pierceessentials3e

1.1 Genetics Is Important to Us Individually, to Society, and to the Study of Biology

Albinism among the Hopis illustrates the important role that genes play in our lives. This one genetic defect, among the 20,000 genes that humans possess, completely changes the life of a Hopi who possesses it. It alters his or her occupation, role in Hopi society, and relations with other members of the tribe. We all possess genes that influence our lives in significant ways. Genes affect our height, weight, hair color, and skin pigmentation. They influence our susceptibility to many diseases and disorders (Figure 1.2) and even contribute to our intelligence and personality. Genes are fundamental to who and what we are.

Figure 1.2: Genes influence susceptibility to many diseases and disorders. (a) An X-ray of the hand of a person suffering from diastrophic dysplasia (bottom), a hereditary growth disorder that results in curved bones, short limbs, and hand deformities, compared with an X-ray of a normal hand (top). (b) This disorder is due to a defect in the SLC26A2 gene on chromosome 5.

[Part a: (top) Biophoto Associates/Science Source; (bottom) Reprinted from Johanna Hästbacka et al., The diastrophic dysplasia gene encodes a novel sulfate transporter: Positional cloning by fine structure linkage disequilibrium MAPping. Cell 78(6):1073–1087, 1994. © 1994 Elsevier. Courtesy of Prof. Eric Lander, Whitehead Institute, MIT.]

Although the science of genetics is relatively new compared with sciences such as astronomy and chemistry, people have understood the hereditary nature of traits and have practiced genetics for thousands of years. The rise of agriculture began when people started to apply genetic principles to the domestication of plants and animals. Today, the major crops and animals used in agriculture are quite different from their wild progenitors, having undergone extensive genetic alterations that increase their yields and provide many desirable traits, such as disease and pest resistance, special nutritional qualities, and characteristics that facilitate harvest. The Green Revolution, which expanded food production throughout the world in the 1950s and 1960s, relied heavily on the application of genetics (Figure 1.3). Today, genetically engineered corn, soybeans, and other crops constitute a significant proportion of the food produced worldwide.

Figure 1.3: In the Green Revolution, genetic techniques were used to develop new high-yielding strains of crops. (Left) Norman Borlaug, a leader in the development of new varieties of wheat that led to the Green Revolution. Borlaug was awarded the Nobel Peace Prize in 1970. (Right) A modern, high-yielding rice plant (left) and a traditional rice plant (right).

The pharmaceutical industry is another area in which genetics plays an important role. Numerous drugs and food additives are synthesized by fungi and bacteria that have been genetically manipulated to make them efficient producers of these substances. The biotechnology industry employs molecular genetic techniques to develop and mass-produce substances of commercial value. Growth hormone, insulin, clotting factor, enzymes, antibiotics, vaccines, and many drugs are now produced commercially by genetically engineered bacteria and other cells (Figure 1.4). Genetics has also been used to produce bacteria that remove minerals from ore, break down toxic chemicals, and inhibit damaging frost formation on crop plants.

Figure 1.4: The biotechnology industry uses molecular genetic methods to produce substances of economic value.

Genetics also plays a critical role in medicine. Physicians recognize that many diseases and disorders have a hereditary component, including not only rare genetic disorders such as sickle-cell anemia and Huntington disease, but also many common diseases such as asthma, diabetes, and hypertension. Advances in genetics have resulted in important insights into the nature of diseases such as cancer and in the development of diagnostic tests, including those that identify pathogens and defective genes. Gene therapy—the direct alteration of genes to treat human diseases—has now been administered to thousands of patients, although its use is still experimental and limited.