BIOL 222 Lecture Notes - Lecture 14: Exonuclease, Intron, Base Pair
Document Summary
Biol 222 lecture 14 rna processing. 5" methyl cap - added to the mrna (5" to 5" linkage with a triphosphate in between: protection and translation, protects rna from exonuclease, the exonuclease does not recognize the 5" cap. Poly a tail - added to the 3" end, a long string of adenines: mrna stabilization, translation initiation, in prokaryotes poly a tail targets mrna for degradation. Splicing removes introns (intervening sequence: introns non protein coding sequences, exons protein coding sequences, splicesosome consisting of small nuclear ribo-nuclear protein complexes (snrnps) Snrnp = snrna + protein: introns allow rapid generation of new genes by exon shuffling, thus new protiens, exon shuffling provides genetic diversity. Several srnas function as regulators: not translated into proteins. Eukaryotes: rna interference (rnai, mechanism used to limit invasion of foreign genes and for regulating eukaryotic gene expression, triggered by dsrna that arises via transcription, dicer cleaves dsrna.
