Illumina mRNA-seq protocol

[Xi Wang]

Hi all,

I found in the Illumina mRNA-Seq protocal that usually only ~200bp frangments are sequenced. Since random priming could synthesize cDNA fragments from anywhere of the mRNA fragments, if the synthesized cDNA fragments are much shorter than 200bp, the cDNA fragments will be filtered out by gel selection, and thus those positioins of transcripts can never be sequenced. Is my understanding right? And if so, this sample preparing would introduce bias, right?

Thanks in advance.