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RNA Synthesis and Processing


Legend:

Process by which non-coding sequences of base pairs (introns) are subtracted from the coding sequences (exons) of a gene in order to transcribe DNA into messenger RNA (mRNA.)

In chromosomes, DNA acts as a template for the synthesis of RNA in a process called transcription. In most mammalian cells, only 1% of the DNA sequence is copied into a functional RNA (mRNA). Only one part of the DNA is transcribed to produce nuclear RNA, and only a minor portion of the nuclear RNA survives the RNA processing steps.

One of the most important stages in RNA processing isRNA splicing. In many genes, the DNA sequence coding for proteins, or "exons", may be interrupted by stretches of non-coding DNA, called "introns". In the cell nucleus, the DNA that includes all the exons and introns of the gene is first transcribed into a complementary RNA copy called "nuclear RNA," or nRNA. In a second step, introns are removed from nRNA by a process called RNA splicing. The edited sequence is called "messenger RNA," or mRNA.

The mRNA leaves the nucleus and travels to the cytoplasm, where it encounters cellular bodies called ribosomes. The mRNA, which carries the gene's instructions, dictates the production of proteins by the ribosomes.


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