4. Among the following which statement is correct regarding the promoter of the eukaryotic gene?
(1) It is always located upstream of transcription start site
(2) It is located downstream of translation start site
(3) Different promoter elements are recognized by different RNA polymerase
(4) Promoters are recognized due to their different secondary structures

Understanding the Eukaryotic Gene Promoter: Correct Statement Explained

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Discover the correct location and function of eukaryotic gene promoters, their key elements, and why they are essential for transcription initiation. Perfect for CSIR NET Life Science exam preparation.

Correct Answer

(1) It is always located upstream of transcription start site

Detailed Explanation

The promoter of a eukaryotic gene is a specialized DNA region that plays a crucial role in regulating gene expression. Here’s why option (1) is correct:

Promoter Location and Structure

• The promoter region is typically located upstream (towards the 5’ end) of the gene’s transcription start site (TSS). This means it is found before the point where RNA polymerase begins synthesizing RNA.

• The core promoter includes essential elements such as the TATA box, initiator (Inr), and other motifs, usually spanning from about -35 to +35 nucleotides relative to the TSS. The TATA box, for example, is often found 25–30 base pairs upstream of the TSS.

• Proximal and distal promoter elements may be located further upstream and contain regulatory sequences that bind transcription factors to modulate gene expression.

Function of the Promoter

• The promoter serves as the binding site for RNA polymerase and general transcription factors, initiating the assembly of the transcriptional machinery.

• It determines where transcription begins and how efficiently a gene is transcribed.

Why Other Options Are Incorrect

• Option (2): The promoter is not located downstream of the translation start site; it is always upstream of the transcription start site, which itself is upstream of the translation start site.

• Option (3): While different RNA polymerases recognize different promoter sequences, a single promoter is not recognized by multiple polymerases for the same gene in eukaryotes.

• Option (4): Promoters are recognized primarily by their DNA sequence motifs, not by secondary structures.

Summary Table

Conclusion

The eukaryotic gene promoter is always located upstream of the transcription start site, serving as the critical region for the initiation of transcription and regulation of gene expression. Understanding promoter structure and function is foundational for molecular biology and essential for CSIR NET Life Science exam success.