The sequence in mRNA that complements the DNA template is called the coding strand. It is the strand of mRNA that is complementary to the template strand of DNA. The template strand is the strand of DNA that is used as a template for the synthesis of mRNA. The coding strand is the strand of mRNA that is actually translated into protein.

The coding strand of mRNA is complementary to the template strand of DNA in that the bases on the mRNA strand are complementary to the bases on the DNA strand. For example, if the template strand of DNA has the sequence 5'-ACTGATC-3', then the coding strand of mRNA will have the sequence 3'-UGACUAG-5'.

The coding strand of mRNA is important because it is the strand of mRNA that is actually translated into protein. The ribosome reads the sequence of bases on the coding strand of mRNA and uses this information to synthesize a protein. The sequence of bases on the coding strand of mRNA determines the sequence of amino acids in the protein.