Transcription and mRNA Processing Flashcards
What is the role of RNA polymerase?
Catalyze RNA synthesis; pries DNA strands apart and joins together RNA nucleotides
What is a promoter?
Area where factors bind to DNA
What is the upstream sequence?
Anything before the start codon
What is the terminator?
Area after the stop codon telling RNA polymerase to stop coding
What is the transcription termination site?
Area where the RNA polymerase releases from the strand
What is the transcription initiation site?
Area where the RNA polymerase starts coding
What are the stages of transcription?
- Initiation- start of transcription
- Elongation- growth or elongation (actual synthesis)
- Termination- ending transcription
Does initiation require ATP?
YES
Does the initiation process have 3’ to 5’ exonuclease activities?
NO
Where does transcription being in eukaryotic promoters?
TATA Box
What is the name of the complete complex one the transcription factors bind to the DNA?
Transcription initiation complex
What direction does elongation take place?
5’ to 3’
Does transcription need a primer to help process occur?
NO
What type of cell has pre-mRNA?
Eukaryotes
How does RNA polymerase know when to release from DNA strand?
The transcription will force the RNA to change shape and stop the process
What is the polyadenylation signal sequence?
AAUAAA sequence after the stop codon that makes the RNA stop and release from DNA strand in eukaryotes
Why does a eukaryotic cell add a 5’ cap and 3’ Poly-A tail?
Mediate mRNA to reach the cytoplasm
What is the reason for the caps at the ends of pre-mRNA?
- Facilitate mRNA export to cytoplasm
- Protect mRNA from hydrolytic enzymes
- Helps ribosomes attach to 5’ end
What is found in the 5’ cap?
Modified guanine nucleotide with 3 phosphates
The polyadenylation signal tells the RNA to make what?
3’ Poly-A (adenine) tail
What will the caps do to the pre-mRNA?
Bond together and form a closed-loop structure for protection, transport, and ribosome binding
What is RNA splicing?
Removal of intron sequences which leave exons only
Are exons or introns expressed?
Exons are expressed
Introns are indentified by consensus sequences: _ _ at the start and _ _ at the other end.
GT
AG
What is the spliceosome?
Area that identifies the beginning and end of transcription
What is the job the small RNA in the splicosome?
Removal of introns
What is the role of ribozymes?
Catalytic RNA molecules that function as enzymes
How do ribozymes act as a catalyst? (3)
- Can form 3D structures- complementary base pairing
- Some bases in RNA contain functional groups that may participate in catalysis
- RNA may H-bond with other nucleic acid molecules
Why do we have introns?
Ribozymes and some introns contain sequencing that may regulate gene expression
What is alternative RNA splicing?
Not all exons are expressed, a cell can splice out introns and exons to form different types of proteins
