miRNA stands for

• A. microRNA
• B. small interfering RNA
• C. ribosomal RNA
• D. transfer RNA

Answer: (A)

MicroRNA are short noncoding RNA molecules, about 21–24 nucleotides long, that regulate gene expression after transcription. They are produced as longer hairpin transcripts, processed in the nucleus and cytoplasm, and become part of the RNA-induced silencing complex. The mature miRNA guides this complex to target mRNAs by base-pairing with complementary sequences, usually in the 3' untranslated region, leading to reduced protein production either by blocking translation or by promoting mRNA degradation. This sets miRNA apart from ribosomal RNA, which is a structural and functional part of the ribosome, and from transfer RNA, which carries amino acids during translation. It’s also distinct from small interfering RNA, which arises from long double-stranded RNA and typically cleaves nearly perfectly matched mRNA. Therefore, microRNA is the correct name.