Genetics , Genetic Diseases And Molecular Genetics Notes

An Introduction to Genetics, Genetic Diseases & Molecular Genetics Genetic Code 3 nucleotides encode an amino acid - CODON It is degenerate where some amino acids are encoded by more than one codon Codons that specify the same amino acid are called synonyms Is non-overlapping tRNA At least one tRNA for every AA Each tRNA recognises and binds to only one type of AA tRNAGly only binds to glycine 74-93 nucleotides Extensive regions of base pairing secondary structure - clover leaf Contains modified bases Attachment of AA Aminoacyl tRNA synthetase Different synthetase for each type of AA Not just attached but activated Wobble Hypothesis 1st and 2nd base in codon must pair in traditional manner 3rd base in codon is less constrained and can base pair with other bases Ribosome subunits mRNA Aminoacyl tRNAs Protein factors GTP Transcription Reading starts a variable number in from the 5' end until methionine is found Reading stops a variable number in from the 3' end The 1st AA is methionine Protein Synthesis INITIATION ? ELONGATION ? TERMINATION Initiation - Prokaryotes N-formyl Methionine is the initiating amino acid since it has no amine group and therefore cannot form a peptide bond on one side Page 1 

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