True or False: The last three nucleotides at the 3' end of tRNA are always CCU.

The statement is false because the last three nucleotides at the 3' end of tRNA are not universally CCU. Instead, they typically include the sequence CCA, which is a conserved feature among most tRNAs across various organisms. This CCA sequence is crucial because it serves as the site for the attachment of the corresponding amino acid, allowing tRNA to play its role in protein synthesis during translation. While there may be variations in specific tRNA molecules due to the specific amino acids they carry, the presence of CCU at the 3' end is not a consistent characteristic across all tRNAs, making the original statement inaccurate. Additionally, the specificity of tRNA can vary between different types and classes based on the amino acids they transport, which further supports the rationale behind the answer choice.