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translation initiation - scannning of mRNA by ribosome machinery (Dec/03/2005 )

How does the ribosome machinery scan for the translation initiation site
does the transcription initiation site need to be in frame with the translation initiation site
what happens if the ribosome machinery encounters stop codons in mRNA while scannin from the first base of the mRNA to the translation initiation site

I am new to this field and was wondering about these questions


No, the transcription start does not have any frame-like relationship to the translation start. Stop codons play no role in the identification of the translation start site. There are riboosomal binding sites 5' of the translation start which are important in identifying the correct tranlation start site. If you are working with prokaryotes, these are Shine-Dalgarno sequences; for eukaryotes, Kozak sequences.