Transfer RNA - tRNA OR Soluble RNA - sRNA

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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)

Transfer RNA - tRNA OR Soluble RNA - sRNA

Transfer RNA - tRNA OR Soluble RNA - sRNA - After rRNA the second most common RNA in the cell is transfer RNA. It is also called soluble RNA because it is too small to be precipitated by ultracentrifugation at 100,000 g. It constitutes about 10-20% of the total RNA of the cell. Transfer RNA is a relatively small RNA having a molecular weight of about 25,000 to 30,000 and the sedimentation coefficient of mature eukaryote tRNA is 3.8S.

It is made up of 73-93 nucleotides (Rich and RajBhandary, 1976). Each bacterial cell probably contains about a hundred or more different types of tRNA. The function of tRNA is to carry amino acids to mRNA during protein synthesis. Each amino acid is carried by a specific tRNA. Since 20 amino acids are coded to form proteins, it follows that there must be at least 20 types of tRNA.

It was formerly thought that only 20 tRNA molecular types exist, one for each amino acid. It has, however, been shown that in several cases there are at least two types of tRNA for each amino acid. Thus there are many more tRNA molecules than amino acid types. These are probably coded by one gene.

Transfer RNA is synthesized in the nucleus on a DNA template. Only 0.025% of DNA codes for tRNA. Synthesis of tRNA occurs near the end of cleavage stages. Transfer RNA is an exception to other cellular RNAs in that a part of its ribonucleotide sequence (-CCA) is added after it comes off the DNA template. Like rRNA, tRNA is also formed from only a small section of the DNA molecule.

Therefore, it does not show any obvious base relationships to DNA. The tRNA molecule consists of a single strand looped about it self. The 3' end always terminates in a -C-C-A (cytosine- cytosine-adenine) sequence. The 5' end terminates in G (guanine) or C (cytosine). Many of the bases are bonded to each other, but there are also unpaired bases.

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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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