template strand

The template strand is the strand of a gene's DNA that gets read during transcription, base by base, to build a complementary RNA copy. Think of it as the mold or stencil: the RNA is shaped to fit it, so the template dictates the new strand's sequence.

A gene's DNA has two strands, but for any given gene only one acts as the template. RNA polymerase pairs each RNA nucleotide to the template by base-pairing (with U replacing T), so the resulting RNA is complementary and antiparallel to the template — and therefore matches the sequence of the gene's other strand.

That other strand is called the coding (or sense) strand, because it reads the same as the mRNA (apart from T versus U). A common point of confusion: although the template is the one physically read, sequences are usually written down as the coding strand, since that is what spells out the codons of the protein.