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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