Why make three different mRNAs that all produce the same protein?

1.Why make three different mRNAs that all produce the same protein?
2Exercise/Discussion topic: In the Nucleotide database, type in:

16S
RNA
16S RNA
“16S RNA”
16S AND RNA

What is the preferred phrase for 16S and RNA?

3.( MeSH)Try entering “aminotransferase.” What is the preferred term? Limit to the subheading “drug effects.” Now search PubMed. How many records?

4.Exercise/Discussion topic: List number of PubMed records:
smith j
smith j AND hopkins [AD]
smith j AND ohio [AD] AND state [AD]

What field does [AD] limit to? What might you miss by using this limit?