Ribosomes Ribosomes were revealed to be the site of protein synthesis in early 1950s(pulse labeling with radioactive amino acids and subcellular fractionations)
Ribosomes were revealed to be the site of protein synthesis in early 1950s (pulse labeling with radioactive amino acids and subcellular fractionations)
Crick's Amino acid H molecule adapter O2C-C-NH3 hypothesis R Amino acid bindi ng site Hydroger . Adapter(tRNA bonds C UIA UGA C UA G UC GG mrNA Nucleotide triplet coding for an amino acid
Crick’s adapter hypothesis Hydrogen bonds
3 Amino acids in a polypeptide chain were found to be coded by groups of three nucleotides in a mrNa Simple calculation indicated that three or more bases are probably needed to specify one amino acid Genetic studies of insertion deletion and substitution mutants showed codons for amino acids are triplet of nucleotides; codons do not overlap and there is no punctuation between codons for successive amino acid residues The amino acid sequence of a polypeptide is defined by a linear sequence of contiguous codons: the first codon establishs a reading frame
3. Amino acids in a polypeptide chain were found to be coded by groups of three nucleotides in a mRNA • Simple calculation indicated that three or more bases are probably needed to specify one amino acid. • Genetic studies of insertion, deletion, and substitution mutants showed codons for amino acids are triplet of nucleotides; codons do not overlap and there is no punctuation between codons for successive amino acid residues. • The amino acid sequence of a polypeptide is defined by a linear sequence of contiguous codons: the first codon establishs a reading frame
mRNA 5'--G U C CUA CG G AU---3 (+) Insertion-GUAG C CUC AC G GA U Altered amino acid sequences Deletion. - UAC C UA C GG A U (平) Insertion and G U AA G CCA CIG G AU deletion Reading frame restored Genetic studies showed that genetic codons are successive triplets of nucleotides
Genetic studies showed that genetic codons are successive triplets of nucleotides Altered amino acid sequences
Nonoverlapping A U ACG AG U C code 1 2 3 Overlapping A UACGAGU C de Amino acid sequence studies of tobacco mosaic virus mutants and abnormal hemoglobins showed that alterations usually affected only one single amino acid: genetic codes are nonoverlapping
Amino acid sequence studies of tobacco mosaic virus mutants and abnormal hemoglobins showed that alterations usually affected only one single amino acid: genetic codes are nonoverlapping