Compositions and kits for molecular count

A method for counting the number of occurrences of a target mRNA molecule in a sample comprising: (a) providing a plurality of oligonucleotide markers, in which a oligonucleotide tag of the plurality of oligonucleotide markers comprises a target-specific sequence, a sequence exclusive identifier and a primer sequence optional universal PCR, and wherein the target-specific sequence comprises a sequence oligo dT; (B) combining a sample comprising a target mRNA molecule it comprises a polyA sequence with the plurality of oligonucleotide markers so that the sequence oligo dT oligonucleotide tag hybridizes to the polyA sequence of the target mRNA molecule to form an mRNA molecule labeled, in which each target mRNA molecule can hybridize with a different oligonucleotide tag, and wherein the unique identifier region uniquely identifies occurrences of the target mRNA molecule; (C) synthesizing a copy of the target mRNA molecule labeled by reverse transcription to form a DNA molecule labeled, wherein at least a portion of the oligonucleotide tag acts as a primer for reverse transcription reaction, and wherein the molecule labeled DNA comprises a copy of the target mRNA molecule and oligonucleotide tag; (D) detecting the labeled DNA molecule, a complement of the DNA molecule labeled, a reverse complement of the DNA molecule labeling or a portion thereof; and (e) determining a count of different DNA molecules labeled and have, thus, the number of occurrences of a target mRNA molecule in the sample.