Question

When considering the initiation of transcription, one often finds consensus sequences located in the region of the DNA where RNA polymerase(s) bind. Which are common consensus sequences?

1) GGTTC, TTAT
2) TTTTAAAA, GGGGCCCC
3) trinucleotide repeat
4) CAAT, TATA
5) satellite DNAs

Answer 1

Common consensus sequences for the initiation of transcription include the TATA box (TATAAT) found in the core promoter region, and in eukaryotes, the CAAT box and GC-rich or octamer boxes, which bind transcription factors to regulate gene expression.

Step-by-step explanation:

When initiating transcription, the RNA polymerase binds to specific DNA sequences known as promoter regions. These regions contain consensus sequences, which are DNA motifs recognized by various transcription factors. For prokaryotic promoters, the conserved consensus sequences at the -10 and -35 regions upstream of the initiation site are TATAAT (known as the TATA box) and TTGACA, respectively. In terms of the common consensus sequences listed in the question, option 4 (CAAT, TATA) includes the TATA box which is part of the core promoter region and critical for the binding of the transcription machinery.

In eukaryotic promoters, apart from the TATA box, other important elements include the CAAT box (GGCCAATCT) and GC-rich boxes or octamer boxes that enhance the efficiency of transcription initiation. These sequences are essential for binding various transcription factors that regulate the transcription process.