Handout Notes from Mak:
Hopefully these notes will aid you in understanding some of the ideas in
transcription and translation.
From Gene to Protein:
Most of the organisms (including eukaryotic and prokaryotic cells) use DNA as the genetic
materials. In order to turn this genetic information into a functional protein, all cells carry out
transcription and translation: Transcription: DNA
mRNA; Translation: mRNA
Taken together, they make the central dogma of Biology: DNA
Here is an overview.
DNA serves as the template for the synthesis of RNA
, binds to the promoter of gene (with core elements like -10
TATA box and -35 element).
In prokaryotes, factor sigma which recognized the core elements comes in (In eukaryotes,
a lot of different factors are required) ; working together, they generate the open structure
of the transcription initiation complex and with the helicase activity, open the DNA
double helix (formation of transcription bubble).
RNA polymerase proceeds down one template DNA strand moving in the 3' -> 5'
as it does so, it assembles
nucleotides (supplied as triphosphates, e.g., ATP, UTP,
CTP, GTP) into a strand of RNA in 5’ to 3’ direction.
each ribonucleotide is inserted into the growing RNA strand following the rules of base
pairing. Thus for each C encountered on the DNA strand, a G is inserted in the RNA; for
each G, a C; and for each T, an A. However, each A on the DNA guides the insertion of
the pyrimidine uracil (
, from uridine triphosphate, UTP). There is no T in RNA.
synthesis of the RNA proceeds in the 5' -> 3' direction.
The elongation complex is stabilize by accessory factors like NusA and the formation of
RNA/DNA hybrid in complex.
Until the RNA polymerase reads a Termination Signal (Rho-independent termination
signal with stem loop structure + a stretch of U residues in RNA; Rho-dependent
termination signal (with stem loop structure + Rho protein), it will then starts to
dissociated from the DNA template and the so form mRNA release. In prokaryotics,
because there is no compartmentization in the cell, transcription is coupled with