Q. What are the features of hnRNA?
Heterogeneous nuclear RNA (hnRNA) - Primary precursor mRNA transcript made in eukaryotic nucleus are called 'hnRNA,' an abbreviation for 'heterogeneous nuclear RNA. Aspects are as below:
Introns:As many eukaryotic nuclear genes are interrupted by introns, RNA transcripts of intron-containing genes have intronic RNA sequences. Poly A tails at 3'-end: Poly A tails added to 3'-end of most though not all hnRNAs during nuclear RNA processing. These tails are retained in processed mRNA. 5'-Cap structure: A modified GTP is covalently attached to 5'-end of most precursors to mRNA. This cap structure is also retained in processed mRNA. Base Composition and relation to template strand: RNA is synthesized from a DNA template. Sequence of RNA is complementary to DNA template strand and opposite in polarity. C and T in DNA template are transcribed by RNA polymerase as G and A in hnRNA, correspondingly. A and G in DNA template are transcribed as U and C in hnRNA. So mRNA and hnRNA are sequences of A, G, C and U's.