Figure 1.1. Gene expression.

Figure 1.1

Gene expression. A gene’s DNA is transcribed into mRNA which is, in turn, translated into protein. The functional components of a gene are schematically diagramed here. Areas of the gene destined to be represented in mature mRNA are called exons, and intervening areas of DNA between exons are called introns. The portion of the gene that controls transcription, and therefore expression, is the promoter. This control is exerted by specific nucleotide sequences in the promoter region (so-called “cis”-acting factors) and by proteins (so-called “trans”-acting factors) that must interact with promoter DNA and/or RNA polymerase II in order for transcription to occur.

The primary transcript is the RNA molecule made by RNA polymerase II that is complementary to the entire stretch of DNA containing the gene. Before leaving the nucleus, the primary transcript is modified by splicing together exons (thus removing intron sequences), adding a cap to the 5´ end, and adding a poly-A tail to the 3´ end. Once in the cytoplasm, mature mRNA undergoes translation to yield a protein.

From: Chapter 1, Molecular Biology

Cover of Holland-Frei Cancer Medicine
Holland-Frei Cancer Medicine. 5th edition.
Bast RC Jr, Kufe DW, Pollock RE, et al., editors.
Hamilton (ON): BC Decker; 2000.
© 2000, BC Decker Inc.

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