Q.91 The TATA box is found in the vicinity of the transcription start site. The role of this box is to
(A) serve as a ribosome recruitment site
(B) serve as RNA polymerase binding site
(C) provide 3-D structural integrity to a DNA molecule
(D) act as a terminator sequence
The TATA box serves as a critical promoter element in eukaryotic transcription, positioned about 25-35 base pairs upstream of the transcription start site. This MCQ tests core molecular biology knowledge relevant to genetics and biotechnology students. Here’s the correct answer with breakdowns for exam success.
Correct Answer: None directly match precisely, but closest contextually aligns with recruitment for RNA polymerase positioning (often tested as B in simplified MCQs). Standard role: Binding site for TBP to assemble initiation complex.
TATA Box Core Function
The TATA box (consensus sequence TATAAA) binds TATA-binding protein (TBP), a subunit of TFIID. This recruits other transcription factors and RNA polymerase II to form the pre-initiation complex, precisely positioning transcription at the start site. It defines transcription direction and ensures accurate initiation, not direct polymerase binding.
Why Options Fail or Partially Fit
Options mix promoter roles with unrelated processes:
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(A) Ribosome recruitment site: Incorrect. Ribosomes bind mRNA Shine-Dalgarno/5′ cap sequences post-transcription for translation, not DNA promoters like TATA.
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(B) RNA polymerase binding site: Partially accurate in broad terms but imprecise. TBP binds TATA, then recruits Pol II indirectly; TATA itself isn’t the direct Pol II site.
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(C) 3-D structural integrity to DNA: Wrong. TATA aids unwinding for open complex but doesn’t maintain DNA structure; histones/chromatin handle that.
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(D) Terminator sequence: False. Terminators (e.g., poly-A signals) end transcription downstream; TATA is upstream promoter.
| Option | Matches TATA Role? | Key Reason |
|---|---|---|
| (A) Ribosome site | No | Translation, not transcription |
| (B) Pol binding | Closest indirect | Recruits via TBP |
| (C) DNA integrity | No | Structural role elsewhere |
| (D) Terminator | No | Ends, not starts transcription |
Exam Relevance
For molecular biology or bioinformatics exams, note TATA’s role in gene regulation—mutations alter expression. Visualize in tools like UCSC Genome Browser for promoter alignments. Pairs with glycolysis topics from prior queries for respiration-transcription links.
