©SIRJOEL EXAM SOLUTIONS
10/3/2024 9:54 PM
Brock Biology of Microorganisms - Chapter
6 Exam Questions With Correct Answers
Protein-nucleic acid interactions - answer✔these can be site-specific or nonspecific
DNA-binding proteins - answer✔-small molecules that influence that binding of regulatory
proteins to DNA
-most interact with DNA in sequence-specific manner
-specificity provided by interactions between aa side chains and chemical groups on bases and
sugar-phosphate backbone of DNA
-main site for binding is MAJOR GROOVE
inverted repeats - answer✔-useful sequence type
-frequent binding sites for regulatory proteins
-make it easy for protein dimers to form, which can have various uses
domain - answer✔-region of polypeptide with specific structure and function
-in DNA binding, one of these binds to one inverted repeat
-fits in major groove and along backbone
"helix-turn-helix" (structure of DNA-Binding Proteins) - answer✔-(two a-helices connected by a
short 'turn' sequence)
-first helix is recognition helix
-second helix is stabilizing helix
-common in Bacteria (ex. lac and trp repressors in E.coli)
recognition helix - answer✔part of DNA-binding protein that interacts specifically with DNA
, ©SIRJOEL EXAM SOLUTIONS
10/3/2024 9:54 PM
stabilizing helix - answer✔part of DNA-binding protein that interacts with first helix through
hydrophobic interactions
zinc finger (structure of DNA-Binding Proteins) - answer✔eukaryotic regulatory protein
structure that binds a zinc ion
leucine zipper - answer✔-contains regularly spaced leucine residues
-function is to hold two recognition helices together in correct orientation
possible outcomes of DNA binding - answer✔1. binding protein may catalyze a specific reaction
on the DNA molecule (ex. transcription by RNA polymerase)
2. binding event can block transcription (negative regulation) if protein binds DOWNSTREAM
3. binding event can activate transcription (positive regulation) if protein binds UPSTREAM
negative control - answer✔-regulatory mechanism that stops transcription
-repressor is INHIBITORY (preventing mRNA synthesis)
repression (negative control) - answer✔-preventing the synthesis of an enzyme in response to
sufficient amounts of a product
-has specific effect
-widespread as control for aa and nucleotide precursors
-usually, final product of a biosynthetic pathway represses enzymes
-usually affects biosynthetic/anabolic enzymes
induction (negative control) - answer✔-production of an enzyme in response to presence of a
substrate
-usually affects catabolic enzymes
-ensures enzymes are synthesized only when needed
-turning on an operon that is typically repressed (ex. lac operon)
inducer (negative control) - answer✔-substance that induces enzyme synthesis
-when added, inactivates repressor, so transcription can proceed
corepressor (negative control) - answer✔-substance that represses enzyme synthesis
-bind to an allosteric repressor protein
10/3/2024 9:54 PM
Brock Biology of Microorganisms - Chapter
6 Exam Questions With Correct Answers
Protein-nucleic acid interactions - answer✔these can be site-specific or nonspecific
DNA-binding proteins - answer✔-small molecules that influence that binding of regulatory
proteins to DNA
-most interact with DNA in sequence-specific manner
-specificity provided by interactions between aa side chains and chemical groups on bases and
sugar-phosphate backbone of DNA
-main site for binding is MAJOR GROOVE
inverted repeats - answer✔-useful sequence type
-frequent binding sites for regulatory proteins
-make it easy for protein dimers to form, which can have various uses
domain - answer✔-region of polypeptide with specific structure and function
-in DNA binding, one of these binds to one inverted repeat
-fits in major groove and along backbone
"helix-turn-helix" (structure of DNA-Binding Proteins) - answer✔-(two a-helices connected by a
short 'turn' sequence)
-first helix is recognition helix
-second helix is stabilizing helix
-common in Bacteria (ex. lac and trp repressors in E.coli)
recognition helix - answer✔part of DNA-binding protein that interacts specifically with DNA
, ©SIRJOEL EXAM SOLUTIONS
10/3/2024 9:54 PM
stabilizing helix - answer✔part of DNA-binding protein that interacts with first helix through
hydrophobic interactions
zinc finger (structure of DNA-Binding Proteins) - answer✔eukaryotic regulatory protein
structure that binds a zinc ion
leucine zipper - answer✔-contains regularly spaced leucine residues
-function is to hold two recognition helices together in correct orientation
possible outcomes of DNA binding - answer✔1. binding protein may catalyze a specific reaction
on the DNA molecule (ex. transcription by RNA polymerase)
2. binding event can block transcription (negative regulation) if protein binds DOWNSTREAM
3. binding event can activate transcription (positive regulation) if protein binds UPSTREAM
negative control - answer✔-regulatory mechanism that stops transcription
-repressor is INHIBITORY (preventing mRNA synthesis)
repression (negative control) - answer✔-preventing the synthesis of an enzyme in response to
sufficient amounts of a product
-has specific effect
-widespread as control for aa and nucleotide precursors
-usually, final product of a biosynthetic pathway represses enzymes
-usually affects biosynthetic/anabolic enzymes
induction (negative control) - answer✔-production of an enzyme in response to presence of a
substrate
-usually affects catabolic enzymes
-ensures enzymes are synthesized only when needed
-turning on an operon that is typically repressed (ex. lac operon)
inducer (negative control) - answer✔-substance that induces enzyme synthesis
-when added, inactivates repressor, so transcription can proceed
corepressor (negative control) - answer✔-substance that represses enzyme synthesis
-bind to an allosteric repressor protein
