Unit 4 - Chapter 19, Chapter 20
Which of the following are base analogs?
2-aminopurine 5-bromouracil
In recombination, what is the process that synthesizes small stretches of DNA to replace those removed by strand degradation?
DNA gap repair synthesis
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
Which of the following are examples of ionizing radiation?
X-rays and gamma rays
What is a cloning vector?
a molecule that carries the DNA to be cloned
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
In gene cloning, what is the vector?
a small DNA molecule that can replicate independently within a host cell
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
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
Base analogs induce mutations by ______.
being incorporated instead of normal bases during DNA replication
Physical mutagens include ______.
both X-rays and UV light
The region where two chromosome pieces break and re-attach to other chromosome pieces is called a chromosomal
breakpoint
Which of the following are examples of base pair mismatches?
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
The removal of an amino group from a base is called
deamination
Which of the following are forms of tautomers?
enol imino keto amino
Which of these are examples of alkylating agents?
ethyl methanesulfonate nitrogen mustard
True or false: During homologous recombination repair, the two broken ends of DNA are pieced back together.
false
Acridine dyes cause ______ mutations.
frameshift
The Ames test assays whether an agent causes ______.
gene mutations
A mutant allele is best defined as an allele that ______.
has a different DNA sequence from the wild-type
The process by which chromosomes exchange similar or identical DNA segments during meiosis is called ______.
homologous recombination
Double-strand breaks are typically repaired by which of the following?
homologous recombination repair nonhomologous end joining
The two main mechanisms used to repair DNA double-strand breaks are ____ recombination repair and ____ end joining.
homologous; nonhomologous
What is the term that describes a cell that contains a DNA cloning vector?
host cell
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
Gamma rays and X-rays are examples of a type of radiation called ____ radiation
ionizing
Alkylating agents covalently attach ____ or ____ groups to DNA bases, and this disrupt their normal base pairing properties
methyl or ethyl
Gene conversion occurs by the action of ______.
mismatch repair DNA gap repair synthesis
A mutation in a gene that causes an amino acid change in the encoded protein is called a ______ mutation.
missense
A base substitution in DNA that ultimately leads to a change in the encoded amino acid is called a(n) ____ mutation
missensed
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
Which of these are examples of mutagens?
nitrous acid nitrogen mustard 2-aminopurine 5-bromouracil
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
Changes to DNA structure caused by reactive oxygen species (ROS) are termed
oxidative DNA damage
The process by which thymine dimers are directly repaired with the help of light is called
photoreactivation
In addition to the DNA strands of the chromosomes involved in homologous recombination, the multiple steps in the pathway require the action of
protein catalysts
The multiple steps of homologous recombination, including strand breakage and rejoining, require the action of ______.
protein catalysts
Oxidative DNA damage refers to changes in DNA structure that are caused by ______.
reactive oxygen species
____ DNA technology uses in vitro molecular techniques that combine DNA fragments to produce novel arrangements.
recombinant
DNA N-glycosylases participate in the base excision repair (BER) system. These enzymes ______.
remove an abnormal base
If a heteroduplex includes a region with an allelic difference, the cell will ______.
repair the mismatch to either the dominant or recessive allele
A mutation that does not change the amino acid sequence of a polypeptide is known as a(n) ____ mutation
silent
Bases which exist in keto and enol or amino and imino forms are best described as ______.
tautomers
Which of these tests is used to evaluate the mutagenicity of an agent?
the Ames test
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
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 mutation nitrous acid changes cytosine to ____ and adenine to _____
uracil; hypoxanthine
A breakpoint refers to the region ______.
where two chromosome pieces break and rejoin with other chromosome pieces
Translesion DNA polymerases incorporate wrong nucleotides with a frequency of approximately _____, which is ______ than the error rate for replicative DNA polymerases.
10 -2; higher
A mutagen is a(n) ______.
agent that causes mutations
Base analogs include 2-____ and 5-____.
aminopurine; bromouracil
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
Which of these represents the correct order of steps during a typical DNA repair system?
detection -> removal -> replication
Photoreactivation is a repair mechanism that can ______ a thymine dimer in the ______ of light.
directly split; presence
Alkylating agents cause mutations by ______.
disrupting the normal pairing between nucleotides within the DNA
Ionizing radiation produces chemically reactive molecules known as ____ ____. These are mutagenic because they alter the structure of DNA.
free radicals
A situation in which one allele is changed to the allele found on the homologous chromosome is called ______.
gene conversion
An unexpected observation of the outcome of meiosis in the fungus Neurospora, in which the ratio of orange to white products was 6:2 instead of 4:4, demonstrated which process?
gene conversion
The mutation rate is commonly expressed as the number of new mutations in a given ______.
gene per cell generation
Cells that give rise to the gametes such as eggs and sperm are called
germ line
DNA gap repair synthesis
restores the stretches of DNA removed by strand degradation at the initiation of recomination
Which of the following terms is associated with ionizing energy?
short wavelength high energy gamma rays
DNA N-glycosylases are enzymes involved in ______.
base excision repair
Nucleotide excision repair (NER) is the main system used in the repair of ______.
bulky, helix distorting lesions
True or false: Chromosomal DNA is a common source of cloned DNA.
true
Acridine dyes induce mutations by ______.
inserting themselves between adjacent bases and thus distorting DNA structure
A change of one base for another is described as a base ____ mutation
substitution
This figure best illustrates what type of mutation?
base substitution
Nitrous acid is a mutagen that acts via the process of ______.
deamination
What is recombinant DNA technology?
the production of new arrangements of DNA
The term germ line is used to describe the ______.
cells that produce sperm and eggs
What is the purpose of gene cloning?
to produce many copies of a DNA molecule of interest
You would ____ a gene to make many copies of that gene
clone
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
Ionizing radiation is characterized by ______.
short wavelength and high energy
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
How does ionizing radiation cause mutations?
it forms free radicals that can introduce breaks into the DNA molecule
This figure shows an example of a(n) ____ ____ mutation Illustration shows single panel. When there is no mutation then transport can occur. After first mutation, the functioning of proteins gets disrupted and a suppressor mutation affects the same protein restores function. In this example, the second mutation restores the function and hence, gtransport occurs. this is an example of intragenic suppressor.
intragenic suppressor
A silent mutation is a mutation that results in no ______.
change to the amino acid sequence of the polypeptide
A particular gene to be cloned is often isolated from ______.
chromosomal DNA
Trinucleotide repeat expansions are repeated sequences of three nucleotide bases which ______.
increase generation after generation
The first proposal for a set of steps at the molecular level that lead to homologous recombination is called the ____ model.
Holliday
The phenomenon in which a repeated sequence of three nucleotide bases increases in number generation after generation is called
trinucleotide repeat expanion
The red arrow in this figure points to a(n) Illustration shows two strands of DNA one with 5'-3' end and other with 3'-5' end. Nitrogenous bases are complementary to each other. The arrow shows apurinic site in which a purine is removed by the process of depurination.
apurinic site
This figure highlights the process of ______. Illustration shows a carbon ringed structure attached to methyl group, oxygen and amino group. Nitrogen is attached to sugar. this is 5-methylcytosine which is deaminated by removal of amino group on addition of water. the amino group is replaced by oxygen and forms uracil. This process is known as deamination.
deamination
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
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 removal of a purine from DNA is called
depurination
Mutations that remove an adenine or guanine from the DNA are known as ______.
depurinations
An agent that can change DNA structure and cause mutations is known as a(n)
mutagen
A small circular DNA molecule that is often used as a vector in gene cloning is called a(n)
plasmid
Alkylating agents include nitrogen ____ and ethyl _____
mustard; methanesulfonate
This figure shows a technique known as First, individual bacteria cells were plated onto growth media. The cells were allowed to divide during an overnight incubation, during which time random mutations may occur. During the overnight incubation, bacterial colonies formed. This plate is called the master plate. Some colonies on the master plate do not have mutations. Other colonies contain some cells which have a random mutation that gives resistance to T1. A velvet cloth wrapped around a clyinder was pressed onto the master plate, and gently lifted to obtain a replica of each bacterial colony. The replica was presssed onto 2 secondary plates that contain T1 phage. The plates were incubated overnight to allow growth of mutant cells. Nonmutant cells were lysed and killed on the T1 plates.
replica plating
Base excision repair (BER) is the main system used in the repair of ______.
abnormal bases
Translesion DNA polymerases are ______ accurate and ______ sensitive to geometric distortions in DNA than replicative DNA polymerases.
less; less
Errors in DNA replication are examples of ______ mutations, while mutations caused by ultraviolet light are ______ mutations.
spontaneous; induced