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Specific Disease: For a specific example of the way in which genetic information contained in a particular gene is expressed in an organism, let us consider the case of the human disease sickle-cell anemia. To understand how this disease comes about, one must first look at the function of hemoglobin, which is the protein in red blood cells that picks up oxygen in the lungs and carries it to the body tissues.
A primitive level of viral engineering was already developing specific disease-causing viruses that can control crop-damaging insects or be used as innocuous competitors of natural pathogens (disease-causing organisms). (See Year in Review: AGRICULTURE.) For higher organisms there was as yet no clue as to how to find a specific gene on an intact chromosome of a given cell and replace it with another. Finding the correct one ten-millionth of the total DNA seemed an implausible aim. Because a wide margin of error would be intolerable, direct viral engineering of the human merited little discussion.
Mycoplasmosis is a respiratory disease caused y the bacteria Mycoplasma gallisepticum. It is Iso known as air sac disease or chronic respira-jry disease. Those affected with the disease may how nasal discharge, watery eyes, and respira-)ry difficulty. This disease is often associated /ith other respiratory diseases. It is transmitted hiefly from infected hens to their chicks through le eggs. The disease can also be transmitted by ontact with infected individuals, but it spreads ery slowly in this manner. The disease can best e controlled by maintaining breeding flocks free f the disease by strict measures of isolation and mitation. Chicks hatched from such flocks can egin life free of the disease. |
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