(a) RNA transcript: AUG UGC GGG AUA GGG UUU UGG AGA
(b) Spliced mRNA: AUG UGC GGG GGG UUU UGG
(c) 6 aminoacids are coded by mRNA

Structure of the operon: Each operon is a unit of gene expression and regulation and consists of one or more structural genes and an adjacent operator gene that controls transcriptional activity of the structural gene.
i) The structural gene codes for proteins, rRNA and tRNA required by the cell .
ii) Promoters are the signal sequences in DNA that initiate RNA synthesis. RNA polymerase binds to the promoter prior to the initiation of transcription.
iii) The operators are present between the promoters and structural genes. The repressor protein binds to the operator region of the operon.

The ribosomes of eukaryotes (80 S) are larger, consisting of 60 Sand 40 S sub units. 'S' denotes the sedimentation efficient which is expressed as Svedberg unit (S). The larger subunit in eukaryotes consist of a 23 S RNA and 5Sr RNA molecule and 31 ribosomal proteins. The smaller eukaryotic subunit consist of 18Sr RNA component and about 33 proteins.

Both the strands of DNA are not copied during transcription for two reasons.
1. If both the strands act as a template, they would code for RNA with different sequences. This, in turn, would code for proteins with different amino acid sequences. This would result in one segment of DNA coding for two different proteins, hence complicate the genetic information transfer machinery.
2. If two RNA molecules were produced simultaneously, double-stranded RNA complementary to each other would be formed. This would prevent RNA from being translated into proteins.

In some retroviruses that contain RNA as the genetic material (e.g. HIV), the flow of information is reversed. RNA synthesizes DNA by reverse transcription, then transcribed into mRNA by transcription and then into proteins by translation. This is called reverse transcription.