Expression of Information

Since the nature and structure of DNA is of fundamental importance to its ability to control the form and function of organisms, there appears to be a paradox. If every cell in an organism contains the same genetic information, then why do cells within a plant differ from each other? That is, why is a bark cell so different from a leaf cell?

The answers to these questions stem from the fact that each cell in a multicellular plant contains the same DNA information, but different subsets of this master plan are read in each cell type. For example, a plant has epidermal cells that secrete a protective waxy cuticle, and it also has mesophyll cells that are highly specialized for photosynthesis. The epidermal cells express genes (read DNA sequences) that encode enzymes necessary to build a waxy cuticle. Mesophyll cells, on the other hand, will not express cuticle genes but do express a set of genes that encode enzymes for chlorophyll synthesis. One of the most active areas of biology research today is directed toward understanding how organisms control gene expression.

A cell's environment can influence the set of genes expressed by that cell. Many cellular changes occur as a result of the expression of new sets of genes induced by hormones (see Chapter 11). We know, for example, that an epidermal cell expresses genes for cell elongation if the hormone auxin is present; when mesophyll cells are moved from dark into light, many dramatic changes in gene expression also occur.

Stern-Jansky-Bidlack: I 13. Genetics I Text I I © The McGraw-Hill

Introductory Plant Biology, Companies, 2003

Ninth Edition

Stern-Jansky-Bidlack: I 13. Genetics I Text I I © The McGraw-Hill

Introductory Plant Biology, Companies, 2003

Ninth Edition

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