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