BIOL 3090 Midterm: BIOL 3090 Test 3 Lecture Notes (Got A+ on the test)
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Start codons: synthesis of almost all polypeptide chains in prokaryotes and eukaryotes begins with met. (almost always the aug codon), occassionally gug in some bacteria mrnas. (also codes for valine, occasionally cug in eukaryotes. (also codes for leucine) Table 4 1: only met(aug) and trp(ugg) are encoded by single codons. (aug and ugg respectively, aug (encoding met) is used as the translation start codon (and wherever met is encoded within the mrna, notice that upon rare occasion, cug and gug encode the initial met, notice that when several codons encode a single amino acid, the codons differ in the third position (gly, pro, thr, ser, ala) Dna replication: dna synthesis proceeds 5" to 3", chain growth results from formation of phosphodiester bond between 3"o of growing strand, unlike rna polymerase, dna polymerase cannot initiate chain synthesis without a pre existing and phosphate of a dntp.