Question

A key modification in the 3′ end of eukaryotic mRNA is the addition of 50 to 250 adenine nucleotides at the 3′ end, forming a poly(A) tail. Which of the following statements is not a salient feature of this polyadenylation reaction?

a) Enhances stability of mRNA
b) Facilitates export of mRNA to the cytoplasm
c) Signals termination of transcription
d) Aids in splicing of introns
e) Participates in the initiation of translation

Answer 1

The polyadenylation reaction, which adds a poly(A) tail to eukaryotic mRNA, indeed enhances mRNA stability, facilitates its export, aids in splicing, and assists in translation initiation, but it does not signal the termination of transcription.

Step-by-step explanation:

The statement that is not a salient feature of the polyadenylation reaction in eukaryotic mRNA is (c) Signals termination of transcription. Polyadenylation, which involves the addition of a poly(A) tail to the 3' end of pre-mRNA, serves several functions:

• (a) Enhances stability of mRNA
• (b) Facilitates export of mRNA to the cytoplasm
• (d) Aids in splicing of introns
• (e) Participates in the initiation of translation

However, the poly(A) tail does not signal the termination of transcription; instead, transcription is usually terminated after a series of specific sequences downstream of the coding sequence. The poly(A) tail is added post-transcriptionally and assists in mRNA stability, export from the nucleus, and translation initiation, among other functions.