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BCH 100 Final questions with correct answers
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BCH 100 Final questions with correct answers
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BCH 100 FinalWhich subunit of the bacterial RNA polymerase holoenzyme binds the -10 and -35 promoter sequences?
- correct answer ✔✔The sigma subunit
What is the general name of enzymes separating DNA strands? - correct answer ✔✔RNA polymerase
Which end of transcribed RNAs has a triphosphate? - correct answer ✔✔The 5' end
Which way is RNA synthesized? - correct answer ✔✔5' to 3' direction
How many strands are there in the transcription bubble? - correct answer ✔✔3
-Nascent RNA strand
-DNA template strand
-DNA coding strand
Is the RNA/DNA hybrid helix right or left-handed? A or B form? - correct answer ✔✔Right-handed
A form
Rho Protein - correct answer ✔✔An ATP-dependent helicase that binds the nascent RNA strand and pulls
it away from RNA polymerase and the DNA template
tRNAs and rRNAs - correct answer ✔✔-Non-coding
-Heavily modified
-Used in protein translation but not translated to proteins
What does S measure? - correct answer ✔✔Svedberg unit
Measures how fast a particle of a given size and shape 'settles', or sediments to the bottom of a test tube
usually under centrifugation
, What does an operon consist of? - correct answer ✔✔-a regulator gene
-an operator
-a promoter
-structural genes
Regulator gene - correct answer ✔✔Encodes a protein
Operator - correct answer ✔✔A cis DNA sequence which is bound with the regulator protein
Promoter - correct answer ✔✔Required for the expression of the structural genes and is under the
control of the operator
Structural genes - correct answer ✔✔Effectors fulfilling the function of the operon
Lac operon - correct answer ✔✔-E. coli uses this operon to adapt to the sugar source change from
glucose to lactose
The regulatory gene encodes a protein called the lac repressor that binds to the operator site in the
absence of lactose and prevents transcription of the structural genes
-Can be stimulated by proteins such as the catabolite activator protein (CAP)
What does B-galactosidase generate? - correct answer ✔✔Galactose and glucose from lactose in a major
reaction
Allolactose in a side reaction
Allolactose - correct answer ✔✔The inducer of the lac operon
What happens when glucose is/isn't present in E. coli? - correct answer ✔✔When glucose is present, the
genes for B-galactosidase, permease, and thiogalactoside transacetylase are expressed at a very low
level
When glucose is not present but lactose is, these enzymes are expressed at a high level
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