question_answer

The hnRNA undergoes post - transcriptional processing in eukaryotes. Mention the two such processes.

Answer:

The precursor of mRNA transcribed by RNA polymerase-II is called heterogenous nuclear RNA (hnRNA). It undergoes following changes

(i) Splicing In this process, the non-coding introns are removed and coding sequences, called exons are joined in a definite order. This process is required because primary transcript contains both introns and exons.

(ii) Capping In this process, an unusual nucleotide (methyl guanosine triphosphate) is added to 5' end of hnRNA.