What Is Biotechnology? - Biotechnology and Your Health: Pharmaceutical Applications - page 2

To make bread, after the dough is kneaded to make the gluten
(flour protein) stringy, the dough is kept at a warm temperature to
allow the yeast cells to multiply in number. The yeast cells need
energy to grow, so they break down sugars in the flour to CO 2 ,
creating pockets of gas. This gas makes the dough rise. When the
bread is baked, the gluten dries out and the bread is filled with
many small holes.
Wine makers grow yeast submerged in liquid grape pressings.
This deprives the yeast of oxygen so that it produces ethanol as a
waste product when it metabolizes sugar. A slightly more compli-
cated process is used to make beer, but the principle also involves
growing yeast cells without oxygen so that they produce ethanol as
they make energy.
Cheese is also made through biotechnology. Rennin, a protein
found in the stomachs of young cows, is added to milk to make
cheese. (Today, rennin is usually made with modern biotechnology
methods.) The rennin breaks down casein, the major protein of
milk, into small pieces. Then, cheese makers add bacteria to milk
to convert (ferment) the lactose sugar in the milk to acid, which
causes the casein fragments to curdle, making them form semi-solid
lumps. The flavor of cheese becomes more intense as it ages, and the
flavors concentrate. Adding certain molds during the aging process
turns cheese blue in color.
DEVELOPING THE TOOLS AND METHODS
OF MODERN BIOTECHNOLOGY
Mendelian Genetics
Modern biotechnology, defined as the movement and modification
of genes at will, was built on discoveries in genetics and biochem-
istry originally made in the first half of the 20 th century. Scientists
learned that inherited characteristics or traits, such as hair or eye
color, are passed from parents to offspring in units of inheritance
called genes. You may have learned how an Austrian monk named