Introns are poorly conserved and of variable length, but the regions at the ends are self-complementary, allowing a hairpin structure to form naturally in the hnRNA; this is the cue for removal by RNA splicing.
Intron 不易保存且长度多变，但在末端区域它能自我互补，并且在hnRNA内行成自然型式的发簪结构，这暗示着RNA剪接后移除。
When gene was transcripted from cell nucleus, the new-synthesized pre-mRNA or hnRNA become mature RNA through a series of responses such as add-cap, splice of pre-mRNA, compose poly-A et al. Then the mature mRNA was transport to cytoplasm.
基因从核内转录后，新合成的pre-mRNA或核异质RNA（hnRNA）通过加帽、pre-mRNA的剪接、合成多聚腺苷酸（PolyA）尾等一系列的反应而成为成熟的mRNA。
Now the functions of Alu elements are still unclear. It is speculated that Alu elements are involved in aspects of gene regulation, e. g. gene rearrangement, CpG methylation, alternative splicing of hnRNA, binding sites of transcription factors and hormone receptors, etc.
目前，对于Alu序列的功能了解得还不透彻，据推测主要与基因调控有关，如基因重排、CpG甲基化、hnRNA选择性剪切、结合转录因子和激素等。