I am learning RNA-seq analysis. I always encounter this phase "poly(A)+ RNA". After searching, I got this: "Most messenger RNAs contain a poly(A) tail, while structural RNAs do not. Poly(A) selection therefore enriches for messenger RNA. The technique has proved essential for construction of cDNA libraries."
Does it mean that when constructing the cDNA, we always use the ones with a A's tail? Then other RNAs like tRNA are filtered and not used to get their cDNA? I do find some RNAs records on UCSC where microRNAs are included.
When we say poly(A)+ RNA library, what is the difference between normal one? Or normal RNA library is a poly(A)+ RNA library? Thanks.