Cells and Molecules - Brutes or Angels: Human Possibility in the Age of Biotechnology - page 14

ies end up jammed into glove boxes of workers' cars and trucks and are
eventually discarded.
in this analogy, blueprints are DnA molecules, copies of the blueprints
are mrnA molecules, and the cathedral is a cell or an organism built from
an assemblage of proteins. The workers are ribosomes, machines that pro-
duce proteins using the instructions in mrnA. The architect is natural se-
lection, the force driving most of evolution. not included in the analogy is
how mutation and the recombining of genetic material during sexual re-
production produce variations in a population of blueprints upon which
natural selection acts during evolution.
To appreciate the power of some of the biotechnologies we'll be exam-
ining, such as embryo selection (chapter 3), genomics (chapters 4 and 5),
genetic enhancement (chapter 6), and synthetic biology (chapter 10), we
need some basic information about the three components of the central
dogma: DnA, rnA, and protein. so, we look at the structure of these
three types of molecules, beginning with proteins. Then we examine how
genetic information flows inside a living cell, from DnA through rnA to
proteins. finally, we consider how genetic information is passed on be-
tween successive cell generations and between successive generations of
in di vidu als.
Proteins
Proteins (strings of attached amino acids ) are among the largest molecules
in the cell. They are long, linear molecules that fold and bend to acquire
complicated three-dimensional shapes (fig. 1.6). one way to classify a pro-
tein is on the basis of its function: structural, catalytic, regulatory, or nu-
tritional. structural proteins produce structures inside the cell like micro-
tubules or substances secreted by cells such as hair or mucus. Catalytic
proteins are also called enzymes. They make it possible for the thousands
of biochemical reactions inside a cell to occur at the rapid rates required
to maintain life. regulatory proteins help an organism to adjust the reac-
tions occurring inside its cells in ways appropriate for the various inter-
nal and external conditions confronting the organism. for example, hor-