Genetics- Chapter 18

Gene Mutations & DNA Repair

A heritable change in genetic information

Mutation

_________ are the source of all genetic variation

Mutations

_________ are the raw material of evolution

Mutations

A _______ mutation is one that arises in somatic cells and do not give rise to gametes

Somatic

A _________ mutation is a mutation in a germ-line cell

Germ-line

True or False:

Germ-line mutations are more common than somatic mutations

False

A mutation that affects a single gene or locus

Gene mutation

A mutation that affects the number or structure of chromosomes

Chromosome mutation

The simplest type of gene mutation is a ____ substitution

Base

A mutation in which a single pair of bases in DNA is altered

Base substitution

There are two types of base substitution:

• __________- base substitution in which a purine is replaced by a different purine or a pyrimidine is replaced by a different pyrimidine

• ____________- base substitution in which a purine is replaced by a pyrimidine or vice versa

Transition; transversion

A mutation in which one or more nucleotide pairs are added to a DNA sequence

Insertion

A mutation in which one or more nucleotides are deleted from a DNA sequence; aka indels

Deletion

A mutation that alters the reading frame of a gene

Frameshift mutation

_________ nucleotide repeats are a type of mutation in which the number of copies of a set of nucleotides increases in succeeding generations

Expanding

A _______ mutation is a mutation in which a wild type phenotype is converted to the mutant phenotype

Forward

A _______ mutation is a mutation in which the mutant phenotype is converted to the wild-type phenotype

Reverse

A ________ mutation is a mutation in which a base substitution results in a different amino acid in the protein encoded

Missense

A ________ mutation is a mutation that changes a sense codon into a stop codon

Nonsense

A ______ mutation causes a change in the nucleotide sequence of DNA that does not alter the amino acid sequence of a protein

Silent

True or False:

Some silent mutations have phenotypic effects

True

A _______ mutation is a mutation that changes the amino acid sequence of a protein but does not alter the function of the protein

Neutral

A ____-__-________ mutation causes the complete or partial absence of normal function

Loss of function

A ____-__-________ mutation causes the cell to produce a protein or gene product whose function is not normally present

Gain of function

A ___________ mutation is expressed only under certain conditions

Conditional

A ______ mutation causes premature death

Lethal

Base substitutions can cause a ________, nonsense, or ______ mutation

Missense; silent

A __________ mutation hides or suppresses the effect of another mutation

Suppressor

An __________ suppressor mutation is a suppressor mutation that occurs in the same gene as the mutation that it suppresses

Intragenic

An __________ suppressor mutation is a suppressor mutation that occurs in a gene other than the one bearing the original mutation that it suppresses

Intergenic

The frequency at which a wildtype allele changes into a mutant allele

Mutation rate

Mutation rate =

mutated progeny/total progeny

An ________ mutation is a process by which a specific environment induces mutations that enable organisms to adapt to that environment

Adaptive

A ___________ mutation arises from natural changes in DNA structure or from errors in replication

Spontaneous

An _______ mutation results from environmental agents, such as chemicals or radiation

Induced

True or False:

Replicated errors do not lead to permanent mutations

False

The loss of a purine base from a nucleotide

Depurination

The loss of an amino group from a base

Deamination

Any environmental agent that significantly increases the rate of mutation above the spontaneous rate

Mutagen

A chemical with a structure that is similar to that of any of the 4 standard bases is known as a base ______

Analog

True or False:

DNA polymerases can not distinguish the analogs form the standard bases

True

Alkylating agents donate _____ groups to nucleotide bases

Alkyl

Hydroxylamine adds a ________ group to cytosine

Hydroxyl

Oxidative radicals damage ___ and induce _________

DNA; mutations

An _____________ agent is a molecule that may become sandwiched between adjacent bases in DNA, which distorts the three-dimensional structure of the DNA helix and causing single-nucleotide insertions and deletions in replication

Intercalating

Intercalating agents often produce __________ mutations

Frameshift

The ___ system is a system of proteins and enzymes that allows a bacterial cell to replicate its DNA in the presence of a distortion in DNA structure

SOS

What test is used to evaluate the potential of chemicals to cause cancer?

Ames test

Cancer and mutations result from damage to ___

DNA

The mismatch repair system fixes ___________ errors

Replication

Mismatch repair distinguishes between old and new strands of DNA on the basis of methyl groups on the ___ strand

Old

______ repair is a method of DNA repair in which modified bases are changed back into their original structures

Direct

____ excision repair is a method of DNA repair that first excises modifies baes and then replaces the entire nucleotide

Base

__________ excision repair is a method of DNA repair that removes bulky DNA lesions and other types of DNA damage

Nucleotide

An enzyme that repairs pyrimidine dimers in bacteria

Photolyase

True or False:

A conditional mutation affects the phenotype under all conditions

False

A non-replicative __________ is a DNA sequence that moves throughout the genome by excision and insertin

Transposon

In gel electrophoresis, _______ pieces of genetic material move faster and a ______ band means more genetic material is present

Smaller; larger

Xeroderma pigmentosum occurs as a result of mutations in the genes for DNA ______ systems

Repair

What did Barbara McClintock discover?

Transposons

True or False:

Transposable elements can insert themselves into other genes and disrupt their function

True

UV light produces pyrimidine ______ in DNA molecules

Dimers