RNA synthesis and processing

process of synthesizing RNA from DNA

the initiation of transcription is directed by DNA sequences called promoters which tell the RNA polymerase where to begin

the short stretch of DNA that tells the RNA polymerase where to begin transcription

the template (non-coding) strand of DNA is used as a template by RNA polymerase to add nucleotides in a 5' to 3' direction

certain DNA sequences function as signals to tell the RNA polymerase to terminate transcription

mRNA are capped at their 5' ends with 7-methylguanylate by guanylyl transferase. The capping protects it from exonuclease activity

• Addition of adenylate residues to the 3' terminus of mRNA is cataylzed by poly A polymerase.
• The poly A tail slows the exonucleolytic degradation of mRNA

removal of introns (non coding sequences) while leaving exons (coding seuqences)

Both prokaryotes and eukaryotes are synthesized as large precursors. the precursor rRNA are processed into their mature form by nucleases and methylases

prokaryotes and eukaryotes are also transcribed as precursors which are cleaved and extensively modified

rifampicin

rRNA

mRNA

tRNA