ANTHRO 101 Lecture Notes - Lecture 25: East Los Angeles College, Start Codon, Genetic Code
Document Summary
The genetic code uses three bases to specify an amino acid. Genetic code = translates the sequence of bases in nucleic acids into sequence of amino acids in proteins. Proteins have 20 difference amino acids but dna and rna have 4 bases: three bases specify a single amino acid, mrna triplets = codons (ex. Translation begins with the codon aug the start codon : all proteins originally begin with methionine. Three codons uag, uaa, and uga are stop codons : when the ribosome encounters a stop codon, it releases newly synthesized protein and the mrna. Because all codons have 3 bases, and start & end of a protein are specified, the spaces between codons are unnecessary. Since the genetic codes has 3 stop codons, 61 nucleotide triplets remain to specify only. Most amino acids are specified by several different codons: uua, uug, cuu, cuc, cua, cug = leucine. Transcription consists of three steps: (1) initiation, (2) elongation, and (3) termination.
