Question

Answer ALL of the following parts: Question 2: A) In prokaryotes, a small ribosomal subunit can potentially get on an mRNA anywhere it can find enough space to do so. Once a small ribosomal subunit has bound to an mRNA, it will scan along that mRNA in the 5' to 3' direction looking for a start codon at which to initiate translation. How does the small ribosomal subunit distinguish a start codon from any other AUG codon that simply codes for methionine in the middle of a coding sequence? B) Prokaryotic cells can and do produce "polycistronic" mRNAs, which have multiple independent coding sequences coding for separate proteins on the same mRNA strand. Eukaryotic cells don't have polycistronic mRNAs, because only the first (most 5') coding sequence on such an mRNA would ever be translated in a eukaryotic cell. Explain why this is the case - why wouldn't a second, more 3' coding sequence on an mRNA be translated in a eukaryotic cell?

          Answer ALL of the following
parts:
Question 2:
A) In prokaryotes, a small ribosomal subunit can potentially get
on an mRNA anywhere it can find enough space to do so. Once a small
ribosomal subunit has bound to an mRNA, it will scan along that
mRNA in the 5' to 3' direction looking for a start codon at which
to initiate translation. How does the small ribosomal subunit
distinguish a start codon from any other AUG codon that simply
codes for methionine in the middle of a coding sequence? 
B) Prokaryotic cells can and do produce "polycistronic"
mRNAs, which have multiple independent coding sequences coding for
separate proteins on the same mRNA strand. Eukaryotic cells don't
have polycistronic mRNAs, because only the first (most 5') coding
sequence on such an mRNA would ever be translated in a eukaryotic
cell. Explain why this is the case - why wouldn't a second, more 3'
coding sequence on an mRNA be translated in a eukaryotic cell?

Added by Steven T.

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