microRNAs, or miRNAs, are short RNA molecules that regulate gene expression after transcription. Roughly how long is a mature miRNA, and what complex does it join to degrade its target mRNA?

1. MicroRNAs, or miRNAs, are short RNA molecules that are only 21 to 24 nucleotides in length. 2. They are made in the nucleus as longer pre-miRNAs and chopped into their mature form by a protein called dicer. 3. Mature miRNAs recognize a specific sequence and bind to the target RNA. 4. They also associate with a ribonucleoprotein complex called the RNA-induced silencing complex, or RISC, which degrades the target mRNA. 5. 200 to 240 nucleotides is far longer than the length given for a mature miRNA. 6. The initiation complex is instead involved in starting translation, a separate process from miRNA-mediated degradation. 7. The proteasome degrades proteins marked with ubiquitin, which is unrelated to the RISC complex that miRNAs use to degrade RNA. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 16 "Gene Expression", section RNA Stability and microRNAs_