Question

would the first one be D and the second one C?

"The processing of some tRNA molecules, like that of most mRNA molecules, involves the addition of a poly-A tail at their 3' end the addition of a poly-A tail at their 5' end the addition of a CCA sequence at their 5' end the addition of a CCA sequence at their 3'end the alternative deletion of random segments splicing

Answer 1

1. The tRNA processing involves 5 steps. These include cleaving off the 5' leader sequence and the 3' end of pre - tRNA is cleaved off. At the terminated 3' end in some bacteria andarchaea the pre-tRNAs already contain the CCA codon in their transcript immediately upstream of the 3′ cleavage site and these do not require addition of codon and in bacteria which do not contain CCA codon, it is added. The CCA at the 3′ end of the mature tRNA is the site at which the amino acid will be added. Other changers include chemical modifications of multiple nucleotides of pre tRNA and splicing of the introns in eukaryotic and archaeal pre tRNAs. Therefore, the option D is correct.

2. The mRNA synthesized during the transcription is called pre-mRNA and it should undergo post transcriptional processing to become a matured mRNA. The pre-mRNA contains several noncoding sequences called introns. These are removed by splicing and all coding sequences or exons are joined to form a mature mRNA that produces a polypeptide. Thus, the presence of introns makes the pre - mRNA long and bigger in length than mature mRNA. Similarly the immature rRNA is also long molecule that is cleaved off into small RNA fragments of varying length. Therefore, the immature or pre-mRNA or primary mRNA and immature rRNA are longest RNAs produced in eukaryotes. The options C and D are correct.