tRNA Structure - extra arm . In class I tRNAs the extra arm...

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tRNA Structure -Small, ~ 70-90 ribonucleotides long (remember, they are transcribed from certain DNA sequences) -Single-stranded but folded into a particular 3D shape ( Fig. 2 ). The 3D shape is held together by intrachain hydrogen bonds between complementary base pairs ( Fig. 1 ). Like all RNA molecules, they have a 3'-OH terminus, but the opposite end terminates with a 5' monophosphate rather than a 5'-triphosphate, because tRNA molecules are cut from a large primary transcript. see Figure of tRNA in text book (P. 274-275) Note the D arm which contains dihydrouracil , the T psi C arm which contains a thymine, a pseudouridine, and a cytosine. Also note the presence of the
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Unformatted text preview: extra arm . In class I tRNAs the extra arm is quite small, in class II RNAs the extra arm is long. Note the 4 regions of molecule where you have intrastrand hydrogen bonding. Note the location of the anticodon . The anticodon is a sequence of 3 bases that can form base pairs with a codon sequence in the mRNA ( Fig. 3 ). No tRNA has anticodon complementary to stop codons UAG, UAA, or UGA tRNAs are initially made as part of a somewhat longer RNA transcript. First cut out, then completed by an enzyme that adds the three nucleotides CCA to the 3'end. Note that the 3' ribonucleotide base is ALWAYS adenine ....
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This document was uploaded on 11/03/2011 for the course BIOLOGY MCB2010 at Broward College.

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