MCB4403 - Chp 7 Exam
Study Guide
7.1 Discuss the evidence that led researchers to identify DNA as the genetic material of
cellular organisms. - ANSWER - Oswald Avery, and colleagues discovered that they
could kill a mouse that had live but harmless (avirulent) streptococcus pneumonia, plus
dead cells from a virulent strain of bacteria.
- the transforming agent is DNA.
-also coincidentally discovered the first of several mechanisms of horizontal gene
transfer between microbes.
What is transformation? - ANSWER The internalization of free DNA from the environment
into bacterial cells.
What do viruses such as influenza and SARS-CoV-2 use for their genetic material? -
ANSWER RNA
What key piece of evidence indicates that DNA, rather than protein, is the cellular
genetic material?
A. DNA from dead cells of a virulent strain of Streptococcus pneumoniae can turn an
avirulent strain into a virulent one.
B. Tracking radiolabeled nitrogen atoms within the phage T2 showed that only these
atoms, present in DNA but absent from proteins, entered a host bacterium during
infection
C. There are far more variants of amino acids than nucleic acids.
D. Proteins can be found in chromosomes - ANSWER A. DNA from dead cells of a
virulent strain of Streptococcus pneumoniae can turn an avirulent strain into a virulent
one.
Further analysis revealed DNA as the transforming agent in one of the earliest examples
of horizontal gene transfer between microbes.
What is a dimer? - ANSWER a pair of subunits
What is denaturation? - ANSWER to lose secondary and tertiary structure in a protein or
nucleic acid because of high temperature or chemical treatment.
More energy is required to break three H-bonds of a GC pair than the two H-bonds of an
AT base pair.
, What is hybridization? - ANSWER To form
The annealing of a nucleic acid strand with another nucleic acid strand containing a
complementary sequence of bases. The binding of one nucleic acid strand with a
complementary strand.
What is a hairpin and when in RNA is it formed? - ANSWER -a region that loops back and
forms a "hair pin" structure.
-Form when complementary nucleotide sequences within the primary RNA sequence
bends back and hybridizes.
What is the nucleoid region? - ANSWER The looped coils of bacterial chromosomes
What are topoisomerases? - ANSWER -regulate super coils
An enzyme that can change the supercoiling of DNA
-helps maintain proper DNA supercoiling levels.
What are the two types of topoisomerases? - ANSWER Type I and Type II
Type I: are typically single proteins that cleave only one strand of a double helix
-relieve or unwind supercoils, the enzyme passes the intact strand through the break
and re-ligate (reconnect) the strand, reintroducing a helical turn.
Type II: have multiple subunits that cleave both strands of a DNA molecule.
-DNA gyrase introduce negative supercoils in DNA which is important during DNA
replication
Which antibiotic targets topoisomerases? - ANSWER quinolone - it inhibits DNA
synthesis by targeting bacterial topoisomerases such as DNA gyrase
-does not target eukaryotic topoisomerases.
What are common targets for antibiotics? - ANSWER enzymes that make or manage
bacterial DNA.
Negative supercoiling of the DNA is ________.
A. performed by DNA gyrase
B. absent in the nucleoids of bacteria
C. harmful to transcription because the DNA is overwound
D. performed by topoisomerase IV - ANSWER A. performed by DNA gyrase
Gyrase is a tetrameric complex that uses ATP to introduce a double-stranded break to
unwind the DNA helix.
Study Guide
7.1 Discuss the evidence that led researchers to identify DNA as the genetic material of
cellular organisms. - ANSWER - Oswald Avery, and colleagues discovered that they
could kill a mouse that had live but harmless (avirulent) streptococcus pneumonia, plus
dead cells from a virulent strain of bacteria.
- the transforming agent is DNA.
-also coincidentally discovered the first of several mechanisms of horizontal gene
transfer between microbes.
What is transformation? - ANSWER The internalization of free DNA from the environment
into bacterial cells.
What do viruses such as influenza and SARS-CoV-2 use for their genetic material? -
ANSWER RNA
What key piece of evidence indicates that DNA, rather than protein, is the cellular
genetic material?
A. DNA from dead cells of a virulent strain of Streptococcus pneumoniae can turn an
avirulent strain into a virulent one.
B. Tracking radiolabeled nitrogen atoms within the phage T2 showed that only these
atoms, present in DNA but absent from proteins, entered a host bacterium during
infection
C. There are far more variants of amino acids than nucleic acids.
D. Proteins can be found in chromosomes - ANSWER A. DNA from dead cells of a
virulent strain of Streptococcus pneumoniae can turn an avirulent strain into a virulent
one.
Further analysis revealed DNA as the transforming agent in one of the earliest examples
of horizontal gene transfer between microbes.
What is a dimer? - ANSWER a pair of subunits
What is denaturation? - ANSWER to lose secondary and tertiary structure in a protein or
nucleic acid because of high temperature or chemical treatment.
More energy is required to break three H-bonds of a GC pair than the two H-bonds of an
AT base pair.
, What is hybridization? - ANSWER To form
The annealing of a nucleic acid strand with another nucleic acid strand containing a
complementary sequence of bases. The binding of one nucleic acid strand with a
complementary strand.
What is a hairpin and when in RNA is it formed? - ANSWER -a region that loops back and
forms a "hair pin" structure.
-Form when complementary nucleotide sequences within the primary RNA sequence
bends back and hybridizes.
What is the nucleoid region? - ANSWER The looped coils of bacterial chromosomes
What are topoisomerases? - ANSWER -regulate super coils
An enzyme that can change the supercoiling of DNA
-helps maintain proper DNA supercoiling levels.
What are the two types of topoisomerases? - ANSWER Type I and Type II
Type I: are typically single proteins that cleave only one strand of a double helix
-relieve or unwind supercoils, the enzyme passes the intact strand through the break
and re-ligate (reconnect) the strand, reintroducing a helical turn.
Type II: have multiple subunits that cleave both strands of a DNA molecule.
-DNA gyrase introduce negative supercoils in DNA which is important during DNA
replication
Which antibiotic targets topoisomerases? - ANSWER quinolone - it inhibits DNA
synthesis by targeting bacterial topoisomerases such as DNA gyrase
-does not target eukaryotic topoisomerases.
What are common targets for antibiotics? - ANSWER enzymes that make or manage
bacterial DNA.
Negative supercoiling of the DNA is ________.
A. performed by DNA gyrase
B. absent in the nucleoids of bacteria
C. harmful to transcription because the DNA is overwound
D. performed by topoisomerase IV - ANSWER A. performed by DNA gyrase
Gyrase is a tetrameric complex that uses ATP to introduce a double-stranded break to
unwind the DNA helix.
