William Tivol tivol at
Wed Dec 6 14:37:09 EST 1995

Emerson V.P.A. (rory1 at wrote:
: What are non-communicable diseases?

: What is the beginning of the life cycle?

Dear Emerson,
	An example of a non-communicable disease would be sickle-cell disease.
This (or other non-communicable diseases) cannot be transferred from one per-
son to another by contact between persons.  Sickle-cell disease is genetic in
origin, so the only way to transfer it is to pass along the gene.  There are
more complicated examples (such as MS) where predisposition factors and ex-
posure factors seem to be required in combination.
	Since a cycle has no beginning, the selection of the beginning of a
life cycle can be somewhat arbitrary; however, often there is an obvious point
to define as the beginning.  Usually the beginning of a life cycle is taken as
the time when an organism first has an independent existance, e.g., at the
division point of cell(s).
				Bill Tivol

More information about the Bioforum mailing list