  A system-level genetic code is a hypothetical genetic code that exclusively
or preferentially codes systems of interacting coadapted parts. System-level
genetic codes differ from part-level genetic codes in which each discrete part
is coded independently. In general, a system-level genetic code requires coding
discrete interacting parts such as organs or proteins in an interdependent way.
Changing a single symbol or "gene" in a system-level genetic code affects two
or more parts in a coordinated way. System-level genetic codes provide a
plausible mechanism for evolution by leaps also known as systemic
macromutations or hopeful monsters without invoking an intelligent agent,
vitalistic forces, or new laws of physics. A system-level genetic code may
explain the rapid appearance of new forms of life in the fossil record such as
the Cambrian Explosion in which most invertebrate phyla appeared. A
system-level genetic code may explain the origin of complex integrative systems
of tightly coadapted proteins such as the blood coagulation cascade in which
the removal or structural modification of any single part breaks the system. It
is demonstrated that a simple system-level genetic code can, in principle, be
implemented using biochemical mechanisms similar or identical to the mechanisms
used by transposable elements, regulation of gene expression, and the adaptive
vertebrate immune system. It is further suggested that cancer in the body and
both normal and tumor cell lines cultured in vitro are caused by mutations of
the system-level genetic code. An explanation why multi-cellular organisms
retain the ability to revert to uni-cellularity and thus a tendency to develop
cancer is presented.
