A method for assessing RNA expression, said method comprising: (a) using a reverse transcriptase enzyme to generate cDNA from RNA present within a sample to be assessed for expression of a target RNA, (b) contacting said sample to be assessed for expression of a target RNA with a probe nucleic acid comprising an amplifying restriction endonuclease and a nucleotide sequence complementary to a sequence of a cDNA of said target RNA under conditions wherein, if said cDNA is present in said sample, at least a portion of said cDNA hybridizes to at least a portion of said probe nucleic acid to form a double-stranded portion of nucleic acid comprising a restriction endonuclease cut site, (c) contacting said double-stranded portion of nucleic acid with a recognition restriction endonuclease having the ability to cut said double-stranded portion of nucleic acid at said restriction endonuclease cut site under conditions wherein said recognition restriction endonuclease cleaves said double-stranded portion of nucleic acid at said restriction endonuclease cut site, thereby separating a portion of said probe nucleic acid comprising said amplifying restriction endonuclease from at least another portion of said probe nucleic acid, (d) contacting said portion of said probe nucleic acid comprising said amplifying restriction endonuclease with a signal expansion nucleic acid comprising a label, said amplifying restriction endonuclease, and a double-stranded portion of nucleic acid comprising a restriction endonuclease cut site of said amplifying restriction endonuclease under conditions wherein the amplifying restriction endonuclease contained in said portion of said probe cleaves said signal expansion nucleic acid at said restriction endonuclease cut site of said amplifying restriction endonuclease, thereby separating a portion of said signal expansion nucleic acid comprising said label and said amplifying restriction endonuclease from at least another portion of said signal expansion nucleic acid, and (e) determining the presence or absence of said portion of said signal expansion nucleic acid, wherein the presence of said portion of said signal expansion nucleic acid indicates that said sample contains said cDNA, thereby indicating expression of said target RNA, and wherein the absence of said portion of said signal expansion nucleic acid indicates that said sample does not contain said cDNA, thereby indicating a lack of expression of said target RNA. (a) using a reverse transcriptase enzyme to generate cDNA from RNA present within a sample to be assessed for expression of a target RNA, (b) contacting said sample to be assessed for expression of a target RNA with a probe nucleic acid comprising an amplifying restriction endonuclease and a nucleotide sequence complementary to a sequence of a cDNA of said target RNA under conditions wherein, if said cDNA is present in said sample, at least a portion of said cDNA hybridizes to at least a portion of said probe nucleic acid to form a double-stranded portion of nucleic acid comprising a restriction endonuclease cut site, (c) contacting said double-stranded portion of nucleic acid with a recognition restriction endonuclease having the ability to cut said double-stranded portion of nucleic acid at said restriction endonuclease cut site under conditions wherein said recognition restriction endonuclease cleaves said double-stranded portion of nucleic acid at said restriction endonuclease cut site, thereby separating a portion of said probe nucleic acid comprising said amplifying restriction endonuclease from at least another portion of said probe nucleic acid, (d) contacting said portion of said probe nucleic acid comprising said amplifying restriction endonuclease with a signal expansion nucleic acid comprising a label, said amplifying restriction endonuclease, and a double-stranded portion of nucleic acid comprising a restriction endonuclease cut site of said amplifying restriction endonuclease under conditions wherein the amplifying restriction endonuclease contained in said portion of said probe cleaves said signal expansion nucleic acid at said restriction endonuclease cut site of said amplifying restriction endonuclease, thereby separating a portion of said signal expansion nucleic acid comprising said label and said amplifying restriction endonuclease from at least another portion of said signal expansion nucleic acid, and (e) determining the presence or absence of said portion of said signal expansion nucleic acid, wherein the presence of said portion of said signal expansion nucleic acid indicates that said sample contains said cDNA, thereby indicating expression of said target RNA, and wherein the absence of said portion of said signal expansion nucleic acid indicates that said sample does not contain said cDNA, thereby indicating a lack of expression of said target RNA.