BIOL 473 Exam 1 UPDATED ACTUAL
Exam Questions and CORRECT Answers
trp attenuation high trp - CORRECT ANSWER - -ribosome translates unhindered
-ribosome blocks RNA polymerase from transcribing sequence 2
-3 and 4 form the attenuator structure, stopping the ribosome from translating and kicks the RNA
polymerase off (stops transcription)
-terminator structure is more stable due to more H bonds
trp attenuation low trp - CORRECT ANSWER - -ribosome stalls at the trp codons in the
leader sequence and produces an incomplete leader sequence, allowing the polymerase to bind
-2 and 3 form a secondary structure, which prevents attenuation
-RNA polymerase continues transcription
trp leader sequence - CORRECT ANSWER - contains 2 trp residues and determines which
sequences are paired, has a regulatory role
trp operator - CORRECT ANSWER - nearly palindromic, in the promoter, where the
repressor binds
trp repressor - CORRECT ANSWER - -dimeric (binding site is palindromic), binds to the
operator DNA in the presence of trp to lower it's translation
-helix-turn-helix motif
-it's mRNA codes for a monomer, which dimerizes and trp (co-repressor) binds to it, complex
binds to operator
splicing - CORRECT ANSWER - nuclease cleaves leader from tRNA and removes introns
inosine - CORRECT ANSWER - -nucleotide formed by deamination of adenosine and can
replace A, U, C
, -found in the wobble position in tRNA anticodons
-weaker base pairing interactions
wobble position - CORRECT ANSWER - -position 3 (5' end of tRNA anticodon, 3' end of
mRNA codon), where specific base pairing is less critical to determining the correct amino acid
-means fewer tRNAs are needed to translate mRNA
aminoacylation of tRNAs - CORRECT ANSWER - charging tRNAs with an amino acid
aminoacylation tRNA synthetases - CORRECT ANSWER - -bind specific amino acid to
tRNA through ATP hydrolysis into AMP and pyrophosphate
-contains a synthetic domain and sometimes an editing domain (determines if the amino acid fits)
tRNA specificity - CORRECT ANSWER - -matching amino acids and tRNAs is like a
second genetic code
-distinguishable by the anticodon region, uracil derivatives, post-transcriptional modifications
and other regions (like the G-U region or the D arm)
ribosomal RNAs - CORRECT ANSWER - fold up like a tRNA (not linear), where double
stranded RNAs are more protected
protein translation factors - CORRECT ANSWER - -initiation, elongation, release
-many are GTPases
-vary between prokaryotes and eukaryotes
5 stages to Protein Synthesis - CORRECT ANSWER - -activation of amino acid
(aminoacylation of tRNAs)
-initiation (binding mRNA and fMet to ribosome)
-elongation (binding aminoacylated tRNAs to ribosome, forming peptide bonds)
-termination, ribosome recycling (termination codon in mRNA reaches ribosome)
Exam Questions and CORRECT Answers
trp attenuation high trp - CORRECT ANSWER - -ribosome translates unhindered
-ribosome blocks RNA polymerase from transcribing sequence 2
-3 and 4 form the attenuator structure, stopping the ribosome from translating and kicks the RNA
polymerase off (stops transcription)
-terminator structure is more stable due to more H bonds
trp attenuation low trp - CORRECT ANSWER - -ribosome stalls at the trp codons in the
leader sequence and produces an incomplete leader sequence, allowing the polymerase to bind
-2 and 3 form a secondary structure, which prevents attenuation
-RNA polymerase continues transcription
trp leader sequence - CORRECT ANSWER - contains 2 trp residues and determines which
sequences are paired, has a regulatory role
trp operator - CORRECT ANSWER - nearly palindromic, in the promoter, where the
repressor binds
trp repressor - CORRECT ANSWER - -dimeric (binding site is palindromic), binds to the
operator DNA in the presence of trp to lower it's translation
-helix-turn-helix motif
-it's mRNA codes for a monomer, which dimerizes and trp (co-repressor) binds to it, complex
binds to operator
splicing - CORRECT ANSWER - nuclease cleaves leader from tRNA and removes introns
inosine - CORRECT ANSWER - -nucleotide formed by deamination of adenosine and can
replace A, U, C
, -found in the wobble position in tRNA anticodons
-weaker base pairing interactions
wobble position - CORRECT ANSWER - -position 3 (5' end of tRNA anticodon, 3' end of
mRNA codon), where specific base pairing is less critical to determining the correct amino acid
-means fewer tRNAs are needed to translate mRNA
aminoacylation of tRNAs - CORRECT ANSWER - charging tRNAs with an amino acid
aminoacylation tRNA synthetases - CORRECT ANSWER - -bind specific amino acid to
tRNA through ATP hydrolysis into AMP and pyrophosphate
-contains a synthetic domain and sometimes an editing domain (determines if the amino acid fits)
tRNA specificity - CORRECT ANSWER - -matching amino acids and tRNAs is like a
second genetic code
-distinguishable by the anticodon region, uracil derivatives, post-transcriptional modifications
and other regions (like the G-U region or the D arm)
ribosomal RNAs - CORRECT ANSWER - fold up like a tRNA (not linear), where double
stranded RNAs are more protected
protein translation factors - CORRECT ANSWER - -initiation, elongation, release
-many are GTPases
-vary between prokaryotes and eukaryotes
5 stages to Protein Synthesis - CORRECT ANSWER - -activation of amino acid
(aminoacylation of tRNAs)
-initiation (binding mRNA and fMet to ribosome)
-elongation (binding aminoacylated tRNAs to ribosome, forming peptide bonds)
-termination, ribosome recycling (termination codon in mRNA reaches ribosome)
