Genetic - Chap
Translesion DNA polymerases incorporate wrong nucleotides with a frequency of approximately _____, which is ______ than the error rate for replicative DNA polymerases.
10^(-2) ; higher
Which of these are examples of mutagens?
2-Aminopurine Nitrous acid Nitrogen mustard 5-Bromouracil
Which changes can cause a frameshift mutation?
A base deletion A base addition
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.
Base analogs induce mutations by ______.
being incorporated instead of normal bases during DNA replication
Physical mutagens include
both X-rays and UV light
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 silent mutation is a mutation that results in no ______.
change to the amino acid sequence of the polypeptide
Nitrous acid is a mutagen that acts via the process of ______.
deamination
Silent mutations are possible because the genetic code is ______.
degenerate
Mutations that remove an adenine or guanine from the DNA are known as ______.
depurinations
Alkylating agents covalently attach _______ or _______ groups to DNA bases, and thus disrupt their normal base pairing properties.
methyl ; ethyl
Gene conversion occurs by the action of ______.
mismatch repair DNA gap repair synthesis
A base substitution in DNA that ultimately leads to a change in the encoded amino acid is called a(n) ______ mutation.
missense
A mutation in a gene that causes an amino acid change in the encoded protein is called a ______ mutation.
missense
Sickle cell disease is caused by a ______ mutation in the gene for the ______ chain.
missense; β-globin
DNA gap repair synthesis
restores the stretches of DNA removed by strand degradation at the initiation of recombination.
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
The mutagen nitrous acid changes cytosine to ________ and adenine to _________
uracil ; hypoxanthine
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
A breakpoint refers to the region
where two chromosome pieces break and rejoin with other chromosome pieces
Which are examples of somatic mutations?
- A mutation in an embryonic kidney cell - A mutation in an adult muscle cell
Which of the following are examples of base pair mismatches?
- Adenine on parent strand and Cytosine on daughter strand - Cytosine on parent strand and Adenine on daughter strand - Cytosine on parent strand and Thymine on daughter strand
This figure best illustrates what type of mutation?
Base substitution
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?
C A B
In recombination, what is the process that synthesizes small stretches of DNA to replace those removed by strand degradation?
DNA gap repair synthesis
Which of these represents the correct order of steps during a typical DNA repair system?
Detection → Removal → Replication
Which of the following base changes are transversion mutations?
G to C A to T A to C
A genetic mosaic is an individual that
Has regions of the body that are genotypically different from each other
The first proposal for a set of steps at the molecular level that lead to homologous recombination is called the ________ model.
Holliday
Changes to DNA structure caused by reactive oxygen species (ROS) are termed _________ ________ ________
Oxidative DNA damage
Which of these tests is used to evaluate the mutagenicity of an agent?
The Ames test
What is responsible for silent mutations?
The degeneracy of the genetic code
Most DNA repair systems involve three major steps: detection of the error, removal of the abnormality, and its replacement with normal DNA.
True
Homologous recombination is a process in which
a new combination of DNA sequences is formed through breakage and rejoining of similar or identical DNA segments.
A germ-line mutation is one that occurs in ______.
a sperm or egg cell
Base excision repair (BER) is the main system used in the repair of ______.
abnormal bases
A mutagen is a(n) ______.
agent that causes mutation
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 _______
analogues
In a neutral mutation, a negatively-charged amino acid is substituted for ______.
another negatively-charged amino acid
Photoreactivation is a repair mechanism that can ______ a thymine dimer in the ______ of light.
directly split; presence
The process by which chromosomes exchange similar or identical DNA segments during meiosis is called ______.
homologous recombination
Areas within a single gene that are more likely to mutate than other regions are called _______ ________
hot spots
Trinucleotide repeat expansions are repeated sequences of three nucleotide bases which ______.
increase generation after generation
An allele that has a DNA sequence different from that of the wild-type is called a(n) _______ allele.
mutant
The term _______ refers to an inherited change in the sequence of the genetic material.
mutation
The probability that a gene will be altered by a new mutation is referred to as the _______ ________
mutation ; rate
A(n) ________ mutation is a missense mutation that has no detectable effect on protein function.
neutral
A mutation that results in a premature termination of the synthesis of a polypeptide is called a(n) _______ mutation.
nonsense
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 process by which thymine dimers are directly repaired with the help of light is called
photoreactivation
A change in a single base pair in the genetic material is known as a(n) ________ mutation.
point
A(n) ______ mutation refers to a mutation in which just one base is changed within the DNA sequence.
point
In addition to the DNA strands of the chromosomes involved in homologous recombination, the multiple steps in the pathway require the action of
protein catalyst
The multiple steps of homologous recombination, including strand breakage and rejoining, require the action of ______.
protein catalysts
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.
spontaneous ; induced
A change of one base for another is described as a base ________ mutation.
substitution or point
The phenomenon in which a repeated sequence of three nucleotide bases increases in number generation after generation is called
trinucleotide repeat expansion
Which of these are examples of alkylating agents?
- Ethyl methanesulfonate - Nitrogen mustard
Double-strand breaks are typically repaired by which of the following?
- 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 mRNA's ability to be translated - The stability of the mRNA
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
Which of the following base changes is a transition mutation?
A to G
An individual that has somatic regions with different genotypes is known as a genetic
mosaic
Alkylating agents include nitrogen _________ and ethyl ________
mustard ; methanesulfonate
A mutation that does not change the amino acid sequence of a polypeptide is known as a(n) _______ mutation.
silent
Mutations in body cells that do not go on to form gametes are known as ______ mutations.
somatic
The patch of white hair in this child is most likely caused by a ______ mutation.
somatic
If the patch of white hair in this child were larger, that would indicate a ______ mutation that occurred ______ during embryonic development.
somatic; earlier
Mutations in eukaryotic genes that change the _________ recognition sequences may affect the order and/or number of exons contained in the mature mRNA.
splice
Errors in DNA replication are examples of ______ mutations, while mutations caused by ultraviolet light are ______ mutations.
spontaneous ; induced
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
Which of these point mutations would likely have an inhibitory effect on protein function?
Missense Frameshift Nonsense
Which model for recombination involves production of single-strand breaks in each of the non-sister chromatids after which the strands invade the opposite helices?
Holliday model
What type of mutations involve a change from a normal codon to a stop codon?
Nonsense mutations
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
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
Alkylating agents cause mutations by ______.
disrupting the normal pairing between nucleotides within the DNA
The addition or deletion of a number of bases that is not a multiple of 3 causes a(n) _________ mutation.
frameshift
The Ames test assays whether an agent causes ______.
gene mutations
The mutation rate is commonly expressed as the number of new mutations in a given ______.
gene per cell generation
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
Translesion DNA polymerases are ______ accurate and ______ sensitive to geometric distortions in DNA than replicative DNA polymerases.
less ; less
Hot spots are regions of the chromosome that are ______.
more likely to mutate than other regions
An agent that can change DNA structure and cause mutations is known as a(n)
mutagen
If a heteroduplex includes a region with an allelic difference, the cell will ______.
repair the mismatch to either the dominant or recessive allele