Chapter 8
____ is an agent that induces changes in DNA
mutagen
DNA in the environment that is not contained within a cell or virus is called ____ DNA
naked
free DNA found in the environment is called ____ DNA
naked
x rays can cause which types of damage to a DNA molecule
nucleobase alterations; singe stranded breaks; double stranded breaks
chemical mutagens that modify ____ increase the odds of incorrect nucleotide incorporation during DNA replication
nucleobases
a ____ is a virus that infects bacteria
phage
______ (aka light repair) involves enzymes that use the energy of visible light to remove the covalent bonds that have formed between the thymines
photoreactivation
the repair of thymine dimers by enzymes that break the covalent bonds between the dimers is called _____ repair.
photoreactivation
small, usually circular pieces of DNA that contain their own origin of replication are called _____.
plasmids
recognition and repair of errors in nucleotide incorporation by DNA polymerase is called ______
proofreading
bacteriophages can consist of:
DNA genome, protein coat, RNA genome
_____ transfer is the transfer of DNA from a source other than the parent organisms
Horizontal gene transfer
cells hat have the ability to take up DNA from the environment are called ___ cells
competent
____ refers to DNA transfer requiring cell to cell contact
conjugation
what are some methods of the introduction of new genetic information into bacteria?
conjugation, transduction, and transformation
_____ involves that transfer of DNA via bacteriophages
transduction
what transfers DNA from donor to recipient via a bacteriophage?
transduction
in inerstion sequences, the ____ gene is flanked by ____ repeats
transposase; inverted
"jumping genes" or ____ can lead to changes in genotype within a cell or between cells.
transposons
sequences of DNA that can move to new positions within the genome of a single cell are called ______
transposons
what types of radiation are mutagenic?
ultraviolet rays; x-rays
______ transfer is the transfer of DNA from parent organisms during reproduction
vertical gene transfer
an auxotroph can be isolated from a prototrophic parent strain by ____ selection
indirect
mutations that are caused by external influences such as radiation or chemicals are called ___ mutations
induced
____ is the change of a mutated genetic sequence back to its original non-mutated form.
reversion
most transposons contain ____ terminators
transcriptional
ultraviolet radiation causes a very specific type of DNA damage called ______
thymine dimers
protection against the toxic effects of antimicrobial compounds or heavy metals is often found to be encoded on ____ plasmids
R
_____ repair is activated by extensive DNA damage and uses polymerases that lack proofreading ability ultimately resulting in mutations.
SOS
extensively damaged DNA activates the ____ repair mechanism, which cannot always determine the correct nucleotide sequence, thus resulting in mutations resulting from the repair process itself.
SOS
T/F plasmids are small, usually, circular pieces of DNA that contain their own origin of replication
True
______ repair (aka dark repair) involves enzymes that make single stranded cuts that flank the region containing the thymine dimer to remove it.
excision
proteins that remove thymine dimers without light are termed _____ repair enzymes.
excision
______ agents increase the rate of _____ mutations by inserting themselves between adjacent base pairs in a DNA strand.
intercalating ; frameshift
chemical mutagens that squeeze between base pairs and induce frameshift mutations are called ______
intercalating agents
what are some of the components of simplest transposon, an insertion sequence.
inverted repeats, transposase gene
the enzymes of the mismatch DNA repair mechanism distinguish between the template strand and the newly synthesized strand by the presence of a ____ group on certain nucleobases of the template strand.
methyl
sometimes the proofreading function of DNA polymerase misses errors in nucleotide incorporation. the errors are usually fixed by a mechanism called _____ repair
mismatch
a base substitution that results in a codon that still codes for the wild type amino acid is called a _____ mutation
silent
random genetic changes that occur as a result of natural cellular processes are called ____ mutations
spontaneous
base ___ mutation occur when incorrect nucleotide is incorporated in place of another during DNA synthesis
substitution
_____ ______ are molecules whose structure resembles that of nucleobases and can be mistakenly incorporated into DNA
base analogs
the repair of thymine dimers by enzymes that make single stranded cuts that flank both sides of the thymine dimer is called ____ repair
excision
T/F a point mutation always leads to a shift of the reading frame from the point of mutation downstream
false
T/F plasmids are insertion sequences that can lead to changes in genotype within a cell or between cells.
false
T/F ultraviolet rays are chemical mutagens
false
____ mutation results from an insertion or deletion of nucleotides, leading to a shift of the reading frame from the point of mutation downstream.
frameshift
______ mutation results from an insertion or deletion of nucleotides, leading to a shift of the reading frame from the point of mutation down
frameshift
what are possible outcomes of a base substitutiions?
missense mutation, silent mutation, and nonsense
in bacterial conjugation, F+ donor cells are high frequency recombinant (hfr) cells when the F____ is integrated into the chromosome
plasmid
small, usually circular pieces of DNA that contain their own origin of replication are called ____-
plasmids
______ mutations are genetic changes caused by factors from outside of the cell such as radiation or chemicals
induced
the return of a gene from a mutated state to its original, non-mutated state is called a _____
reversion
the distortion of DNA by thymine dimers directly blocks which of the following cellular processes?
transcription;replication