Regulation of Gene Expression

Regulation of gene expression is as important as gene function. The last page described how DNA codes for proteins, which perform actions like making hair or carrying oxygen in our blood. Imagine if we grew hair in our mouths, or teeth on our heads. In order to avoid such mishaps, all genes are regulated. Contained within our DNA sequence are elements known as promoters and repressors that allow individual cells to control which genes are expressed. This is how the individual cells in our bodies know which genes to use. There are genes specific to each tissue (muscle, brain, liver, etc.) in our bodies as well as "housekeeping genes" which are present in all cells. Expressing genes in the appropriate tissue at the appropriate time is very important. Cancer, defined as any uncontrolled growth, is ultimately a result of misregulation of gene expression.

Genes may be expressed in specific locations (eg. tissue-specific genes), at specific times (eg. embryo-specific genes), or in response to environmental stimuli (eg. light-responsive genes). Viruses are powerful genetic engineering tools because of their ability to target specific tissues and express specific genes in those tissues. One of the reasons that herpes virus is potentially useful for treating brain diseases because it infects brain cells and expresses specific genes in brain cells. The challenge is to disable the herpes-causing genes while introducing functional beneficial genes.

The next page outlines how one might go about genetically engineering glow-in-the-dark houseplants.

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