Blood
The 3'end of eukaryotic mRNA has a structure of a polyA tail. Magnetic beads with Oligo (dT) are used to perform A-T base pairing with polyA, which can isolate mRNA from total RNA for analysis of transcriptome information. By adding fragmentation buffer, mRNA can be randomly fragmented, and small fragments of about 300 bp can be separated by magnetic bead screening. Under the action of reverse transcriptase, random hexamers were added to reverse synthesize cDNA using mRNA as a template. The double-stranded cDNA structure is a sticky end. Add End Repair Mix to make it a blunt end, and then add an "A" base to the 3'end to connect the Y-shaped linker. At last, the final cDNA libraries were sequenced on the Illumina platform.