This document discusses different types of RNA, including messenger RNA, transfer RNA, and ribosomal RNA. It describes: 1) Messenger RNA carries genetic information from DNA in the nucleus to the cytoplasm for protein production. Messenger RNA can be polycistronic, containing information for multiple proteins, or monocistronic, containing information for a single protein. 2) Transfer RNA transports amino acids to the ribosome during protein translation based on the messenger RNA code. It has a cloverleaf secondary structure and L-shape tertiary structure. 3) Ribosomal RNA is a structural component of ribosomes and facilitates protein synthesis by decoding messenger RNA and interacting with transfer RNA. It comprises the large and

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.

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• 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.

6. Transfer RNA ( t-RNA )
• 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.

8. Ribosomal RNA (r-RNA)
• 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.

9. Ribosomal RNA

10. Messenger RNA (m-RNA )
• 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.

12. Type of messengerRNA
1.Polycistronic messenger RNA
2.Monocistronic messenger RNA

13. Polycistronic messenger 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.

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• 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.

16. Coordinate regulations

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