Translation and Transcription in Prokaryotes Flashcards
What is Translation ?
Process of synthesis of proteins by encoding information on mRNA .
Subsequent post translational processing of the protein molecule .
What is Transcription ?
The production of messenger RNA by the enzyme RNA polymerase and processing of the resulting mRNA molecule
How does the process of Transcription work ?( Promoter)
Promoter is a DNA sequence in which the transcription binds initiating transcription .
Promoter exist upstream of the gene they regulate.
Specific sequence of a promoter is important it determines whether corresponding gene is transcribed all time .
What happens during the initiation process?(Transcription)
At -10 and -35 region, -10 region being TATAAT -35 sequence ,TTGACA being recognised /bound to 6 factor .
Once the interaction is made the subunit of the core enzymes bind to the site , A- T rich - 10 region facilitates unwinding of the DNA template , with several phosphodi ester bonds being made
Transcription initiation phase ends with the production of abortive transcripts ,with 10 nucleotides made and released .
What is the process of elongation ?(Transcription)
It begins with 6 subunits from polymerase .The dissociation of 6 allows the core RNA polymerase , enzyme to proceed along the DNA template synthesising in 5- 3 direction of rate of 40 nucleotides per second
DNA continually unwound ahead of core enzyme and rewound behind it
Base pairing between DNA and RNA isn’t stable enough to maintain stability the mRNA synthesis components , RNA polymerase acts as a stable link between DNA template .Ensuring there is no disruptive
Once the gene is transcribed ,the prokaryotic polymerase needs to be instructed to dissociate from DNA template/Newly made mRNA .
How does the process of Termination work ? RHO dependent (Transcription)
There are two types of termination signals
Rho-dependent termination is controlled by the rho protein, which tracks along behind the polymerase on the growing mRNA chain. Near the end of the gene, the polymerase encounters a run of G nucleotides on the DNA template and it stalls.
As a result, the rho protein collides with the polymerase. The interaction with rho releases the mRNA from the transcription bubble.
How does the process of Termination work ? RHO independent (Transcription)
Rho-independent termination is controlled by specific sequences in the DNA template strand. As the polymerase nears the end of the gene being transcribed, it encounters a region rich in C–G nucleotides.
The mRNA folds back on itself, and the complementary C–G nucleotides bind together. The result is a stable hairpin that causes the polymerase to stall as soon as it begins to transcribe a region rich in A–T nucleotides.
The complementary U–A region of the mRNA transcript forms only a weak interaction with the template DNA. This, coupled with the stalled polymerase, induces enough instability for the core enzyme to break away and liberate the new mRNA transcript.
