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During transcription, holoenzyme RNA polymerase binds to a DNA sequence and the DNA assumes a saddle like structure at that point. What is the sequence called -
A
CAAT box
B
GGTT box
C
AAAT box
D
TATA box
Detailed Solution
The promoter is the DNA sequence upstream of a gene to which RNA polymerase binds to start transcription.
It contains a conserved A-T rich sequence called the TATA box (the Pribnow box, TATAAT, in prokaryotes; the Hogness box, TATAAA, in eukaryotes), located about 10 to 25 base pairs upstream of the start site.
The RNA polymerase holoenzyme (with the sigma factor in prokaryotes, or with the TATA binding protein in eukaryotes) binds here, sits on the DNA like a saddle and bends it.
The A-T pairs have only two hydrogen bonds, so the strands open easily at this point and transcription begins.
The CAAT box is another promoter element further upstream, but it is not the site where the DNA takes this saddle shape.
So the sequence is called the TATA box.
It contains a conserved A-T rich sequence called the TATA box (the Pribnow box, TATAAT, in prokaryotes; the Hogness box, TATAAA, in eukaryotes), located about 10 to 25 base pairs upstream of the start site.
The RNA polymerase holoenzyme (with the sigma factor in prokaryotes, or with the TATA binding protein in eukaryotes) binds here, sits on the DNA like a saddle and bends it.
The A-T pairs have only two hydrogen bonds, so the strands open easily at this point and transcription begins.
The CAAT box is another promoter element further upstream, but it is not the site where the DNA takes this saddle shape.
So the sequence is called the TATA box.