Genetics Ch19
In the base excision repair (BER) system of E. coli, DNA polymerase I ______.
-replaces the abnormal region with normal nucleotides -removes a segment containing abnormal DNA
What can cause double-strand breaks (DSBs)? -X-rays -Ultraviolet light -Gamma rays -Reactive oxygen species
-X-rays -Gamma rays -Reactive oxygen species
Which of these human diseases are caused by mutations in genes involved in nucleotide excision repair? -Xeroderma pigmentosum -Lejeune syndrome -Ataxia telangiectasia -Cockayne syndrome -Dystrophia myotonica
-Xeroderma pigmentosum -Cockayne syndrome
In the base excision repair (BER) system of eukaryotes, which enzyme can synthesize a short segment of DNA that displaces the original DNA, and what is generated as a result?
DNA polymerase δ or ε ; flap
In the mismatch repair system, how is the newly-made daughter strand distinguished from the parental strand?
The parental strand is methylated, while the daughter strand is not.
Base excision repair (BER) is the main system used in the repair of _____________
abnormal bases
DNA N-glycosylases are enzymes involved in ___________
base excision repair
A position effect can alter gene expression in cases when the gene is moved from a less condensed, or ______________ chromosome, where it is active, to a very highly condensed, or ________________ chromosome, where its expression may be turned off.
euchromatic ; heterochromatic
The protein alkyltransferase can only be used once because it ____________
is inactivated by the addition of a methyl group
Error-prone replication is a characteristic of ______.
lesion-replicating polymerases
The enzyme that can recognize thymine dimers and split them is called ________________
photolyase
In this figure, a gene's expression is changed due to its new location near regulatory sequences, which is an example of the __________ effect.
position
The expression of an intact gene may be altered when it is moved to a new location. This is due to a(n) _________
position effect
The expression of an intact gene may be altered when it is moved to a new location. This is due to a(n) __________
position effect
The eye color gene in this Drosophila mutant (panel b) has been relocated to a heterochromatic chromosome, which resulted in its inactivation. 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 ____________
survival and reproduction
A breakpoint refers to the region _________
where two chromosome pieces break and rejoin with other chromosome pieces
DNA N-glycosylases exist in many types. Which of these abnormal DNA bases can be recognized by these enzymes? -5-methylthymine -7-methylguanine -3-methyladenine -Uracil
-7-methylguanine -3-methyladenine -Uracil
Which changes can cause a frameshift mutation? -A base transversion -A base addition -A base deletion -A base transition
-A base addition -A base deletion
Which are examples of somatic mutations? -A mutation in a sperm cell -A mutation in an embryonic kidney cell -A mutation in an adult muscle cell -A mutation in an egg cell
-A mutation in a sperm cell -A mutation in an embryonic kidney cell
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
-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 point mutations would likely have an inhibitory effect on protein function? -Missense -Nonsense -Frameshift -Silent
-Missense -Nonsense -Frameshift
Which of the following enzymes participate in the base excision repair system of humans? -N-glycosylase -Flap endonuclease -AP endonuclease -Photolyase -Alkyltransferase
-N-glycosylase -Flap endonuclease -AP endonuclease
Double-strand breaks are typically repaired by which of the following? -Photoreactivation -Nucleotide excision repair -Nonhomologous end joining -Methyl-directed mismatch repair -Homologous recombination repair
-Nonhomologous end joining -Homologous recombination repair
Mutations in the 5'-UTR or 3'-UTR of an mRNA molecule are most likely to affect what? -The proper splicing of the mRNA -The mRNA's ability to be translated -The mRNA's ability to be transcribed -The stability of the mRNA
-The stability of the mRNA -The mRNA's ability to be translated
Place the steps of homologous recombination repair in the proper sequence.
1. DSB is processed at the break site 2. Strand exchange 3. DNA synthesis 4. Resolution
Match with proper functions: 1. MutS 2. MutL 3. MutH 4. MutU 5. Exonuclease a. Acts as a linker that helps loop the DNA b. Detects the mismatch c. Makes a cut in a nonmethylated strand d. Separates strands at the cleavage site e. Digests the nonmethylated strand
1.b 2.a 3.c 4. d 5. e
Translesion DNA polymerases incorporate wrong nucleotides with a frequency of approximately _____, which is ______ than the error rate for replicative DNA polymerases.
10(-2) ; higher
In an average human individual, naturally occurring double-strand breaks occur at a rate of _________ per cell per day.
10-100
Which of the following base changes is a transition mutation? -A to T -C to A -A to C -C to G -A to G
A to G
In the base excision repair (BER) system of E. coli, which is the enzyme that removes a DNA segment containing the abnormal region and replaces it simultaneously with normal nucleotides?
DNA polymerase I
T/F: During homologous recombination repair, the two broken ends of DNA are pieced back together.
False
This figure shows what DNA repair system?
Homologous recombination repair
In this figure, two panels are shown. Panel I shows protein A. A first mutation inhibits the function of protein A. In Panel II a second mutation alters protein B to carry out the function of protein A. What is this an example of?
Intergenic suppression
What is the effect of a suppressor mutation?
It suppresses the phenotypic effect of another mutation.
Eukaryotic species have homologs to which of the following mismatch repair proteins of E. coli? -UvrB -MutS -MutH -UvrA -MutL
MutS MutL
In the mismatch repair system, select the two Mut proteins that form a complex, activating a third Mut protein, which is already bound to a hemimethylated DNA site.
MutS/MutL ; MutH
In the nucleotide excision repair (NER) system, select the complex that recognizes damaged DNA, followed by the proteins that act to remove the damaged DNA.
UvrA/UvrB complex; UvrC (endonuclease) and UvrD (helicase)
Which of the following human diseases is associated with a high predisposition to skin cancer because of an inability to repair UV-induced lesions?
Xeroderma pigmentosum
A germ-line mutation is one that occurs in ____________-
a sperm or egg cell
In a neutral mutation, a negatively-charged amino acid is substituted for ______________
another negatively-charged amino acid
In the replica-plating experiment of the Lederbergs, bacterial colonies appeared ____________ of the two secondary plates.
at the same location on each
The Lederbergs' replica-plating experiment demonstrated that _____________
bacteria mutate randomly prior to exposure to viruses
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 __________
base pair mismatch
A mutation that enhances the survival and/or reproductive success of an individual is referred to as a(n) _______________ mutation.
beneficial
Nucleotide excision repair (NER) is the main system used in the repair of ___________
bulky, helix distorting lesions
The term germ line is used to describe the ____________
cells that produce sperm and eggs
A mutant Drosophila fly can land on the side of a fly bottle when the bottle is incubated at 20-23 C but not at 24-27 C. This is an example of a(n) _______________ mutation.
conditional
Mutations that affect the phenotype only under certain circumstances are called __________ mutations.
conditional
AP endonucleases participate in the base excision repair (BER) system. These enzymes ______________ an apurinic/apyrimidinic site.
cut DNA on the 5' side of
Silent mutations are possible because the genetic code is _________
degenerate
Photoreactivation is a repair mechanism that can ___________ a thymine dimer in the ___________ of light.
directly split; presence
The breakage of chromosomes is referred to as a(n) _________________-_______________ break.
double strand
Which of the following is least likely to occur as a result of a double-strand break?
duplications
T/F: The nucleotide excision repair system of DNA repair is unique to prokaryotes.
false -- NER is in both eukaryotes and prokaryotes
The addition or deletion of a number of bases that is not a multiple of 3 causes a(n) _______________ mutation.
frameshift
If an individual possesses a germ-line mutation, then _____________ produced by the individual will carry the mutation. If an individual possesses a somatic mutation, then _________________ produced by the individual will carry the mutation.
half of the gametes ; none of the gametes
A mutant allele is best defined as an allele that _________
has a different DNA sequence from the wild-type
A genetic mosaic is an individual that ____________
has regions of the body that are genotypically different from each other
Defects in the human mismatch repair genes, hMSH2 and hMLH1, play a role in the development of ______.
hereditary nonpolyposis colorectal cancer
An advantage of ___________ is that it provides an error-free mechanism for repairing a DNA double-strand break.
homologous recombination repair
The two main mechanisms used to repair DNA double-strand breaks are ____________ recombination repair and _____________ end joining.
homologous; nonhomologous
An individual that is ____________ for the sickle cell allele has a decreased chance of survival.
homozygous
This figure shows an example of a(n) __________ ___________mutation.
intragenic suppressor
Translesion DNA polymerases are ______ accurate and ______ sensitive to geometric distortions in DNA than replicative DNA polymerases.
less; less
A mutation that results in the death of an organism is known as a(n) _______________ mutation.
lethal
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 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
Hereditary nonpolyposis colorectal cancer is due, in part, to defects in _________ repair.
mismatch
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
A base substitution in DNA that ultimately leads to a change in the encoded amino acid is called a(n) ___________________ mutation.
missense
Sickle cell disease is caused by a __________ mutation in the gene for the ___________ chain.
missense; β-globin
The term ___________ refers to an inherited change in the sequence of the genetic material.
mutation
This figure shows the first steps of the mechanism of DNA repair called ______
nonhomologous end joining
A mutation that results in a premature termination of the synthesis of a polypeptide is called a(n) _______________ mutation.
nonsense
The proteins UvrA, UvrB, UvrC, and UvrD are required for the DNA repair system called ______ repair.
nucleotide excision
Xeroderma pigmentosum and Cockayne syndrome are two human diseases caused by inherited defects in __________ repair.
nucleotide excision
Which enzyme can correct the mutation shown in this figure?
photolyase
The process by which thymine dimers are directly repaired with the help of light is called __________
photoreactivation
According to the ____________ ________________hypothesis, mutations can occur in any gene and do not require the exposure of an organism to an environmental condition or agent.
random mutation
Translesion synthesis refers to the ________
replication of a template strand that contains DNA damage
Which of these mutations changes a mutant allele back to a wild-type allele?
reversion
Bacteria possess ______ DNA repair systems.
several different
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.
sister chromatid
A disadvantage of homologous recombination repair in eukaryotes is that it is dependent on _________
sister chromatids, which are only available during part of the cell cycle
Mutations in body cells that do not go on to form gametes are known as _____________ mutations.
somatic
If the patch of white hair in this child were larger, that would indicate a _____________ mutation that occurred ______________ during embryonic development.
somatic; earlier
The strand that is repaired in the mismatch repair system is ________
the nonmethylated strand
A(n) ___________________ is a type of base substitution that involves a change of a pyrimidine to another pyrimidine, or a purine to another purine.
transition
A base substitution in which a purine and a pyrimidine are interchanged is called a(n) ___________________ mutation.
transversion
The wild type genotype or phenotype is the one that is _________ found in nature.
typically
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; down
Which of the following statements about promoter mutations is true? -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 -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 -Down promoter mutations decrease the affinity of transcription factors to the promoter
The following are steps in the nucleotide excision repair (NER) system. Place them in order
1. UvrA/UvrB complex tracks along the DNA in search of damaged DNA 2. UvrA is released and UvrC binds 3. UvrC makes cuts on both sides of the thymine dimer 4. UvrD removes the damaged region 5. UvrB and UvrV are released 6. DNA polymerase fills the gap and DNA ligase seals the region
Picture: Illustration labeled A shows silent mutations. Illustration labeled B shows missense mutations. Illustration labeled C shows non- sense mutations. Illustration labeled shows addition or deletion mutations. Illustration labeled B and C are transversion mutation in which purine base is replaced by pyrimidine base. This is called point mutation. 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? A; B; C; D
B, C, A
Which polymerase is involved in the base excision repair system of eukaryotes? DNA polymerase β DNA polymerase α DNA polymerase II DNA polymerase I
DNA polymerase β
Which of the following statements about DNA N-glycosylase is true? -Living organisms produce many types, each of which deals with specific types of abnormal bases. -Living organisms produce only one type, which can deal with any abnormal base. -Living organisms produce many types, each of which can deal with any abnormal base. -Living organisms produce only one type, which can deal only with the abnormal base 7-methylguanine.
Living organisms produce many types, each of which deals with specific types of abnormal bases.
Consider a mutation that causes a decreased activity in a particular protein. A second mutation alters the function of another protein that participates in the same cellular pathway, thereby overcoming the defect in the first protein. This is an example of a(n) _______________
intergenic suppressor
Mutations in body cells that do not go on to form gametes are known as __________ mutations.
somatic
What is responsible for silent mutations?
The degeneracy of the genetic code
Suppressor mutations that occur within the same gene as the first are called ______________ suppressors.
intragenic
The restoration of function by a second mutation at a different site in the same gene is known as a(n) __________
intragenic suppressor
This figure best illustrates what type of mutation? (5'-AACGCTAGATC-3' and 3'-TTGCGATCTAG-5' --> 5'-AACGCGAGATC-3' and 3'-TTGCGCTCTAG-5')
base substitution
Consider a DNA that has been exposed to the alkylating agent nitrogen mustard. The protein that can remove the ethyl and methyl groups from the guanine bases is called ________________
alkyltransferase
The mutation shown in this figure is most likely repaired by the enzyme ____________
alkyltransferase that transfers the methyl group onto itself
Replica plating is a technique in which _____________
bacterial colonies are transferred from one plate to another with a sterile piece of velvet cloth
Some errors affect individual nucleotides and do not distort the DNA double helix. These errors are removed primarily by a DNA repair system called BER, which stands for ___________ ___________ repair.
base excision
Suppressor mutations that occur in a different gene from the first mutation are called ____________ suppressors.
intergenic
Bacterial strains that lack one or more DNA repair systems have a very high mutation rate. These are called _________________ strains.
mutator
A change in a single base pair in the genetic material is known as a(n) _____________ mutation.
point
A mutation that does not change the amino acid sequence of a polypeptide is known as a(n) ______________ mutation.
silent
Which of these represents the correct order of steps during a typical DNA repair system?
Detection → Removal → Replication
T/F: Most DNA repair systems involve three major steps: detection of the error, removal of the abnormality, and its replacement with normal DNA.
true
Which of the following base changes are transversion mutations? -A to T -A to C -A to G -C to T -G to A -G to C
-A to T -A to C -G to C
The following are steps in the base excision repair (BER) system. Place them in order
1. N-glycosylase recognizes an abnormal base and cleaves the bond btwn the base and the sugar 2. AP endonuclease recognizes the missing base and cleaves the DNA backbone 3. DNA polymerase removes the damaged DNA and replaces it with normal DNA 4. DNA ligase makes a covalent connection in the DNA backbone
T/F: Deleterious mutations that cause the death of a cell are called nonsense mutations.
False -- they're called lethal mutations
A silent mutation is a mutation that results in no __________
change to the amino acid sequence of the polypeptide
Areas within a single gene that are more likely to mutate than other regions are called ___________ __________
hot spots
A mutation in a gene that causes an amino acid change in the encoded protein is called a ______ mutation.
missense
A(n) ______________ mutation is a missense mutation that has no detectable effect on protein function.
neutral
The _______________ _______________ hypothesis states that the resistance of bacteria to T1 infection should arise as a result of exposure to T1 phage but not before.
physiological adaptation
DNA N-glycosylases participate in the base excision repair (BER) system. These enzymes _____________
remove an abnormal base
Image that is velvet cloth wrapped over the mouth looks like a parmesean shaker. This figure shows a technique known as ________ ________
replica plating
A change of one base for another is described as a base ___________ mutation.
substitution
A change of one base for another is described as a base _________________ mutation.
substitution/point
A missense mutation in the β-globin gene is responsible for sickle cell disease. This mutation causes an altered polypeptide sequence where the sixth amino acid is changed from glutamic acid to ____________
valine
Which pair of proteins is required for nucleotide excision repair (NER)?
UvrC and DNA ligase
The restoration of protein function by a second mutation in a different gene is known as a(n) _____________
intergenic suppressor
An individual that has one copy of the sickle cell allele and one copy of the wild-type allele has an increased level of resistance to the disease _____________
malaria
An intergenic suppressor mutation may involve which of the following?
A change in the expression of one gene that compensates for the loss-of-function mutation in another gene
Which of the following statements regarding somatic and germ-line mutations is true?
A germ-line mutation typically originates during meiosis whereas a somatic mutation typically originates during mitosis.
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
Mutations in eukaryotic genes that change the _________________ recognition sequences may affect the order and/or number of exons contained in the mature mRNA.
splice
