transcription Flashcards
give 3 similarities between DNA replication and transcription
- Both processes use DNA as the template.
- Both synthesis directions are from 5´ to 3´.
- Phosphodiester bonds are formed in both cases
give 5 differences between DNA replication and protein synthesis
- double/single strands
- substrates- dNTP/NTP
- DNA polymerase/RNA polymerase
- product- dsDNA/ssRNA
- thymine/uracil
what are structural genes
DNA regions that can be transcribed into RNA
what is the antisense strand
template strand
what is the sense strand
coding strand i.e. the strand whose base sequence specifies the amino acid sequence of the encoded protein
what is it called when transcription direction on different strands is opposite
asymmetric transcription
what is the function of the α, β, β’, and σ subunits in bacterial RNA polymerase
α- Determine the DNA to be transcribed
β- Catalyze polymerization
β’- Bind & open DNA template
σ- Bind & open DNA template
what does Rifampicin do
therapeutic drug for tuberculosis treatment, can bind specifically to the beta subunit of RNA-pol, and inhibit the RNA synthesis
what does one operon include
several structural genes and upstream regulatory sequences (or regulatory regions)
what is the -35 region of TTGACA sequence
recognition site and the binding site of RNA-pol
what is -10 region of TATAAT (pribnow box)
region at which a stable complex of DNA and RNA-pol is formed
what is the consensus sequence
a sequence of DNA having similar structure and function in different organisms
what do the RNA polymerase holoenzyme and promoter form
closed promoter complex
how does the open promoter complex form
when polymerase unwinds about 17 pairs
what is a holoenzyme
the core enzyme saturated with sigma factor
in bacteria what sequence does the RNA pol recognize and then after slides to
TTGACA region and TATAAT region
what is the first nucleotide on RNA transcript
purine triphosphate
when does the sigma subunit fall of from the RNA pol
once the first 3 prime,5 prime phosphodiester bond is formed
where are the free NTPs added in bacteria
sequentially to the 3 prime -OH of the nascent RNA strand
what forms the transcription bubble in bacteria
RNA-pol, DNA segment (~40nt) and the nascent RNA
what
a) hybridizes with the DNA template
b) extends out the transcription bubble as the synthesis is processing
(in bacteria)
a) 3 prime segment
b) 5 prime segment
what do RNA polymerases I, II and III transcribe respectively
rRNA, mRNA and tRNA genes, respectively
what transcribes other RNAs as well
RNA polymerase III
what are cis and trans regulatory products
- cis-regulatory elements are present on the same molecule of DNA as the gene they regulate (often binding sites for one or more transacting factors)
- trans-regulatory elements can regulate genes distant from the gene from which they were transcribed
what are the cis- acting elements
- Promotor
* Enhancer
what is a region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur
enhancer
enhancers are only in eukaryotes, true or false
false, they are in both eukaryotes and prokaryotes
what are the three cis acting elements that help
polymerase II initiate transcription in eukaryotes
TATA box (determine the starting point of transcription by
facilitating the unwinding of the helix)
CAAT box
GC box
what are the functions of the transacting elements
1) interact with cisacting elements to control transcription initiation
2) facilitate binding to the DNA template
what do most transcription factors do during elongation
Most of the TFs fall off from from the pre-initiation complex
what is the termination sequence in eukaryotes
AATAAA followed by GT repeats
what is the primary transcript also called
heteronuclear RNA
what are the postmodifications that occur on RNA
- Capping at the 5- end
- Tailing at the 3- end
- mRNA splicing
- RNA edition
what is the 5 prime cap
7-methylguanosine cap which is a modified guanine (G)
nucleotide
what enzyme catalyzes the additions of 200 A nucleotides to the 3′ end of the just cleaved pre-mRNA
Poly (A) Polymerase (PAP)
when cleaving, what does the endonuclease-containing protein complex bind to
AAUAAA sequence upstream of the cleavage site and to a GU-rich sequence downstream of the cut site
what does the spliceosome do
spliceosome removes introns from a transcribed pre-mRNA
what is RNA editing
may include the insertion, deletion, and base substitution of nucleotides within the RNA molecule (rare)
what are the four rRNAs in eukaryotes first transcribed as
two long precursor molecules
why are some of the bases of pre-rRNAs methylated
for added stability
all of ribosome’s RNA is structural, true or false
False. Some of a ribosome’s RNA molecules are purely structural, whereas others have catalytic or binding activities
what is the first step in processing tRNA
digestion of the RNA to release individual pre-tRNAs
what are the five steps in converting the pre-tRNA to a mature tRNA
(1) The 5′ end of the pre-tRNA, called the 5′ leader sequence, is cleaved off
(2) The 3′ end of the pre-tRNA is cleaved off
(3) a CCA sequence of nucleotides is added to the 3′end of the pre-tRNA
(4) Multiple nucleotides in the pre-tRNA are chemically
modified, altering their nitrogen bases
(5) introns that have to be spliced out
what are the most common modifications of tRNA nucleotides
conversion of adenine (A) to pseudouridine (ψ), the conversion of adenine to inosine (I), and the conversion of uridine to dihydrouridine (D)
