RNA: extended from 5' to 3'; single-stranded;
Transcription initiates at promoters: binding of RNA polymerase, accessory proteins
The process of transcription consists of initiation, elongation, and termination
Transcription is the synthesis of RNA from a DNA template
DNA need to be unwrapped from histone core for transcription to proceed
Central dogma of molecular biology: information flows from gene to protein.
RNA polymerase adds ribonucleotides to 3'-OH end, following Watson-Crick base pairing
The RNA strand is complementary and antiparallel to the DNA template.
U instead of T is used.
RNA polymerases: enzymes that catalyze the synthesis of RNA
Accessory proteins: e.g. sigma factor, general transcription factors
Functions of RNAs
All RNA come from transcription.
Only mRNA produce protein.
Nucleus and cytoplasm
Carries genetic code for proteins
Helps incorporate amino acids into polypeptide chain
Structural and functional components of the ribosome
1. RNA polymerase binds to promoter DNA sequences
2. RNA polymerase separates the DNA strand to create a transcription bubble (promoter opening)
3. Ribonucleoside triphosphate are added
4. Polymerase moves past the promoter and becomes stably bound to DNA (promoter clearance)
1. RNA polymerase moves along template strand and elongate the RNA transcript
2. RNA polymerase unwinds duplex ahead of it to expose single strand template. DNA strands behind RNA polymerase pairs again to reform DNA duplex.
3. The growing RNA transcript is extruded through the RNA polymerase
RNA polymerase dissociates from DNA template when it encounters a terminator sequence.
Longer than mRNA
1. Addition of 5' cap
2. Addition of poly(A) tail
introns removed, exons spliced together