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Unformatted text preview: and adjoins adjacent exons Fig. 8.16 Splicing is catalyzed by spliceosomes.
Ribozymes RNA molecules that act as enzymes Ensures that all splicing reactions take place in concert Fig. 8.17 Alternative splicing
Different mRNAs can be produced by same transcript. Rare transplicing events combine exons from different genes. Fig. 8.18 Translation Transfer RNAs (tRNAs) mediate translation of mRNA codons to amino acids. tRNAs carry anticodon on one end. Three nucleotides complementary to an mRNA codon Primary nucleotide sequence Secondary short complementary sequences pair and make clover leaf shape Tertiary folding into three dimensional space shape like an L Structure of tRNA Base pairing between an mRNA codon and a tRNA anticodon directs amino acid incorporation into a growing polypeptide. Charged tRNA is covalently coupled to its amino acid. Many tRNAs contain modified bases Fig. 8.19 a Secondary and tertiary structure Fig. 8.19 b Aminoacyl-tRNA synthetase catalyzes attachment of tRNAs to corresponding amino acid Fig. 8.20 Base pairing between mRNA codon and tRNA anticodon determines where incorporation of amino acid occurs Fig. 8.21 Wobble: Some tRNAs recognize more than one codon for amino acids they carry. Fig. 8.22 Rhibosomes are site of polypeptide synthesis Ribosomes are complex structures composed of RNA...
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