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Transcription in Eukaryotes
33 cards·by davisn3
How many types of RNA polymerase do Prokaryotes have?
One
What do RNA polymerase transcribe?
mRNAs, tRNAs, and rRNAs
How many types of RNA polymerase do Eukaryotes have?
Three
what does RNA polymerase I do?
transcribes three major rRNAs 28S, 18S, 5.8S
What does RNA polymerase II do?
transcribes mRNAs and some snRNAs
What does RNA polymerase III do?
transcribes tRNAs, 5S rRNA, and snRNAs
What does S values of rRNAs refer to?
molecular size, as determined in a sucrose gradient
What are the Two general regions of the promoter?
Core promoter and Promoter proximal elements
Facts about Core promoter:
near the transcription start, -30 bp, Short sequence Inr (initiator) (defined as +1), “TATA
Box” = TATAAAA
Which is easier to denature AT-rich DNA or GC-rich DNA?
AT-rich DNA
Facts about Promoter proximal elements:
located upstream from the TATA box, ~-50 to -200 bp, “Cat Box” = CAAT and “GC Box” GGGCGG.
Where is Promoter proximal elements important in?
Important in determining how and when a gene is expressed
What is required by RNA polymerases?
Transcription factors (TFs)
What are TFs?
proteins that bind to basal promoter elements
What occurs in a set order in protein coding genes?
Binding of TFs and RNA polymerase
what is a pre-initiation complex (PIC)?
Complete complex (RNA polymerase + TFs)
what are Activators?
transcription regulatory protein which determine the efficiency of transcription
initiation
What are Enhancers?
short sequence elements that are usually found upstream from the transcription initiation
site
What are Enhancers required for?
the maximal transcription of a gene.
How is High-level transcription induced?
by binding of activator factors to DNA sequences
What are the Three main parts of the mRNA Molecule?
5ʼ untranslated region leader sequence, Coding sequence, specifies amino acids to be
translated, 3ʼ untranslated region trailer sequence
What happens After 20-30 nucleotides have been synthesized and results in what?
the 5ʼ-end of the mRNA is capped 5ʼ to 5ʼ with a guanine nucleotide and Results in the addition of
two methyl (CH3) groups.
What is the 5' cap essential for?
for the ribosome to bind to the 5ʼ end of the mRNA
What does the Poly (A) tail do?
Stabilizes the mRNA, and plays an important role in transcription termination and export of
mRNA from the nucleus to the cytoplasm
What is Poly (A) tail?
50-250 adenine nucleotides are added to 3ʼ end of mRNA.
What are introns?
non-coding DNA sequences between exons in a gene.
What are exons?
expressed DNA sequences in a gene, code for amino acids
Is mRNA transcript mature in Prokaryotes or Eukaryotes?
Prokaryotes
Transcription and translation are not coupled in which? ( Prok.or Euk.)
Eukaryotes
What does it mean that Eukaryote mRNAs are monocistronic?
its a type of messenger RNA that can encode only one polypeptide per RNA molecule
What does it mean that Prokaryote mRNAs are polycistronic?
they contain amino acid coding information for more than one polypeptide separately within
the same RNA molecule
Type I Rho- independent (ρ-independent)
Intrinsic- inverse repeat forms a hairpin loop and is believed to physically destabilize the
DNA-RNA hybrid.
Type II Rho- dependent (ρ-dependent)
Involves ρ factor proteins, believed to break the hydrogen bonds between the template DNA and
RNA.