6. Many trinucleotides were found to promote the binding of specific aminoacyl-tRNA to ribosomes It was discovered in 1964 that a specific aminoacyl- trna would bind to the isolated ribosomes when the corresponding synthetic polynucleotide messenger or only the trinucleotide is present many genetic codes were revealed by examining which aminoacyl-tRNa is bound to the ribosomes mixed with specific trinucleotides using filter binding assay
6. Many trinucleotides were found to promote the binding of specific aminoacyl-tRNA to ribosomes • It was discovered in 1964 that a specific aminoacyltRNA would bind to the isolated ribosomes when the corresponding synthetic polynucleotide messenger or only the trinucleotide is present. • Many genetic codes were revealed by examining which aminoacyl-tRNA is bound to the ribosomes mixed with specific trinucleotides using filterbinding assay
Radioactive amino acid The filter-binding assay Trinucleotide for detecting the binding Ribosome of a trinucleotide to a Filter specific aminoacyl-trNA molecule about 50 codons were assigned by L this simple and elegant method val
The filter-binding assay for detecting the binding of a trinucleotide to a specific aminoacyl-tRNA molecule: about 50 codons were assigned by this simple and elegant method
7. Polyribonucleotides of defined repeating sequences of two to four bases helped to end the decoding work Khorana successfully developed a method to synthesize polyribonucleotides of defined repeating sequences using a combination of organic synthesis and enzymatic techniques Polypeptides synthesized using these polyribonucleotides had repeating one to a few amino acids Sequences for specific genetic codes can be determined by comparing the information obtained here and those obtained by using rNAs having random sequences made from two nucleotides of determined ratio
7. Polyribonucleotides of defined repeating sequences of two to four bases helped to end the decoding work • Khorana successfully developed a method to synthesize polyribonucleotides of defined repeating sequences using a combination of organic synthesis and enzymatic techniques. • Polypeptides synthesized using these polyribonucleotides had repeating one to a few amino acids. • Sequences for specific genetic codes can be determined by comparing the information obtained here and those obtained by using RNAs having random sequences made from two nucleotides of determined ratio
Copolymer of repeating dinucleotides always lead to synthesis of polypeptides of repeating dipeptides ABAbababababaB aa1---aa2---aa1---aa Template Product Codon assignments Poly(uc) Poly(Ser-Leu)UcU→ Ser CUC→Leu Poly(AG) Poly(Arg-G|u)AGA→ Arg GAG→→Glu Poly(AC) Poly(Thr-His) ACA Thr CAC His
Copolymer of repeating dinucleotides always lead to synthesis of polypeptides of repeating dipeptides: ABABABABABABAB-- aa1 ---aa2 ---aa1 ---aa2 ----
Copolymer of repeating trinucleotides will lead to the synthesis of three homopolypeptides Start POR: POR: PQR: PQR: PQR: PQR aa aa-aaraalaa1aal Start P: QRP: QRP:QRP: QRP:ORP: QRP aaz-aaz-aa2-aa2-aa2-aa2 Start PQ: RPQ:RPQ: RPQ: RPQ: RPQ: RPQ aa3-a83aa2-aa3-aa3-a83
Copolymer of repeating trinucleotides will lead to the synthesis of three homopolypeptides: