TRANSCRIPTION Flashcards
the process by which a complementary RNA molecule is synthesized from a DNA template strand
DNA Transcription
First step in gene expression
Transcription
carries the genetic information from the DNA to the ribosomes, where it is used to guide the synthesis of proteins
mRNA
signals the start of a gene and determines the direction of transcription
PROMOTER SEQUENCE
Only one of the two DNA strands serves as the template for transcription, called
ANTISENSE STRAND OR NON-CODING STRAND
UNTRANSCRIBED STRAND IN TRANSCRIPTION
SENSE STRAND OR CODING STRAND
TERMINATION
contain a specific sequence that forms a stable hairpin structure in the RNA transcript, followed by a string of uracil (U) residues. This structure causes the RNA polymerase to dissociate from the DNA template.
INTRINSIC TERMINATORS
INTRINSIC TERMINATION
TERMINATION
binds to the growing RNA chain and helps to release RNA polymerase from the DNA.
RHO
RHO-DEPENDENT TERMINATION
The pre-mRNA is capped at the 5’ end with a ———————, which protects the mRNA and helps with ribosome binding.
7-methylguanosine cap
Introns, non-coding regions within the pre-mRNA, are removed through a process called —————-, leaving only the exons, which contain protein-coding information.
SPLICING
A —————————– tail is added to the 3’ end of the mRNA, which aids in mRNA stability and translation.
POLYADENINE (POLY-A)
TRUE OR FALSE
Transcription process includes initiation, elongation, and termination, and in eukaryotes, it is followed by post-transcriptional modifications to produce mature mRNA
TRUE
TRUE OR FALSE
Transcription is DNA-independent
FALSE, it is DNA-dependent RNA synthesis
it uses the anti-sense strand, which complements the RNA molecule
TRUE OR FALSE
THE RNA POLYMERASE IN TRANSCRIPTION HAS NO PROOFREADING ABILITY
TRUE
RNA Polymerase: 6 sites of activity
DNA coding strand
DNA template strand
RNA binding
RNA-DNA hybrid
Unwinding point
Rewinding point
Requirements for Transcription
- Specific Sequences
- Promoters
- Interaction of RNA polymerase with several proteins (TF)
- Sequence that “promote” gene expression
- Binding site of RNA polymerase
PROMOTER
PROKARYOTIC PROMOTERS
10 BASES BEFORE STARTPOINT; CONSENSUS SEQUENCE - TATAAT
Pribnow Box
PROKARYOTIC PROMOTERS
upstream from the Pribnow box; Consensus sequence - TTGACA
35 SEQUENCE
EUKARYOTIC PROMOTERS
- TATAWAW;
- 19-27 bases before startpoint;
- Binding site of TFIID;
- Aids Binding of RNA polymerase
TATAbox or Goldberg or Hogness Box
EUKARYOTIC PROMOTERS
- ~ 70 BASES BEFORE STARTPOINT
CCAAT box
EUKARYOTIC PROMOTERS
~40 base before startpoint
GC Box
- position RNA polymerase at the promoter and send it on its way
- sufficient to direct basal level of transcription from many core promoters
- essential for transcription initiation for any eukaryotic gene
- protein factors
TRANSCRIPTION FACTORS
Bind promoters; Melts DNA; Remains stationary until phosphorylated; incorporates the first ribonucleotide; three phosphate groups retained
RNA polymerase activity during initiation
TRANSCRIPTION
The DNA strand known as the ————– strand is used to make a complementary copy of RNA, resulting in an RNA-DNA hybrid
template
TRANSCRIPTION
RNA polymerase moves along the template strand in a 3’ to 5’ direction, and the RNA is synthesized in a ——————-using nucleoside triphosphates as precursors.
5’ to 3’ direction
TRANSCRIPTION TERMINATION
Simple termination; DNA template ends in AAAAA; palindrome rich in GC; mRNA forms a hairpin
RHO-INDEPENDENT TERMINATION
TRANSCRIPTION TERMINATION
Requires rho factor; binds to the rut site; palindrome: less in GC-rich; no UUUUU at the end of RNA; USES RHO-HELICASE TO RELEASE RNA FROM THE TRANSCRIPTION BUBBLE
Rho-dependent termination
protein-coding sequences
exons
non-coding protein
introns
BACTERIA: -35 AND -10 SEQUENCES: EUKARYOTES: ________________
PROMOTER
TATA box
bacteria: 1 RNA polymerase: eukaryotes: ———–
3 types of RNA polymerases; RNA pol II transcribes protein-encoding genes
site of transcription in Eukaryotes
NUCLEUS
Site of transcription in Prokaryotes
CYTOPLASM
