Final answer:
The presence of a really long poly(A) tail on a molecule does not directly activate or inhibit eukaryotic gene expression.
Step-by-step explanation:
The presence of a really long poly(A) tail on a molecule will not directly activate or inhibit eukaryotic gene expression. The poly(A) tail is added to the 3' end of mRNA and serves to protect the mRNA from degradation and signal for export to the cytoplasm. It does not directly impact the activation or inhibition of gene expression. Instead, gene expression is regulated through various mechanisms such as transcription factors and regulatory sequences.