Proteinbiosynthesis Transcription Flashcards
1
Q
What are the three phases of transcription?
A
Initiation, elongation, termination
2
Q
What happens during initiation of transcription?
A
- formation of transcription complex at the promoter sequence, including TATA box and transcription factors
- allows RNA polymerase II to bind to the promoter sequence
- unwinds DNA
- separates it into complementary single strands
3
Q
What happens during elongation of transcription?
A
- RNA polymerase II synthesizes pre-mRNA in the 5‘ to 3‘ direction by adding complementary nucleotides
- 5‘ cap (modified guanine) added
- poly(A)-tail to the pre-mRNA added
- splicing occurs to remove introns and join exons
4
Q
How does transcription terminate?
A
RNA polymerase II disassociates form the DNA at the terminator sequence, releases mRNA
5
Q
What is the function of the 5‘ cap?
A
Protect pre-mRNA from degradation
6
Q
What is the function of a poly(A)-tail?
A
Help with initiating translation
7
Q
How are introns cut out by the pre-mRNA?
A
Spliceosomes
8
Q
What is a spliceosome?
A
Complex consisting of proteins and snRNAs
