Invariant and Semivariant Nucleotides

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Ribose Nucleic Acids Comparison Between DNA and RNA Ribosomal RNA (rRNA) Characteristics of Different Ribosome Types Types of rRNA Synthesis of rRNA Messenger RNA (mRNA) Size of mRNA Structure of mRNA Stability of mRNA Synthesis of Messenger RNA - mRNA Polyadenylation Capping in mRNA Methylation in mRNA Heterogenous Nuclear RNA (hnRNA)

Invariant and Semivariant Nucleotides

Invariant and Semivariant Nueelotides - Different types of tRNAs contain several nucleotides located in the same relative position. These include both invariant and semi-variant residues. Fifteen invariant residues are present in almost all tRNAs (except initiator tRNA) taking part in protein synthesis.

These are nucleotides of A, C, U, G, T and ψ. Their positions are indicated by the numbers after the letters: U8, A14, G18, G19, A21, U33, G53, T54, ψ55, C56, AS8, C61, C74, C75 and A76. Some of these residues may undergo modifications in tRNAs from certain sources. Thus G18 may be Gm in certain tRNAs.

Eight semi invariant residues present in almost all tRNAs are Y11, R15, R24, Ya32, H37, Y48, R57 and Y60. Here R represents purines, Y pyrimidines, and H the hypermodified purine nucleoside on the 3' side of the anticodon.

n addition, with certain exceptions, most tRNAs contain R9, G10 or modified GI0 and R26' In the D stem Y11 and R24 are correlated invariants which form a Waston-Crick base pair. Thus the Y11-RZ4 pairing is almost always either C-G or V-A. Another pair of correlated invariants is RIS and Y 4s'.

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Difference Between Prokaryotes and eukaryotes mRNA Transfer RNA (tRNA) OR Soluble RNA (sRNA) Structure of Transfer RNA - tRNA Unusual Bases in tRNA Classification of tRNA Invariant and Semi invariant Nucleotides Tertiary Structure of tRNA Initiator tRNA Specificity of tRNA Biosynthesis of tRNA Comparison of Different Types of RNA

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