Figure 1.

Standardized definitions for Watson and Crick strands. Sensu stricto, a genomic reference is used, like a submetacentric centromere (gray bar), to define two unequal arms of a chromosome. The Watson strand is the strand of a chromosome that has its 5'-end at the short-arm telomere and its 3'-end at the long-arm telomere. The Crick strand is the strand of that has its 5'-end at the long-arm telomere and its 3'-end at the short-arm telomere. If a chromosome is oriented differently, the designations still apply, providing much needed terminological consistency. The Watson strand should be stored as the reference (+) strand in a genomic database. Usage of the terms "Watson strand" and "Crick strands" are discouraged outside of a genomic context. If no genomic reference is possible, then it is acceptable to use these terms sensu lato, where the Watson strand is simply a database's reference strand, and the Crick strand its complement.