BISC 101 Lecture Notes - Lecture 5: Genetic Code, Transfer Rna, Polyadenylation
21 Nov 2012
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Document Summary
Ribonucleic acid -> ribose sugar with uracil base (not thymine). Dna unwinds, nucleotides are added on the 5" -> 3" direction. Polyadenylation releases polymerase pre-mrna strand site (aauaaa) -> signal -> detaches -> released. Pre-mrna -> mrna: adds 5" cap region. (5" cap region protects mrna from enzymatic degradation), which signals ribosomes to attach, add poly a-trail (aaaa). Inhibits mrna degradation and facilitates mrna out of nucleus. Deletes the introns, joins up the exons (expressed) to produce mrna, which is used in translation. Produces amino acids and joining them together to form a polypeptide (protein). On mrna, the nucleotides are arranges in triplets (triplet code, a. k. a. codons). 3-4 codons may produce the same amino acid. Uaa, uag, uga = 3 stop codons. Most abundant type of rna in cell. Small sub-unit binds to the 5" cap region. Transfer rna (trna) = anti-codon at one end, which is complementary to codon. It carries an amino acid specified by codon usage.
