非编码RNA-课件（PPT讲稿）

NAs ). A class of doublestranded RNAs ( dsRNAs ) of ~21 nucleotides in length. siRNAs are produced from longer double-stranded (bimolecular) RNAs or long hairpins, often of exogenous origin , and usually target homologous sequences at the same locus or elsewhere in the genome for destruction (gene silencing), the phenomenon termed RNAi . However, the distinction between miRNAs and siRNAs is ing blurred as both are produced by similar pathways and have similar mechanisms of action . siRNA miRNA miRNA 概念: 概念: miRNA miRNA 是长是长约约 21 21 ～～ 25nt 25nt 的单的单链链 RNA, RNA, 其其中中 50% 50% 定位于易发定位于易发生结生结构改变的染色体区构改变的染色体区域。域。特特点: 点: miRNA miRNA 是内源性的是内源性的, , 是生物体基因是生物体基因的表达产物的表达产物;miRNA ;miRNA 是由不完整的发卡状双是由不完整的发卡状双链链 RNA, RNA, 经经 Drosha Drosha 和和 Dicer Dicer 酶加工而成。酶加工而成。