Synthetic Biology - Brutes or Angels: Human Possibility in the Age of Biotechnology - page 256

in the second part of this chapter we will consider whether differences
between genetic engineering and synthetic biology—the kinds of life forms
created, their underlying objectives, and their differing views of nature—
demand new ethical thinking for the era of synthetic biology.
How Synbiologists Do Synthetic Biology
There are two basic approaches to doing synthetic biology: top-down (fig.
10.2) and bottom-up (fig. 10.3). The top-down approach uses DnA seg-
ments or genes with known functions and arranges them in creative ways
to design new life forms with properties useful to at least some humans.
Top-down synbiologists insert extensive swaths of creatively combined
pieces of DnA into existing cells. The inserted DnA may be a mixture of
genes from several other organisms, or it may be completely artificial—
envisaged by humans and made by a DnA-synthesizing machine. one ac-
tive area of top-down research is developing host cells whose own genomes
are pared down to facilitate acceptance of the new DnA and acquisition of
correspondingly new cellular life styles.
Bottom-up synthetic biology aims to create new life forms from scratch
using readily available chemicals. Bottom-up synthetic biology is not yet a
reality, but if and when it arrives, both the genetic information (DnA or
some new type of genetic information-carrying mole cule ) and its cellular
containers will be wholly human-made. Both top-down and bottom-up
synthetic biology make humans the creators of brand-new forms of life that
are dramatically different from nature's products of biological evolution.
Examples of top-down synthetic biology. Assembling a large collection of
“standard biological parts” (sBPs) is the project of a research group at mas-
sachusetts institute of Technology (miT). An sBP is a well-deined seg-
ment of DnA with a known function in living cells. some thirty-ive hun-
dred sBPs now stored in super-cold freezers comprise miT's registry of
standard Biological Parts and are available to synbiologists worldwide. 5
sBPs are categorized under headings that reflect collaborations between
biologists, physicists, and engineers: e.g., measurement, reporters, invert-
ers, protein generator, protein coding, regulatory, tags, signaling, com-
posite devices, and terminators. The idea is to mix and match the parts