Final answer:
siRNAs and miRNAs function primarily in RNA interference, a process involved in post-transcriptional regulation that leads to gene silencing by binding to mRNA and preventing its translation.
Step-by-step explanation:
siRNAs and miRNAs are involved in the process known as RNA interference (RNAi), which plays a crucial role in gene regulation. These small noncoding RNAs bind to mRNA to prevent translation, effectively silencing gene expression. siRNAs are typically completely complementary to their target mRNA, while miRNAs are mostly complementary. Both participate in the post-transcriptional regulation of gene expression by promoting degradation or inhibiting the translation of messenger RNA.