13. a) Explain how the Shine-Dalgano sequence in bacteria helps to locate the st
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Question
13. a) Explain how the Shine-Dalgano sequence in bacteria helps to locate the start codon on mRNA. (2 marks) b) With the help of the codon table below, explain why there is no tRNA with anticodon sequence 5'-UAU-3' in E coli. (2 marks) Second letter UAU Tyrosine uGC UAC UUU Phenyl UCU UUC alanine Serine UGA Stop codon A ULeucine Stop codon Stop codon UGG Tryptophan G UAG CCA ProlineCAC Histidine CCG CAC Histidine GU CAAGlutamine CGG CUU CUG Leucine CCA CGAnine AGU |Asparagine | |serine AUU AI AUA AUG GUU 11 AUC! Isoleucine ||ACC |Threonine li AAC Methionine: ACG start codon AGG Arginine A GUA Valine GCC GCA GAU Aspartic GGU GAC acid GGC GGA Glycine C GUC laine GAA GlutamicSGG GUG GAG acidExplanation / Answer
1) Shine-dalgarno sequence is located around 8 base upstream of start codon AUG. It is a ribosomal binding site in prokaryotes and archaea domains. It helps in recruiting the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon. Because of its location on the mRNA sequence nearby the start codon, it helps in locating it.
2) According to the codon table given below, the initiation or start codon is AUG, hence, the sequence 5'-UAU-3' will have no tRNA in E.coli since translation always starts from AUG which is the initiation codon.
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