Negativestrand

Negativestrand, or negative strand, is a term used in genetics and molecular biology to describe the strand of a double-stranded nucleic acid that serves as the template for transcription. In DNA, the double helix comprises two antiparallel strands: the coding or sense strand, which has the same sequence as the resulting RNA (with thymine in place of uracil), and the template or antisense strand, which is complementary to the mRNA and runs 3' to 5'.

RNA polymerase reads the template strand in the 3' to 5' direction and synthesizes RNA in the 5' to 3' direction, producing an RNA transcript that matches the coding strand except for uracil replacing thymine. In this framework, the negative strand is the template for transcription, while the positive or sense strand serves as the reference sequence that is parallel to the mRNA produced.

In the context of RNA viruses, the term negative-sense RNA refers to genomes that are complementary to the viral mRNA. Such viruses must carry or encode an RNA-dependent RNA polymerase to generate positive-sense mRNA before translation. This distinction highlights how the terms positive/sense and negative/antisense are relative to the transcription product.

Nomenclature can be confusing because the labels depend on perspective. The template (antisense) strand is often called the negative strand, whereas the non-template (coding) strand is called the positive or sense strand. Understanding this distinction is important in gene annotation, sequencing, and virology.