Strand representation in the DNA version of the Genetic Code
The sense strand has the same sequence as the transcribed RNA. The antisense strand is read in the other direction. For a particular gene, the sense strand is the genetic code, the other strand is the complementary template used to transcribe the RNA from it. The resultant pre-mRNA molecule (before introns are spliced our) will be single-stranded in the 5’ to 3’ direction with exactly the same sequence as the coding sequence (except for U instead of T). As such, the sense strand is the coding sequence of a gene (as it corresponds directly to the transcribed RNA sequence).

It is important to distinguish the direction of a DNA sequence. Genes can overlap in opposite directions. DNA and RNA molecules can only be synthesised by enzymes in one direction. This is important for DNA synthesis in vivo  (e.g., Okazaki fragments) and molecular biology experiments in vitro (e.g., PCR and NGS). Antisense RNAs are also expressed and are important in regulating cellular functions: this includes enhancers which sometimes express bi-directional RNA and short RNAs involved in RNA interference, microRNA, and CRISPR-Cas).

In molecular, cellular, and computational biology, the sense strand encodes the coding sequence (gene or other transcript). This is the sequence of any resulting RNA. Hence we define a codon as the nucleotide triplet that corresponds to a resulting amino acid. The antisense DNA strand and the tRNAs are complementary to this. Therefore there is an agreed upon convention to determine which strand is “coding” and it is straightforward to derive the resulting amino acid sequence of the encoded peptide given a coding sequence and a start codon (AUG). The antisense strand is the reverse compliment sequence which can also be computed. It is not necessary to store the sequence of both strands of a gene since the coding sequence can be used to infer the sequence of both strands.



See Figure 6-7. Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al. New York: Garland Science; 2002. excerpt online