Polycistronic and monocistronic RNA

Molecular biology

1. Polycistronic & Monocistronic RNA INDRANI KAR M.Sc Microbiology St. George College of Management & Science Bengaluru North University

2. INTRODUCTION RNA usually exists as single stranded polypeptid, and uracil is present insead of thymine in RNA single strand. In bacteria there are 3 type of RNA present as ribosomal RNA, transfer RNA and masses RNA. Ribosomal RNA are made of by ribosomal subunits, massenger RNA almost are many types ,transfer RNA is of 50 different types. All of these three molecules resembles the single stranded structure of the DNA, intramolecular and have some double strands regions.

3. C o ntinue . . . . . Typically one half and two third of bases in RNA are paired, the pairing regions are short containing six or fewer bases. RNA is also hydrolyzed to free nucleotides either chemically or enzymatically, at pH1 the phosphodiesters bond and the N-glycosidic bond between the sugars and bases are broken, releasing the free bases. Some nuclease cleave only at the end of a nucleic acid, either the 3' or the 5' terminus, removing the single nucleotide or short oligonucleotides.

4. T r a n s f e r R NA ( t - R N A ) Transfer RNA binds to the amino acids to the ribosome and start translation, it carries the amino acids and binds to the messenger RNA. In primary structure it contact about 73 to 93 nucleotides, three anticodon and all 4 bases are methylated. In the secondary structure it is look like cloverleaf structure, forms base pairs loops, anticodon and fragments strands. In the tertiary structure it is formed as L shape structure, three dimensional structure form D loop.

5. R i b osomal R NA ( r - R N A ) Ribosomal RNA is a fibricate part of the polypeptide and provides mechanisms for decoding m-RNA and interacts with tRNA during translation. Ribosomal RNA is a structure component of the ribosome and actually found in the catalytic element for proteins synthesis. It's most abundant type of RNA in the cell, it compromises the large and small subunit. Prokaryotic RNA is 70 svedberg unit, a unit of the measurement for the sedimentation coefficient or how fast molecular sediment when centrifuged.

6. R i bosomal RNA

7. Mes s enger RNA ( m - R N A ) Messenger RNA is the blue print of protein reproduction, transcribed from the DNA, transfer the information from cell to nucleus. Transfer of the information is done into protein nucleotides, that can in codon as genetic information. Genetic codon are triple bases nucleotides, each codons corresponding to the specific amino acids, sequence of codon ends with the a codon that is stop single. The protein synthesis process requires transfer RNA (t-RNA) for transferred the information. The m-RNA makes up to only only about 5% of the different types of RNA found in both prokaryotic and eukaryotic.

8. T y pe of messenger RNA P o l y c i s t r o n i c mes s e n ger RNA M o n o c i s t r o n i c mes s enger R NA

9. P o l y c i s t r o n i c me ssenger RNA The messenger RNA is translated into amino acids by protein synthesizing machinery of the cell. In the prokaryotes the messenger RNA molecules often contain information for the amino acids sequence of each different polypeptides chain, in these case such molecules are called polycistronic messenger RNA. In polycistronic messenger RNA the cistron is used as the synonymous of the gene ---- a base sequence encoding a single polypeptide chain. The gene that contain polycistronic messenger RNA molecules are often encode different types of proteins of a metabolic pathway. For example S. typhimurium.

10. C o n tinue . . . . . In the cell of S. typhimurium 10 enzymes needed to synthesize histidine are encoded only one messenger RNA molecule. The use of polycistronic messenger RNA is an economical way for a cell to regulate synthesis of related proteins in a coordinated way. The prokaryotes are the examples of the synthesis of the messenger RNA molecule, the synthesis of the several related molecules. With the polycistronic messenger RNA the synthesis is regulated by the single signal made at the same time is called coordinate regulation.

11. C o o r dinate r e gulations

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