Smart book 19

In an average human individual, naturally occurring double-strand breaks occur at a rate of ______ per cell per day.

10-100

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

Apurinic site

What can cause double-strand breaks (DSBs)?

Reactive oxygen species X-rays Gamma rays

Nucleotide excision repair (NER) is found in ______.

both prokaryotes and eukaryotes

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

frameshift

For a tautomeric shift to cause a mutation, it must occur ______.

immediately prior to DNA replication

The common stable form of guanine and thymine is the ______ form.

keto

Bacterial strains that lack one or more DNA repair systems have a very high mutation rate. These are called ____ strains.

mutator

A(n) ____ mutation is a missense mutation that has no detectable effect on protein function.

neutral

Which of the following are examples of base pair mismatches?

- 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 are involved in crossing over?

- Exchange of corresponding chromosome segments - Alignment of a pair of homologous chromosomes - Breakage of non-sister chromatids at analogous locations

Which of the following base changes are transversion mutations?

A to C, G to C, A to T

Which process involves the exchange of corresponding segments of a homologous chromosome pair?

Crossing over

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

False

Which of the following are forms of tautomers?

Keto Imino Enol Amino

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

Which term refers to the imbalance between an organism's abilities to produce reactive oxygen species (ROS) and to break them down?

Oxidative stress

The figure shows two sets of chromosomes after the resolution phase of homologous recombination. Which set consists of chromosomes that show no recombination for the alleles but do have a heteroduplex region?

Top set

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

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. Multiple choice question.

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

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

In a neutral mutation, a negatively-charged amino acid is substituted for ______.

another negatively-charged amino acid

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.

apurinic site

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

The heteroduplex regions in the figure were created by the process of ____ ____ , which occurs as a Holliday junction migrates.

branch migration

Homologous recombination that produces a new combination of alleles occurs through ______.

crossover between homologous chromosomes during meiosis

In the resolution phase of recombination, ______.

either recombinant or non-recombinant chromosomes will be produced, depending on which DNA strands are involved in the cutting and rejoining

Of the four bases normally found in DNA, ____ is most vulnerable to oxidation.

guanine

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

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

missense

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

mutagens

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

mutant

A heritable change in the genetic material is called a(n) ______.

mutation

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

Breakage and rejoining of DNA strands to produce separate chromosomes at the end of recombination is called ______.

resolution

The process of separating two chromosomes that were joined by a Holliday junction is called

resolution

Bacteria possess ______ DNA repair systems.

several different

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

silent

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 mutation; earlier

The wild type genotype or phenotype is the one that is ______ found in nature.

typically

The base cytosine is deaminated to produce the base

uracil

Which processes are involved in homologous recombination according to the Holliday model?

- Single strands invade the opposite helix - Heteroduplex regions form when homologous regions are not identical - A nick occurs at identical sites in one strand of each of the two homologous chromatids - Branch migration occurs as the junction between DNA of different helices moves laterally - A junction is formed between the invading DNA and the existing DNA of the chromatid

Which changes can cause a frameshift mutation?

A base deletion A base addition

Which of the following base changes is a transition mutation?

A to G

Which of these bases is most susceptible to oxidative DNA damage?

Guanine

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

Point

Which of these are used by cells to limit the harmful effects of reactive oxygen species?

Superoxide dismutase Catalase Vitamin C

The rare enol form of thymine pairs with the ______.

common keto form of guanine

A double-stranded piece of DNA that has completed homologous recombination may contain a ____ region that contains base mismatches.

heteroduplex

Small sequence differences between homologous chromosomes may cause a recombinant chromosome to have a region with base mismatches, known as a ______.

heteroduplex

The process by which chromosomes exchange similar or identical DNA segments during meiosis is called ______.

homologous recombination

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

oxidative stress

Guanine is commonly ______.

oxidized to 8-oxoguanine

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

tautomeric shift

Which of the following bases is produced by the deamination of 5-methylcytosine?

thymine

Which of the following is least likely to occur as a result of a double-strand break?

Duplications

Which process leads to a new combination of alleles in the chromosomal products?

Homologous recombination during meiosis

The rare imino form of cytosine pairs with the common amino form of

adenine

A mutagen is a(n) ______.

agent that causes mutations

What type of mutations involve a change from a normal codon to a stop codon? Multiple choice question.

nonsense

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

point

Which of these point mutations would likely have an inhibitory effect on protein function?

Frameshift, Missense, Nonsense

The movement of a Holliday junction that causes one strand in a DNA helix to be swapped with a strand in another DNA helix is called ______.

branch migration

The following are steps in the nucleotide excision repair (NER) system. Place them in order, starting with the earliest on top.

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 UvrC are released 6. DNA polymerase fills the gap and DNA ligase seals the region.

What is responsible for silent mutations?

The degeneracy of the genetic code

A silent mutation is a mutation that results in no ______.

change to the amino acid sequence of the polypeptide

Reactive oxygen species (ROS) are ______.

products of oxygen metabolism in all aerobic organisms

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.

The amino form is the common stable form of which bases?

Adenine Cytosine

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

Which of these represents the correct order of steps during a typical DNA repair system?

Detection → Removal → Replication

The first proposal for a set of steps at the molecular level that lead to homologous recombination is called the ____ model.

Holliday

Nucleotide excision repair (NER) is the main system used in the repair of ______.

bulky, helix distorting lesions

Which of these bases is most readily deaminated?

cytosine

The removal of an amino group from a base is called

deamination

This figure highlights the process of ______.

deamination

Silent mutations are possible because the genetic code is ______. Multiple choice question.

degenerate

The removal of a purine from DNA is called

depurination

Mutations that remove an adenine or guanine from the DNA are known as ______.

depurinations

Changes to DNA structure caused by reactive oxygen species (ROS) are termed

oxidative DNA damage

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

reactive oxygen

Oxidative DNA damage refers to changes in DNA structure that are caused by ______.

reactive oxygen species

Bases which exist in keto and enol or amino and imino forms are best described as ______.

tautomers

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 oxidized form of guanine, 8-oxoguanine, can produce a _____ mutation.

transversion

Assume a tautomeric shift occurred, which was followed by two rounds of DNA replication. If the mutation is not repaired, what would be the result?

AT to GC mutation in one of the four daughter molecules

Which model includes formation of a junction between DNA strands from different but homologous helices, including migration of that junction to produce heteroduplex DNA?

Holliday Model

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

Cells can prevent the buildup of reactive oxygen species by using enzymes such catalase and superoxide

dismutase

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

double strand

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

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 tautomeric shift is a ______.

temporary change in base structure

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

wild type

A mutation in a gene that causes an amino acid change in the encoded protein is called a ______ mutation.

missense

Errors in DNA replication are examples of ______ mutations, while mutations caused by ultraviolet light are ______ mutations.

spontaneous ; induced