Question

describe the formation and function of mRNA, rRNA,and tRNA in prokaryotes and eukaryotes

Answer 1

mRNA: mRNA synthesis occurs inside the nucleus, where RNA polymerase II reads DNA and produce a transcript called mRNA. this process is called transcription. The function of mRNA is to code for proteins or in other words , to translate the genetic information carried in the DNA from which it was transcribed. In prokaryotes, the mRNA is polycystronic, meaning they contain multiple coding sequences (exons) for the coding of multiple proteins. Hence, they have multiple sites for initiation and termination of protein synthesis. But eukaryotic mRNAs are mainly monocistronic, meaning they contain exon for coding single protein .

rRNA: Ribosomal RNA is the component of ribosomes, which is the machinary that catalyses protein synthesis. rRNAs are synthesized in the nucleoli of nuclues. The function of rRNA is to bind to messenger RNA during protein synthesis to ensure that the codon sequences is translated to amino acids correctly.

The smaller subunit of prokaryotic ribosomes has an RNA molecule of about 1500nucleotides long, while larger subunit has two RNA molecules,of which, one is around 3000 nucleotides long and the other is about 120nucleotides long.

In eukaryotes, there are two long RNA molecules,of which ,one is more than 5kb and other around 2kb, and another two which are less than 200 nucleotides in length. Also eukaryotes have an rRNA in the mitochondria and chloroplasts as well.

tRNA: Transfer RNAs are molecules that carry amino acids to the ribosome based on the codon sequence in the mRNA during translation. tRNAs are transcribed by RNA polymerase III in the nucleus as pre-tRNAs.This transcript undergoes extensive modifications both in eukaryotes and prokaryotes. In bacteria, these self-splice, while in eukaryotes, they are spliced by endonucleases.