QUESTION 1
In a charged tRNA molecule, there are amino acids attached by the 5'-monophosphate terminus. This attachment is catalyzed by aminoacyl-tRNA synthetase, not RNA polymerase. The DHU loop is a part of the tRNA molecule, not a ribozyme.
QUESTION 6
The exons within primary eukaryotic transcripts are joined to form mature mRNA. However, these exons are not conserved in nucleotide sequence and often function as introns in other genes. The number of exons can vary considerably and they are excised during RNA processing.
QUESTION 7
Why couldn't the genetic code be based on a two-base codon? Ribosomes wouldn't function properly, the eukaryotic genome is too large, there are 4 bases in total, and the lack of a third base wobble. Two bases cannot code for all 20 amino acids.