A. Polyadenylation signals in mammalian cells consist of the hexanucleotide AAUAAA in addition to upstream and downstream (U- or GU-rich) elements
B. Polyadenylation signals in mammalian cells consist of the hexanucleotide GGUAAA in addition to upstream and downstream (U- or GU-rich) elements
C. Poly-A polymerase adds a poly-A tail consisting of about 50 Adenines (A) to the 3' end of the RNA
D. Poly-A polymerase adds a poly-A tail consisting of about 200 Adenines (A) to the 3' end of the RNA
Choose the correct answer from the options given below:
Poly-A Tail Addition Overview
Polyadenylation is a critical post-transcriptional modification where a string of adenine nucleotides, known as a poly-A tail, is added to the 3' end of a messenger RNA (mRNA) precursor molecule (pre-mRNA). This process plays a vital role in mRNA stability, nuclear export, and translation initiation.
Analyzing Polyadenylation Signals
- Statement A: Correct. In mammalian cells, the primary polyadenylation signal is the hexanucleotide sequence $AAUAAA$, or a close variant. This sequence is located upstream of the cleavage site. Additionally, upstream (U-rich) and downstream (GU-rich) elements contribute to the efficiency and specificity of polyadenylation.
- Statement B: Incorrect. The sequence $GGUAAA$ is not the standard or primary polyadenylation signal in mammalian cells. The conserved signal is $AAUAAA$.
Poly-A Tail Length
- Statement D: Correct. Following cleavage, the enzyme Poly-A polymerase (PAP) adds a long chain of adenine nucleotides. This poly-A tail typically consists of approximately 100 to 250 Adenines (A), with around 200 being a common length. This extensive tail enhances mRNA stability and influences its lifespan.
- Statement C: Incorrect. A poly-A tail of only about 50 Adenines is generally considered too short to fulfill the regulatory functions associated with mature eukaryotic mRNA. The functional length is significantly longer.
Conclusion on Correct Statements
Based on the established mechanisms of pre-mRNA processing, statements A and D accurately describe key aspects of poly-A tail addition in mammalian systems.
Similar Questions
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Choose the correct answer from the options given below:
Important Questions from Mixed Topic (CUET PG)
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B. Politics is an autonomous sphere of action and cannot therefore be reduced to morals
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Choose the correct answer from the options given below:Who among the following political thinkers consider the anarchical self help system to be a compelling factor for States to maximise their relative power positions?
