Micro Biology ch.16

Point mutations that change the nucleotide sequence of a codon but do not change the amino acid encoded by that codon are called mutations.

silent

Which two of these missense mutations would be likely to have a significant effect on the function of the protein encoded by the mutated gene?

substitution of an amino acid located at the active site of an enzyme replacement of a nonpolar amino acid with a polar amino acid

Spontaneous mutations can occur when a nitrogenous base shifts to a different isomer, also called a(n) ____.

tautomeric form

DNA-modifying agents induce DNA mutations by _____.

changing the chemical structure of a base

Base analogues, DNA-modifying agents, and intercalating agents are three types of mutagens.

chemical

A mutant strain of E. coli that grows normally at 30°C, but dies at 40°C, is a(n)_________ mutant. Multiple choice question.

conditional

Mutations that are expressed only under certain environmental conditions are called mutations.

conditional

Adenine can exist in a rare imino form that can base pair with the abnormal partner ____. Multiple choice question.

cytosine

Possible causes of spontaneous mutation include

errors in DNA replication transposons spontaneous lesions in DNA

A suppressor mutation that occurs in a different gene from the first mutation is called a(n) suppressor mutation.

extragenic

A mutation that leads to a change from wild type to a mutant form is called a(n) mutation.

forward

Silent, missense, nonsense, and frameshift are all common types of mutations.

forward

Mutations that arise from the insertion or deletion of base pairs within the coding region of a gene are specifically called mutations.

frameshift

thymine in the enol form

g

Base analogues induce DNA mutations by _____. Multiple choice question.

incorporating into the growing DNA chain

Chemical mutagens that are planar and insert themselves between stacked bases of the DNA helix are called______,agents.

intercalating

Select three examples of chemical mutagens.

intercalating agents base analogs DNA-modifying agents

A suppressor mutation that occurs within the same gene as the first mutation is called a(n) suppressor mutation.

intragenic

Once a frameshift mutation has occurred in a gene, a second, nearby frameshift mutation that restores the original reading frame is called a(n) ______ suppressor mutation. Multiple choice question.

intragenic

Point mutations that involve a single base substitution and result in a change to the amino acid encoded are called mutations. These mutations may or may not have a significant impact on the protein structure.

missense

Which of these types of point mutation is most likely to drive evolution because they are not lethal and remain in the gene pool?

missense

A point mutation that involves a single base substitution and results in a change to the amino acid encoded by that codon is specifically called a _____.

missense mutation

Transition mutations, which result in substitution of the alternate purine for the original purine, or the alternate pyrimidine for the original pyrimidine, are __________ common than transversion mutations. Multiple choice question.

more

A wild-type chemoorganotroph able to grow on a minimal medium containing only salts and a carbon source is known as a(n) . These wild-type stains may give rise to mutants incapable of survival without additional nutrients, like a particular amino acid.

prototroph

A mutant that can survive exposure to some pathogen, chemical, or antibiotic, is a(n) mutant.

resistance

Which two of these descriptions apply to auxotrophs? Multiple select question.

They have a conditional phenotype. They are unable to grow on medium lacking a particular molecule, where the wild-type strain could grow.

How do intercalating agents induce DNA mutations?

They insert between stacked bases of the helix

Which two statements correctly describe missense mutations?

They involve a single base substitution that changes a codon for one amino acid into another. Effects range from no change to complete loss of normal gene function.

Which two of these statements are correct about frameshift mutations?

They usually yield mutant phenotypes. They usually result in the synthesis of nonfunctional proteins.

A second mutation that occurs at a different site from the first mutation, and which returns the mutant back to the wild-type phenotype, is a(n) mutation.

reversion

Frameshift mutations often lead to the synthesis of nonfunctional proteins. However, the effects of these mutations would likely be reduced in which three of these scenarios?

A second frameshift mutation occurs shortly downstream from the first, restoring the reading frame. The frameshift occurs near the end of the gene. An intragenic suppressor mutation occurs.

Which three types of mutations are classified as reversion mutations?

A second mutation creates a codon that replaces the wild type amino acid with a similar amino acid. A second mutation that creates a new codon that codes for the wild type amino acid. A second mutation that restores the original wild-type sequence.

Which three of these statements are correct about nonsense mutations?

By definition, they always produce stop codons. They cause the early termination of translation. Effects range from mild to complete loss of normal gene function.

Mutagens that change the chemical structure of a base, thereby altering its base-pairing specificity, are called _____.

DNA-modifying agents

Which example of a missense mutation in a protein-encoding gene would most likely be a neutral mutation?

Replacement of a polar amino acid with another polar amino acid at the protein's surface

Why are transversion mutations more rare than transition mutations?

There are steric problems with pairing purines with purines.

Which of the following is depicted in the diagram? Multiple choice question.

Slippage leading to a deletion

The diagram shows which of the following?

Slippage leading to an insertion

Mutations that result from the activity of mobile genetic elements called transposons are considered to be which type of mutations?

Spontaneous

A suppressor mutation, which returns a mutant back to its wild-type phenotype, occurs at ____________ the first mutation.

a different site from

Cytosine can exist in a rare imino form that can base pair with the abnormal partner ____.

adenine

Chemical mutagens that are structurally similar to normal DNA nucleotides, which therefore can be incorporated into the growing DNA chain, are called base .

analogues

Adenine or guanine nucleotides can lose their base, resulting in a(n) ______.

apurinic site

Cytosine or thymine nucleotides can lose their base, resulting in a(n) ______.

apyrimidinic site

An organism with a mutation that affects its ability to synthesize a biochemical essential for its growth is known as a(n) .

auxotrophs

Match each type of mutation with the appropriate example. auxotroph---> conditional---> morphological--> resistance---->

mutant cannot synthesize an essential molecule such as an amino acid phenotype is only affected at high temperatures mutation affects the appearance of colonies resistance matches mutant is not affected by a particular pathogen or chemical

The general term for heritable changes in DNA sequence is

mutation

A missense mutation that has little to no effect on the activity of a gene product is called a(n) mutation.

neutral

A tautomeric form is an isomer of a nucleotide in which the _____ is changed.

nitrogenous base

Point mutations that result in a new stop codon are called mutations.

nonsense

The type of mutation that affects only a single base pair at a given DNA location is called a(n)_______ mutation.

point

A mutation that caused the codon CGU to change to CGC, which does not affect the amino acid encoded, could be described by which two of these terms? Multiple select question.

point silent

Missense mutations provide variation within a population and drive evolution because _____. Multiple choice question.

they are not lethal and remain in the population gene pool

Guanine can exist in a rare enol form that can base pair with the abnormal partner ____.

thymine

Nucleotide substitutions that result in purine for purine or pyrimidine for pyrimidine mutations are known as mutations.

transition

Nucleotide substitutions that result in purine for pyrimidine, or pyrimidine for purine mutations, are known as mutations.

transversion

True or false: Lethal mutants can be recovered only if they are conditional mutants.

true

The most prevalent form of a gene, and its associated phenotype, is called the type.

wild

The most prevalent form of a gene, and its associated phenotype, is called the _______.

wild type

A mutation that caused the codon CGU to change to CGC, which does not affect the amino acid encoded, could be described by which two of these terms?

silent point

The diagram illustrates the genetic changes that result from different types of mutations. Match the letter of each type of mutation with the appropriate name. A----> B-----> c-----> D----->

silent mutation missense mutation nonsense mutation frameshift mutation