<P> A primary transcript is the single - stranded ribonucleic acid (RNA) product synthesized by transcription of DNA, and processed to yield various mature RNA products such as mRNAs, tRNAs, and rRNAs . The primary transcripts designated to be mRNAs are modified in preparation for translation . For example, a precursor mRNA (pre-mRNA) is a type of primary transcript that becomes a messenger RNA (mRNA) after processing . </P> <P> Pre-mRNA is synthesized from a DNA template in the cell nucleus by transcription . Pre-mRNA comprises the bulk of heterogeneous nuclear RNA (hnRNA). Once pre-mRNA has been completely processed, it is termed "mature messenger RNA", or simply "messenger RNA". The term hnRNA is often used as a synonym for pre-mRNA, although, in the strict sense, hnRNA may include nuclear RNA transcripts that do not end up as cytoplasmic mRNA . </P> <P> There are several steps contributing to the production of primary transcripts . All these steps involve a series of interactions to initiate and complete the transcription of DNA in the nucleus of eukaryotes . Certain factors play key roles in the activation and inhibition of transcription, where they regulate primary transcript production . Transcription produces primary transcripts that are further modified by several processes . These processes include the 5' cap, 3' - polyadenylation, and alternative splicing . In particular, alternative splicing directly contributes to the diversity of mRNA found in cells . The modifications of primary transcripts have been further studied in research seeking greater knowledge of the role and significance of these transcripts . Experimental studies based on molecular changes to primary transcripts the processes before and after transcription have led to greater understanding of diseases involving primary transcripts . </P>

Pre-mrna processing (mrna production from pre-mrna) includes which process