What is antisense RNA, how is it produced, and what uses can it have?

Are you are referring to RNA interference e.g by microRNA (miRNA)? MiRNA are small (18-30 nt) anti-sense RNA that can be used for posttranscriptional regulation of genes that the RNA is complementary to. MiRNA are first synthesized as long RNA strands which is then cleaved to about 60 nt by the endonuclease drosha in the nucleus. The cleaved strand is then transported to cytoplasm where it is cleaved by a dicer endonuclease to form the mature miRNA (18-30 nt). This miRNA is then incorporated into an RNA-induced silencing complex (RISC) protein, which then directs this complex to target RNA. Binding of miRNA causes tartget mRNA to be degraded or inhibits translation. Example of miRNA posttranscriptional control is in regulation of LPS-mediated innate immune responses (TLR4 --- NF kappa B signalling) by targeting TRAF6 and IRAK1 mRNA.