RNA synthesis or transciption Flashcards
monomers
are NMP (AMP,GMP,TMP,CMP)
secondary structure
DNA contains an inverted repeat, RNA transcription forms a stem loop
types of RNA
mRNA encodes the primary structure of a polypeptide as codons
tRNA all have the same secondary and tertiary structure
rRNA 50S and 30S ribosomal subunit
RNA polymerase strucutre
core enzyme is composed of 5 polypeptides, 2a, b,b1, gamma. has polymerase activity. holoenzyme = core enzyme + sigma factor
what is the sigma factor
required for RNA polymerase to recognize the correct region, called promotor on the DNA to bind and begin synthesis
RNA polymerase fn
like DNA pol, uses DNA as template. unlike DNA pol, RNA pol can recognizes were to start synthesis. does not need other enzymes to break H2 bonds of dsDNA. does not need a primer. substrates are NTPs, like DNA
what is a gene
region of DNA that encodes for one piece of RNA (rRNA econdes proteins, tRNA and mRNA do not encode proteins)
transcription initiation
the sigma factor of the RNA pol holoenzyme recognises and binds to promoter. enzume unwinds and separates dsDNA. the first NTP porvides free 3’ OH used for elongation
where does RNA transcription start
+1 site, RNA synthesis proceeds in 5’—>3’ direction
elongation of transciption
after 12 nucleotides have been synthesized, the sigma factor dissociates and core enzyme synthesizes RNA that is complementary and anti parallel to template strand. DNA strands reform H bonds displacing the strand of newly synthesized RNA
factor independent termination
the terminator sequence of the gene includes an inverted repeat followed by 6 A=T base pairs. terminator region is transcribed and form a stem loop that cause RNA pol to pause. after stem loop are 6 U. The A=U base pairs are weak and RNA pol falls off
promoter structure and fn
2 conserved sequences at -35 and -10 (6 nucleotides long) TTGACA and TATAAT. most common bases are called consensus sequences, recognized by main sigma factor in E. coli sigma70
