CRNA

Complementary RNA (cRNA) is an RNA molecule that is complementary to a target RNA sequence. In molecular biology, cRNA probes are typically antisense transcripts produced by in vitro transcription from a DNA template that carries a promoter for an RNA polymerase such as T7, T3, or SP6. The resulting cRNA is designed to hybridize specifically to the target RNA under defined conditions, enabling detection or measurement of gene expression.

Production and labeling: A promoter-containing DNA template is transcribed in vitro to generate the cRNA transcript. The RNA polymerase incorporates nucleotides to produce a full-length RNA copy that is complementary to the target. cRNA can be labeled during synthesis with radioactive isotopes or non-radioactive tags (for example biotin or digoxigenin) or labeled after transcription to facilitate detection in downstream assays such as hybridization-based methods.

Applications: cRNA probes are used in in situ hybridization to localize transcripts in tissue or cells, in Northern blot and RNase protection assays to detect specific RNAs, and in microarray workflows where antisense cRNA is produced from total RNA for labeling prior to hybridization. The technique supports qualitative or quantitative analysis of gene expression depending on the protocol.

Notes: cRNA probes require RNase-free conditions and careful design to ensure specificity and minimize cross-hybridization. They are one of several antisense RNA approaches and are distinct from other RNA classes such as circRNA or mRNA used for translation.