week 11 part 2 chapter 19
represents the correct order of steps during a typical DNA repair system?
Detection → Removal → Replication
Digests the nonmethylated strand
Exonuclease
Makes a cut in a nonmethylated strand
MutH
acts as a linker that helps loop the DNA
MutL
Detects the mismatch
MutS
Separates strands at the cleavage site
MutU
Thymine dimers are typically caused by ______.
UV light
a base substitution in DNA that ultimately leads to a change in the encoded amino acid is called _
_missense 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 analogs
Adenine on parent strand and Cytosine on daughter strand Cytosine on parent strand and Thymine on daughter strand Cytosine on parent strand and Adenine on daughter strand are exampls of
base pair mismatch
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
Base analogs induce mutations by ______.
being incorporated instead of normal bases during DNA replication
the embryo carries a germ-line mutation, other carries a somatic mutation. Which embryo will be able to pass this mutation on to future progeny
germ-line embryo
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. Only one of the two alleles is likely to be mutated so only half the gametes are expected to contain the mutated allele.
half, none
alkylating agents covalently attach ____ or _____ groups to DNA bases, and thus disrupt their normal base pairing properties
methyl, ethyl
a mutation in a gene that causes an amino acid change in the encoded protein is called
missense
a mutation in a gene that causes an amino acid change in the encoded protein is called a
missense mutation
The probability that a gene will be altered by a new mutation is referred to as the
mutation rate
a mutation that results in a premature termination of the synthesis of a polypeptide is called
nonsense
which type of mutation involves a change from a normal codon to a stop codon
nonsense mutation
Translesion synthesis refers to the ______.
replication of a template strand that contains DNA damage
Errors in DNA replication are examples of ______ mutations, while mutations caused by ultraviolet light are ______ mutations.
spontaneous, induced
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
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
In the mismatch repair system, the proteins ______ form a complex that activates _____, which is already bound to a ______ DNA site.
MutS/MutL ; MutH ; hemimethylated
what can cause a frameshift mutation
a nucleotide addition or deletion
Which of these tests is used to evaluate the mutagenicity of an agent?
ames test
Nucleotide excision repair (NER) is the main system used in the repair of ______.
bulky, helix distorting lesions
what is responsible for silent mutation
degeneracy of genetic code
silent mutations are possible because the genetic code is
degenerate
Alkylating agents cause mutations by _____
disrupting the normal pairing between nucleotides within the DNA
a position effect can alter gene expression in cases when the gene is moved from a less condensed or _____ chromosome, where it is active, to a very highly condensed, or ______ chromosome, where it expression may be turned off
euchromatic, heterochromatic
the addition or deletion of a number of bases that is not a multiple of three causes a
frameshift mutation
The Ames test assays whether an agent causes ______.
gene mutations
The two main mechanisms used to repair DNA double-strand breaks are
homologous recombination repair, nonhomologous end joining
The mutation rate is commonly expressed as the number of new mutations ______.
in a given gene per cell generation
Trinucleotide repeat expansions are repeated sequences of three bases which ______.
increase in number from generation to generation
Some errors create bulky distortions of the double helix. These errors are removed primarily by a DNA repair system called NER, which stands for
nucleotide excision repair
a suppressor mutation is so named because it suppresses the
phenotypic effect of another mutation
The enzyme that can recognize thymine dimers and split them is called
photolyase
______ mutation refers to a mutation in which just one base is changed within the DNA sequence
point
a change in a single base pair in the genetic material is known as
point mutation
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.
suppressor
a temporary change in base structure due to movement of hydrogen atoms is called
tautomeric shift
A tautomeric shift is a ______.
temporary change in base structure
Ultraviolet light causes the formation of crosslinked ____ ____ in DNA
thymine (pyrimidine) dimers
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
Most DNA repair systems involve three major steps: detection of the error, removal of the abnormality, and its replacement with normal DNA.
true
Down promoter mutations decrease the affinity of transcription factors to the promoter. Up promoter mutations cause the promoter sequence to be more like the consensus sequence
true about promoter mutations
