Genetics Study Guide

Translesion DNA polymerases have an error rate of about __, which is much ___ than replicative polymerases

10^-3, 10^-2, higher

What is the size of the nucleosome-free region found at the core promoter of active genes?

150 bp

What can cause a frameshift mutation?

A nucleotide addition/deletion

In trinucleotide repeat expansion disorders, when the expansion occurs in the coding sequence of the gene, the repeat sequence is usually

CAG

The cress plant Arabidopsis undergoes vernalization, where flowering in spring requires exposure to colder temperatures during the preceding winter. Which type of modification persisting from winter into spring has been associated with vernalization

Covalent modification of histones associated with specific genes

How does ionizing radiation cause mutations?

It forms free radicals that can introduce breaks into the DNA molecule.

In which of the following ways does 5-bromouracil cause a mutation?

It replaces the base thymine, and can base pair with guanine rather than adenine

What is the effect of a suppressor mutation?

It suppresses the phenotypic effect of another mutation.

Which of the following are forms of tautomers?

Keto Amino Enol Imino

Eukaryotic homologs for which of the following have been found so far?

MutS and MutL

Which pair of proteins is required for nucleotide excision repair (NER)?

UvrC and DNA ligase

What can cause double-strand breaks (DSBs)?

X-rays, gamma rays, reactive oxygen species

Base analogs include 2-________and 5-_____

aminopurine, bromouracil

5-bromouracil is a base Multiple choice question.

analog that changes an AT base pair to a GC base pair.

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

analogs

Some trinucleotide repeat disorders get progressively more severe in future generations. This phenomenon is termed

anticipation

Hot spots are regions of the chromosome that

are more likely to mutate than other regions.

Replica plating is a technique in which

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

Base analogs induce mutations by Multiple choice question.

being incorporated instead of normal bases during DNA replication.

A protein that increases the rate of transcription but does not directly bind to the DNA is called a

coactivator

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 germ-line mutation is one that occurs in

sperm or egg cell

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

spontaneous; induced

A deleterious mutation is best defined as one that decreases the chance of

survival and reproduction

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

tautomeric shift

The term germ line is used to describe

the cells that produce sperm and eggs.

In trinucleotide repeat expansion diseases, the phenomenon of anticipation varies based on the gender of the transmitting parent, suggesting th

there are differences in expansion in oogenesis vs. spermatogenesis.

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

thymine

a is a protein that influences the ability of RNA polymerase to transcribe a given gene

transcription factor

As a result of a diet of royal jelly, queen bees develop differences in _____ when compared with worker bees.

DNA methylation

DNA methylation, chromatin remodeling, covalent histone modification and localization of histone variants are all examples of

Epigenetics

Variation of gene expression that is transmissible and reversible but not related to the variation in the DNA is called

Epigenetics

The bacterium used in the Ames test is Multiple choice question.

Salmonella typhimurium.

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

Superoxide dismutase, vitamin c, catalase

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

In the mismatch repair system, how is the newly-made daughter strand distinguished from the parental strand? Multiple choice question.

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

Physical mutagens include

both X-rays and UV light.

Nucleotide excision repair (NER) is found in Multiple choice question.

both prokaryotes and eukaryotes.

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

breakpoint

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

bulky, helix distorting lesions

Nitrous acid changes the base adenine to hypoxanthine, which pairs with the base ____. This leads to mutations in the newly-synthesized DNA strand during DNA replication.

cytosine

Which of these bases is most readily deaminated?

cytosine

The mutagen nitrous acid changes cytosine to uracil, and adenine to hypoxanthine, through 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 cause mutations by

disrupting the normal pairing between nucleotides within the DNA.

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

double strand

A mutation in a gene may affect the phenotype of the organism in a way that is ______ for its survival. Multiple choice question.

either beneficial, harmful, or neutral

Steroid hormones are synthesized by___ glands and secreted into the bloodstream, ultimately affecting the transcription or expression of genes in target cells

endocrine

True or false: The phenotypic effects of a mutations are either detrimental or neutral.

false

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

frameshift

Acridine dyes cause

frameshift mutations

Gene regulation means that Multiple choice question

gene expression can be controlled so that genes can be expressed at high or low levels.

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

germ-line mutation

Proteins associated with trinucleotide repeat expansion disorders typically contain long tracts of the amino acid

glutamine or gin

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.

half, none

A mutant allele is best defined as an allele that

has a different DNA sequence from the wild type.

The Ames test uses a strain of the bacterium Salmonella typhimurium that is unable to produce the amino acid

histidine

Intercalating agents like acridine dyes induce mutations by

inserting themselves between adjacent bases and thus distorting DNA structure

Proflavin is best described as a(n) Multiple choice question.

intercalating agent

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

intragenic

The restoration of function by a second mutation at a different site in the same gene is known as a(n)

intragenic suppressor

The restoration of function by a second mutation at a different site in the same gene is known as a(n) Multiple choice question.

intragenic supressor

Translesion DNA polymerases are ______ accurate and ______ sensitive to geometric distortions in DNA than replicative DNA polymerases

less ; less

Nonionizing radiation is characterized by

long wavelength and low energy.

When fully methylated DNA is replicated, it is initially hemimethylated. The hemimethylated DNA is recognized by DNA methyltransferase, which makes it fully methylated. This process is called

maintenance methylation.

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

missense mutation

Nitrous acid causes mutations by

modifying bases and thus altering their normal base-pairing properties.

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

mutagens

A silent mutation is a mutation that results in

no change to the amino acid sequence of the polypeptide.

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

nonsense mutation

A change in chromatin confirmation from closed to open often involves the movement of Multiple choice question.

nucleosomes

The proteins UvrA, UvrB, UvrC, and UvrD are required for the DNA repair system called Multiple choice question.

nucleotide excision repair

Changes to DNA structure caused by reactive oxygen species are termed ___ DNA damage

oxidative

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

oxidative stress

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

photolyase

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

point

Reactive oxygen species (ROS) are

products of oxygen metabolism in all aerobic organisms

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

reactive oxygen species.

DNA sequences that are analogous to the operator sites found near bacterial promoters are called ____, or ______ elements

regulatory, control

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

reverse

A chemical agent is being assayed for mutagenicity using the Ames test. This agent would be judged to be a mutagen if the number of bacterial colonies on the test plate is

significantly lower than that of the control plate

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

translesion synthesis

The phenomenon in which a repeated sequence of three bases increases in number generation after generation is called

trinucleotide repeat expansion

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

True or false: The function of regulatory transcription factors is modulated.

true

An enhancer is a DNA element that is bound by a regulatory transcription factor, which leads to

up regulation

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 base cytosine is deaminated to produce the base

uracil

In trinucleotide repeat expansion diseases, the phenomenon of anticipation can vary depending on

which parent the allele was inherited from.

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

wild-type

The mutation rate is commonly expressed as the number of new mutations

in a given gene per cell generation

Which of these are trinucleotide repeat expansion disorders? Multiple select question.

Myotonic muscular dystrophy Huntington disease Fragile X syndrome

In the Ames test for mutagenicity, the control sample contains what?

Rat liver extract + Salmonella bacteria that cannot synthesize histidine

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.

The protein complex that facilitates the interaction between RNA polymerase II and regulatory transcription factors is called

mediator

Alkylating agents covalently attach ___ or _____ groups to DNA bases, and thus disrupt their normal base pairing properties. Correct Answer

methyl or ethyl

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