Midterm 2.4.1 Flashcards
(27 cards)
is DNA inert?
yes. it must be converted to RNA via transcription to carry out functions (encode genes)
3 phases of transcription
initiation, transcription/elongation, termination
what is the name of the DNA sequence that guides transcriptional initiation?
promotors
where do promotors reside?
upstream of (before) genes (left)
what determines whether or not a sequence acts as a promotor & if the promoter is active?
binding of sigma factors and regulatory factors
what enzyme is involved in transcription? what is on it that is essential in initiating transcription?
RNA polymerase. a special subunit on RNA polymerase is the sigma factor which binds to DNA
what is sigma factor recognized as? how many sequences does it recognize?
σ70 or RpoD
sequences are ___
degenerate (don’t usually match exactly)
what is special about RpoD and RpoS?
they are sigma factors that are general, and affect many genes. the other sigma factors are specialized
how many bp’s uptream of the transcriptional start site (+1) does RpoD recognize a sequence? (2)
~35 and ~10 (Pribnow box, TATAAT), upstream from the mRNA start site
going upstream goes to which end of the DNA?
5’
what direction would gene x go?
5’ to 3’
what does RNA polymerase do?
it binds to DNA template and makes an RNA copy of one of two strands
it binds to the promoter, signaling the start of a gene
it builds RNA 5’ to 3’ because transcription only goes in one direction
what is RNA polymerase core enzyme made of? (5 subunits)
2 copies of ⍺
β
β’
ω
what does holoenzyme have?
sigma subunit
what does RNA polymerase core enzyme and sigma factor make?
a functional enzyme, holoenzyme
what does core enzyme do>
unwinds DNA to expose template, forms the transcription bubble
what does the RNA chain use as a substrate and guide to build one nucleotide at a time?
NTPs (ATP, CTP, GTP, UTP) as substrates
template strand as a guide
what happens when RNA polymerase encounters a transcriptional terminator?
RNA polymerase will dissociate from the template and release the RNA
when does transcription stop?
when RNAP encounters a transcriptional terminator
RNAP dissociates from DNA stops making RNA and releases transcript
what forms when RNA hairpin structures form, followed by a string of U residues? what do U residues act as? what does the formation of the hairpin do?
intrinsic (rho-independent) terminators
U residues act as a pause signal for RNAP
the formation of the hairpin forces RNAP off the template
central dogma:
DNA is replicated
DNA is transcribed to RNA
RNA is translated to protein
what are rho dependent terminators
protein called Rho binds RNA as it is being transcribed and causes RNA polymerase to dissociate after it encounters certain sequences
3 majors classes of RNA
mRNA - converted to protein via translation
tRNA - functional RNA, used in translation process
rRNA - functional RNAs, used in translation process
