation could be caused by a. depurination b. deamination c. tautomeric shift d. any of the above

the base analog 5-bromouracil causes a transition

does a 5-bromouracil cause a transition or a transversion?

d. either a or b.

double-strand breaks can be repaired by a. homologous recombination repair (HRR) b. nonhomologous end joining (NHEJ) c. nucleotide excision repair (NER). d. either a or b.

b. deamination

nitrous acid replaces amino groups with keto groups, a process called a. alkylation b. deamination c. depurination d. crosslinking

a reactive oxygen species is a molecule that contains oxygen and may react with cellular molecules in a way that may cause harm.

what is a reactive oxygen species?

enzymes within the rat liver extract may convert nonmutagenic molecules into mutagenic agents. Adding the extract allows researchers to identify molecules that may be mutagenic in mammals.

what is the purpose of the rat liver extract in this procedure?

d. Both b and c

which of the following DNA repair systems may involve the removal of a segment of DNA strand? a. Direct repair b. Nucleotide excision repair c. Mismatch repair d. Both b and c

d. both a and c are examples of somatic mutations

which of the following is an example of a somatic mutation? a. a mutation in an embryonic muscle cell b. a mutation in a sperm cell c. a mutation in an adult nerve cell d. both a and c are examples of somatic mutations

c. a mutation caused by UV light

which of the following is not an example of a spontaneous mutation? a. a mutation caused by an error in DNA replication b. a mutation caused by a tautomeric shift c. a mutation caused by UV light d. all of the above are spontaneous mutations

methyl or CH3 ethyl, CH2CH3, or CH3CH2

Alkylating agents covalently attach ______________ or _____________ groups to DNA bases, and thus disrupt their normal base pairing properties.

mustard methanesulfonate

Alkylating agents include nitrogen _________ gas and ethyl ___________ (EMS).

wild-type

In a natural population, a ________-__________ genotype is the most common one.

deamination.

Nitrous acid is a mutagen that acts via the process of demethylation. alkylation. carboxylation. deamination.

trinucleotide repeat expansion

The phenomenon in which a repeated sequence of three bases increases in number generation after generation is called . ____________ ___________ ___________

apurinic

The red arrow in this figure points to a(n) ______ site.

deamination.

This figure highlights the process of deamination. decarboxylation. depurination. depyrimidination.

Enol Imino Keto Amino

Which of the following are forms of tautomers? Enol Imino Acetal Keto Amino

yes

Which of the following examples is likely to be caused by a somatic mutation? a. a purple flower has a small patch of white tissue

No, the albino trait affects the entire individual

Which of the following examples is likely to be caused by a somatic mutation? b. One child, in a family of seven, is alvino.

yes

Which of the following examples is likely to be caused by a somatic mutation? d. a 60-year-old smoker develops lung cancer

missense

A base substitution in DNA that ultimately leads to a change in the encoded amino acid is called a(n) ___________ mutation.

where two chromosome pieces break and rejoin with other chromosome pieces.

A breakpoint refers to the region of the cell cycle where chromosomes are more susceptible to breaking. where two chromosome pieces break and rejoin with other chromosome pieces. where the two sister chromatids of a replicated chromosome are joined.

point

A change in a single base pair in the genetic material is known as a(n) _________ mutation.

agent that causes mutations.

A mutagen is a(n) agent that causes mutations. protein that repairs mutated DNA. organism that has undergone a mutation.

a somatic mutation is not passed from parent to offspring

Can this trait be passed to offspring?

inserting themselves between adjacent bases and thus distorting DNA structure.

Intercalating agents like acridine dyes induce mutations by forming reactive oxygen species that damage DNA structure. inserting themselves between adjacent bases and thus distorting DNA structure. disrupting the normal pairing between nucleotides within the DNA. creating thymine dimers that block DNA replication.

short wavelength and high energy.

Ionizing radiation is characterized by long wavelength and low energy. short wavelength and low energy. short wavelength and high energy. long wavelength and high energy.

spontaneous induced

Mutations can be caused in two main ways: (1) ______________ mutations are the result of natural biological or chemical processes; and (2) _________ mutations are produced by environmental agents.

somatic mutations.

Mutations in body cells that do not go on to form gametes are known as somatic mutations. germ-line mutations. conditional mutations. auxotrophic mutations.

both X-rays and UV light.

Physical mutagens include X-rays but not UV light. UV light but not X-rays. both X-rays and UV light. neither X-rays nor UV light.

products of oxygen metabolism in all aerobic organisms.

Reactive oxygen species (ROS) are organisms that can only grow in the presence of oxygen. products of oxygen metabolism in all aerobic organisms. organisms that have adverse reactions when grown in oxygen. products of metabolism in the absence of oxygen.

nucleotide excision

Some errors create bulky distortions of the double helix. These errors are removed primarily by a DNA repair system called NER, which stands for ___________ ____________repair.

gene mutations.

The Ames test assays whether an agent causes gene mutations. cancer. DNA repair. chromosomal rearrangements.