Final answer:
Positions in tRNA not recognized in a sequence-specific manner are mediated by non-specific signals, stemming from phylogenetic or structural aspects, and mutations in the spliceosome recognition sequence can add or delete recognition sites.
Step-by-step explanation:
When positions in a tRNA sequence are not recognized in a sequence-specific manner, such as due to mutations, it is the non-specific signals that mediate them. These non-specific signals may include phylogenetic relationships among tRNAs or general structural characteristics of the tRNA molecule that are conserved across different classes. Notably, mutations can occur in the spliceosome recognition sequence at each end of an intron or exon, or in the spliceosome proteins and RNAs, leading to either the addition or deletion of recognition sites. These changes can influence the intricate interplay between various positions within the tRNA molecule and affect its function. Furthermore, non-random effects seen at almost every tRNA position indicate a higher-order relationship not directly associated with amino acid specificity.