Micro RNA is transcribed bya) RNA polymerase Ib) RNA polymerase IIc) RNA polymerase IIId) DNA Polymerasee) Drosha
Micro RNA (mi-RNA) are typically 21-25 nucleotides in length and are generated by nucleolytic processing of the products of distinct genes/transcription units. These precursors are single-stranded but have extended intramolecular secondary structure.
Most mi-RNA are processed from RNA polymerase II transcripts of severed hundred to thousands of nucleotides in length called Pri-miRNA (primary transcript). Within these long transcripts are sequency that fold into a hairpin structure. A nuclear RNAase specific for dsRNA called Drosha acts with a nuclear ds-RNA binding protein called DGCR in human (Pasha in Drosophila) and cleaves the hairpin region out of long precursor RNA generating a pre-miRNA.
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