Primary transcript

Primary transcript is the single-stranded ribonucleic acid (RNA) product synthesized by transcription of a gene. In eukaryotes, primary transcripts undergo RNA processing to become mature RNA products such as mRNA, rRNA, and tRNA.

Overview

Primary transcripts are synthesized by RNA polymerase during the process of transcription. The enzyme binds to a specific region of the DNA known as the promoter and begins to synthesize a complementary RNA strand. The resulting primary transcript is a copy of the gene that was transcribed.

In eukaryotes, primary transcripts often undergo several modifications before they become mature RNA molecules. These modifications include 5' capping, polyadenylation, and RNA splicing. The mature RNA products then play various roles in the cell, such as coding for proteins (mRNA), forming the structural and functional core of the ribosome (rRNA), or transporting amino acids during protein synthesis (tRNA).

RNA Processing

RNA processing is a series of modifications that a primary transcript undergoes to become a mature RNA molecule. These modifications are necessary for the RNA to function properly in the cell.

5' Capping

The 5' end of the primary transcript is modified by the addition of a guanosine cap. This cap protects the RNA from degradation and is also important for translation.

Polyadenylation

The 3' end of the primary transcript is cleaved and a poly(A) tail is added. This tail aids in the stability of the RNA and in its export from the nucleus.

RNA Splicing

Introns, or non-coding regions, are removed from the primary transcript and the remaining exons, or coding regions, are joined together. This process is known as splicing.

See Also

• RNA polymerase
• Promoter (genetics)
• 5' cap
• Polyadenylation
• RNA splicing

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