Methods for extending polynucleotides

A method of generating cDNA libraries each having an oligonucleotide label, the method comprising the steps of:

• (a) capturing an mRNA by hybridizing the mRNA to capture oligonucleotides attached to one or more solid supports, wherein
• the capture oligonucleotides are complementary to segments of the mRNA, and the capture oligonucleotides are attached to the one or more solid supports by 5′-ends and have 3′-ends with free 3′-O-hydroxyls;
• (b) extending the 3′-ends of the capture oligonucleotides with a reverse transcriptase using the captured mRNAs as templates to form the cDNA libraries on the one or more solid supports;
• and
• (c) synthesizing oligonucleotide labels on cDNAs of the one or more solid supports by template-free enzymatic synthesis;
• wherein:
• said step (a) of capturing includes capturing the mRNA of a single cell or single tissue on the one or more solid supports to form said cDNA libraries that are cell-specific or tissue-specific cDNA libraries, respectively;
• said oligonucleotide labels are unique cell-specific or tissue-specific oligonucleotide barcodes;
• and
• said one or more solid supports include binding compounds attached thereto for capturing predetermined non-nucleic acid ligands.