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When a DNA sequence is presented in
scientific journals and databases, it is usually written as a single
strand. By convention, the strand shown is the coding (+) or sense
strand, identical in sequence (with T's instead of U's) to its mRNA
copy. The mRNA then serves as a template for translation, its 5'
or upstream sequence (beginning with AUG) corresponding to the NH3-terminal "Met" of
the protein.
5' - ATGCTAAAATCG- 3' DNA coding (+) strand
5' -AUGCUAAAAUCG- 3' mRNA or sense strand
NH3-met-leu-lys-ser-CO2- protein
The complementary DNA strand is called the noncoding
or (-) strand and corresponds to the antisense strand. In order to
hybridize with and thus detect a specific mRNA, the probe must consist
of complementary antisense sequence. Antisense RNA probes are generated
when an RNA phage promoter adjacent to more downstream sequence is
used. |