genetics ch.19

What can cause a frameshift mutation? A nucleotide deletion A base transition A base transversion A nucleotide addition

A nucleotide deletion A nucleotide addition

What is responsible for silent mutations? The DNA repair systems in a cell Frameshift mutations Reverse mutations The degeneracy of the genetic code

The degeneracy of the genetic code

*Figure The effects of germ-line versus somatic mutations* The embryo on the left carries a germ-line mutation; the one on the right carries a somatic mutation. Which embryo(s) will be able to pass this mutation on to future progeny? The embryo on the left Both embryos The embryo on the right Neither embryo

The embryo on the left

In the mismatch repair system, how is the newly-made daughter strand distinguished from the parental strand? The daughter strand is methylated, while the parental strand is not. The parental strand is acetylated, while the daughter strand is not. The daughter strand is acetylated, while the parental strand is not. The parental strand is methylated, while the daughter strand is not.

The parental strand is methylated, while the daughter strand is not.

The synthesis of DNA over a template strand that harbors some type of DNA damage is called ____ ____-

Translesion synthesis

The following are steps in the nucleotide excision repair (NER) system. Place them in order, starting with the earliest on top. UvrC makes cuts on both sides of the thymine dimer DNA polymerase fills the gap and DNA ligase seals the region UvrB and UvrC are released UvrD removes the damaged region UvrA is released and UvrC binds UvrA/UvrB complex tracks along the DNA in search of damaged DNA

UvrA/UvrB complex tracks along the DNA in search of damaged DNA UvrA is released and UvrC binds UvrC makes cuts on both sides of the thymine dimer UvrD removes the damaged region UvrB and UvrC are released DNA polymerase fills the gap and DNA ligase seals the region

A germ-line mutation is one that occurs in any body cell other than gametes. a sperm or egg cell. any cell after zygote formation. a virus or a bacterial cell.

a sperm or egg cell.

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

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

A new mutation in a gene is MOST LIKELY to be ______ to the organism. helpful harmful neutral (Random mutations are more likely to disrupt the function of a protein and thus be harmful.)

harmful

When a cell repairs a double-strand DNA break by the mechanism of nonhomologous end joining, the original DNA sequence at the repair site may be changed by a short addition. may be changed by a small inversion. may be changed by a small deletion. is always reformed with 100% accuracy.

may be changed by a small deletion.

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.

mismatch

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

mutant

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

photolyase

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

point

*Figure 19.6 Replica plating* This figure shows a technique known as ____ ___

replica plating

Cells of the body other than germ-line cells are called ______ cells. somatic mosaic stem chimera

somatic

A change of one base for another is described as a base ____ mutation.

substitution

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

the cells that produce sperm and eggs.

Translesion DNA polymerases have an error rate of about ______, which is much ______ than replicative polymerases. 10-2 or 10-3; lower (Replicative polymerases have lower error rates than translesion polymerases.) 10-8 or 10-9; higher 10-8 or 10-9; lower (Translesion polymerases have higher error rates than replicative polymerases.) 108 or 109; higher 10-2 or 10-3; higher

10-2 or 10-3; higher

*Figure 19.1* This figure best illustrates what type of mutation? Transition mutation Base substitution Frameshift mutation Nonsense mutation

Base substitution

Which of these human diseases are caused by mutations in genes involved in nucleotide excision repair? Ataxia telangiectasia Dystrophia myotonica Cockayne syndrome Lejeune syndrome Xeroderma pigmentosum

Cockayne syndrome Xeroderma pigmentosum

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

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

Detection → Removal → Replication

True or false: Deleterious mutations that cause the death of a cell are called nonsense mutations. True false question. True(These types of mutations are called lethal mutations.) False

False

True or false: During homologous recombination repair, the two broken ends of DNA are pieced back together. True false question. True (During nonhomologous end joining, the two broken ends of DNA are pieced back together.) False

False

*Table 19.1* The DNA sequence of the coding strand of a gene is depicted in the top of this figure. Below it are four different types of mutations. Which of them are transversion mutations? I IV(This is a frameshift mutation) III II

I III II

In the mismatch repair system, the proteins ______ form a complex that activates _____, which is already bound to a ______ DNA site. MutS/MutL ; MutH ; hemimethylated MutS/MutL ; MutH ; methylated MutS/MutH ; MutL ; methylated MutS/MutH ; MutL ; hemimethylated MutH/MutL ; MutS ; hemimethylated

MutS/MutL ; MutH ; hemimethylated

A mutation that enhances the survival and/or reproductive success of an individual is referred to as a(n) ______ mutation. silent beneficial neutral deleterious

beneficial

Silent mutations are possible because the genetic code is biased. non-overlapping. universal. degenerate.

degenerate.

The breakage of chromosomes is referred to as a(n)___ - ____ break.

double strand

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

embryonic kidney cell. adult muscle cell. brain cell.

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

nonsense

If the patch of white hair in this child were larger, that would indicate a ______. somatic mutation that occurred later during embryonic development germ-line mutation that occurred earlier during embryonic development somatic mutation that occurred earlier during embryonic development germ-line mutation that occurred later during embryonic development

somatic mutation that occurred earlier during embryonic development

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

It suppresses the phenotypic effect of another mutation.

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? Nucleotide excision repair Nonhomologous end joining Base excision repair Mismatch repair system Homologous recombination repair

Mismatch repair system

Eukaryotic homologs for which of the following have been found so far? MutS and MutL MutS and MutH MutH and MutL MutS, MutL and MutH

MutS and MutL

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

Nonhomologous end joining Homologous recombination repair

Which of these mutations changes a mutant allele back to a wild type allele? Conversion Inversion Reversion Transversion

Reversion

What feature is common to diseases caused by defects in the NER system? Multiple choice question. Vulnerability to bacterial pathogens Novel beneficial mutations Special nutritional requirements Sensitivity to sun damage

Sensitivity to sun damage

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

Silent

In the nucleotide excision repair (NER) system, the damaged DNA is recognized by the ______, and removed by the action of the proteins ______. UvrC/UvrD complex; UvrA (endonuclease) and UvrB (helicase) UvrC/UvrD complex; UvrA (helicase) and UvrB (endonuclease) UvrA/UvrB complex; UvrC (endonuclease) and UvrD (helicase) UvrA/UvrB complex; UvrC (helicase) and UvrD (endonuclease) (UvrC is an endonuclease; UvrD is a helicase.)

UvrA/UvrB complex; UvrC (endonuclease) and UvrD (helicase)

Which pair of proteins is required for nucleotide excision repair (NER)? UvrD and N-glycosylase UvrA and photolyase UvrB and AP endonuclease UvrC and DNA ligase

UvrC and DNA ligase

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

both prokaryotes and eukaryotes.

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

breakpoint

A deleterious mutation that results in the death of an organism is known as a(n) ____ mutation.

lethal

True or false: It is healthy for a human to acquire new DNA mutations, because they are the driving force for adaptive evolution. True (Although mutations can be beneficial this is very rare. Most mutations are harmful and can cause diseases such as cancer.) False

False

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

Nonsense mutations

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

missense mutation.

A ____ mutation is one that converts a mutant allele back to the wild type form.

reverse

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

somatic mutations.

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.

suppressor

Translesion DNA polymerases are ______ accurate and ______ sensitive to geometric distortions in DNA than replicative DNA polymerases. more ; less less ; more (Translesion DNA polymerases contain an active site with a loose pocket that can accommodate aberrant structures on the template strand.) less ; less more ; more

less ; less

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.

no change to the amino acid sequence of the polypeptide.

The expression of an intact gene may be altered when it is moved to a new location. This is due to a(n) ______. tautomeric shift X-inactivation breakpoint effect position effect

position effect

A main advantage of nonhomologous end joining is that it does not require a(n) ___ _____, and thus it can take place throughout the cell cycle. Listen to the complete question

sister chromatid

The patch of white hair in this child is most likely caused by a ______ mutation. somatic nonsense reverse germ-line

somatic

Muscle cells, nerve cells, skin cells are examples of mesoderm cells. germ-line cells. somatic cells. stem cells.

somatic cells.

A mutation that occurs directly in a sperm or egg cell, or in one of their precursor cells, is referred to as a(n) ____-___ mutation.

germ line

Cells that give rise to the gametes such as eggs and sperm are called __ ____

germ line

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

typically found in nature.

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

wild type

What can cause double-strand breaks (DSBs)? Gamma rays X-rays Ultraviolet light Reactive oxygen species

Gamma rays X-rays Reactive oxygen species

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

It suppresses the phenotypic effect of another mutation.

Eukaryotic species have homologs to which of the following mismatch repair proteins of E. coli? MutL UvrA (This is an E. coli protein that participates in nucleotide excision repair, and not mismatch repair.) UvrB (This is an E. coli protein that participates in nucleotide excision repair, and not mismatch repair.) MutS MutH

MutL MutS

The addition or deletion of a number of bases that is not a multiple of 3 causes a(n) ______ mutation.

frameshift

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

missense

The following proteins participate in mismatch repair. Match the protein with its appropriate function. MutS MutL MutH MutUExonuclease Detects the mismatch Digests the nonmethylated strand Makes a cut in a nonmethylated strand Separates strands at the cleavage site Acts as a linker that helps loop the DNA

MutS-> Detects the mismatch MutL-> Acts as a linker that helps loop the DNA MutH-> Makes a cut in a nonmethylated strand MutU-> Separates strands at the cleavage site Exonuclease-> Digests the nonmethylated strand

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

Areas within a single gene that are more likely to mutate than other regions are called ______ ____

hot spots

Suppressor mutations that occur within the same gene as the first are called ___ suppressors.

intragenic

*Table 19.3* In this figure, the Xs represent amino acids that are altered due to mutation in a transporter gene. In the last panel, transport is restored due to a(n) mutation.

intragenic suppressor

The restoration of function by a second mutation at a different site in the same gene is known as a(n) tautomeric shift. intragenic suppressor. intergenic suppressor. (An intergenic suppressor involves restoring function through a mutation in a different gene.) position effect.

intragenic suppressor.

*Figure 19.20 Repair of.a double stranded break in DNA via nonhomologous end joining * This figure shows the first steps of the mechanism of DNA repair called ____ ____ _____

nonhomologous end joining

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.

nucleotide excision

The proteins UvrA, UvrB, UvrC, and UvrD are required for the DNA repair system called methyl-directed mismatch repair nucleotide excision repair. base excision repair. homologous recombination repair.

nucleotide excision repair

*Figure 19.3 A postion effect that alters eye color in Drosophila* The eye color gene in this Drosophila mutant (panel B) has been relocated to a heterochromatic chromosomal region, which results in its inactivation in some cells, causing a variegated appearance. This change in the gene's location is said to have a(n)

position effect

A deleterious mutation is best defined as one that decreases the chance of DNA replication. normal chromosome segregation. mRNA transcription. survival and reproduction.

survival and reproduction.

The strand that is repaired in the mismatch repair system is the methylated strand. either the methylated or nonmethylated strand, depending on the type of mismatch. the hemimethylated strand. (Hemimethylated refers to a helix where one strand is methylated and the other is not.) either the methylated or nonmethylated strand, depending on the size of mismatch. (Only one type of strand is selected for repair.) the nonmethylated strand.

the nonmethylated strand.

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

the replication of a template strand that contains DNA damage.

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

up and down

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

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

Hot spots are regions of the chromosome that are rich in heterochromatic DNA segments. are more likely to contain genes than other regions. are more likely to mutate than other regions. are rich in origins of DNA replication.

are more likely to mutate than other regions.

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 question True False (In most cases, DNA repair is indeed a three-step process.)

True

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

has a different DNA sequence from the wild type.

True or false: The nucleotide excision repair system of DNA repair is unique to prokaryotes. True false question. True (NER is found in both eukaryotes and prokaryotes, although it is best understood in prokaryotes.) False

False

*Table 19.1* In this figure, the normal DNA coding sequence of a gene is shown on top, along with four different mutations. Match the mutation to its appropriate description. I II III IV Silent Mutation Nonsense Mutation Frameshift Mutation Missense Mutation

I->Silent Mutation II->Missense Mutation III->Nonsense Mutation IV->Frameshift Mutation

In this figure, the Xs represent mutations in two different protein subunits. The second mutation restores function. What concept does this represent? Position effect Breakpoint effect Intergenic suppression Intragenic suppression (Intragenic suppression occurs when the second mutation is in the same gene as the first.)

Intergenic suppression

*Figure 19.16 Direct repair of damaged bases in DNA* Which enzyme can correct the mutation shown in this figure? Photolyase Photoligase Phosphodiesterase Phosphotransferase

Photolyase

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 frameshift mutation. base pair mismatch. dynamic mutation. base pair tautomer.

base pair mismatch.

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 question. True False (In most cases, DNA repair is indeed a three-step process.)

True

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

bulky, helix distorting lesions.

If an individual possesses a germ-line mutation, then ______ of the gametes produced by the individual will carry the mutation. If an individual possesses a somatic mutation, then ______ of the gametes produced by the individual will carry the mutation. all; none half; none none; half half; all (Somatic cell mutations are not incorporated into gametes.) all; half (Only one of the two alleles is likely to be mutated so only half the gametes are expected to contain the mutated allele.)

half; none

The two main mechanisms used to repair DNA double-strand breaks are ___ recombination repair and ____ end joining.

homologous and nonhomologous

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

point