来自于基因组编码的单链RNA前体的小RNA是指[填空1]，源于人工合成或体内的双链RNA前体产生的是[填空2]， 在生殖细胞中表达用于沉默转座子的小RNA是指[填空3]。(Small RNAs derived from genome-encoded single-stranded RNA precursors are referred to as ( ? ), those derived from synthetic or in vivo double-stranded RNA precursors are referred to as ( ? ), and those expressed in germ cells for silencing transposons are referred to as ( ? ).)