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Sense, when applied in a molecular biology context, is a general concept used to compare the polarity of nucleic acid molecules, particularly RNA, to other nucleic acid molecules. Depending on the context within molecular biology, sense may have slightly different meanings.
RNA sense
In virology, the genome of a RNA virus can be said to be either positive-sense, also known as a "plus-strand", or negative-sense, also known as a "minus-strand". In most cases, the terms sense and strand are used interchangably, making such terms as positive-strand equivalent to positive-sense, and plus-strand equivalent to plus-sense. Whether a virus is positive-sense or negative-sense can used as a basis for classifiying viruses.
Viral mRNA is always designated positive-sense, thus it is used as the comparison against the sequence being examined. Positive-sense RNA is taken to mean that a particular viral RNA genomic sequence is identical to the mRNA translated from. As the viral RNA genome is identical to viral mRNA it can be immediately translated by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA polymerase before translation.
DNA sense
Molecular biologists call a DNA strand sequence sense if it is translated or translatable, and they call its complement antisense. It follows then, somewhat paradoxically, that the template for transcription is the antisense strand. The resulting transcript is an RNA replica of the sense strand and is itself sense.
Sense can also be applied slightly differently to the polarity of DNA during viral replication. Positive-sense viral DNA is that which can be used as mRNA to produce functional products such as proteins. Negative-sense viral DNA therefore does not transcribe a RNA molecule that can be used immediately as mRNA, rather it forms a template for the creation of negative-sense RNA genomes.
Ambisense
A genome which contains both positive-sense and negative-sense is said to be ambisense. It can produce different proteins fro the same strand depending upon which direction it is read in.
Antisense mRNA
Antisense mRNA is an mRNA transcript that is complementary to endogenous mRNA, in other words, the non-coding strand complementary to the coding sequence of mRNA. Introducing a transgene coding for antisense mRNA is a technique used to block expression of a gene of interest. Radioactively-labelled antisense mRNA can be used to show the level of transcription of genes in various cell types. Some alternative antisense structural types are being experimentally applied as antisense therapy, with at least one antisense therapy approved for use in humans.
See also
References
- Prescott, L. (1993). Microbiology, Wm. C. Brown Publishers, ISBN 0697013723
- Viral replication and genetics - Google's cache of a page from the International Veterinary Information Service
"Sense (molecular biology)"