23.Some synthetic biologists have proposed the creation of an entirely new, free-living organism with a minimal genome—the smallest set of genes that allows for replication of the organism in a particular environment. This genome could be used to design and create, from “scratch,” novel organisms that might perform specific tasks such as the breakdown of toxic materials in the environment.

24.The genome of the fruit fly Drosophila melanogaster was sequenced in 2000. However, this “completed” sequence did not include most heterochromatin regions. The heterochromatin was not sequenced until 2007 (Hoskins et al. 2007. Science 316:1625–1628). Most completed genome sequences do not include heterochromatin. Why is heterochromatin usually not sequenced in genome projects? (Hint: See Chapter 8 for a more detailed discussion of heterochromatin.)