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171   Human Mutation Can Scramble the Coded Genetic Message of DNA
      The Washington Post   October 4, 1969

     In the normal cycle of generations, every individual receives
his endowment of genetic information in equal portions of DNA from his
two parents.  Each portion of DNA is represented by a set of 23
chromosomes, allotted at random from the 23 pairs of the parent in the
formation of an egg or a sperm.  For better or worse, the DNA message
is a faithful copy of what was inherent in the parent, except for the
mishaps that we call genetic mutations.

     Many environmental factors are either known to add to our burden
from mutational mishaps, as in the case of radiation, or suspected of
doing so, as in the case of many chemicals.  It is important that
the complexities of such insults be carefully examined and more widely
understood, and to do this demands an orderly classification of a wide
range of events and their consequences.

     The kind of cell in which a mutation occurs is all-important.
Every cell of the body is programmed by a copy of the individual's
DNA and is subject to mutation. Only if the cell in question is a germ
cell, leading to an egg or sperm, is there a possibility of
transmitting the mutation to the offspring.  And then it will have no
effect on the person himself.

     Alternatively, mutations may occur in body cells, which can have
no effect on later generations.  Their effect on the person is
problematical; however, there is grave concern that some cancerlike
diseases such as leukemia stem from mutations in blood-forming
tissues.  In addition, the disorganization of an increasing proportion
of body cells by mutation is one of the plausible theories of aging.

     The main evidence for these concerns is that large doses of
radiation will induce leukemias and accelerate aging as well as
produce mutations in a proportion of all exposed cells.

     Germ-cell mutations are what we commonly think of as genetic
effects. (They must be distinguished from direct effects on the
growing fetus, such as those of thalidomide.  The deformations caused
by this drug involved only the limbs, and not the germ cells, and will
not be transmitted to further generations).

     Mutations are quite indiscriminately scattered over different
genes and chromosomes.  Up to the present time, we have not
encountered any chemicals or agents that can alter one variety of DNA
and leave other messages intact.  It is reasonable to predict that
some viruses will be found to act in this way, or that virus-like
molecules will be fabricated that might cause specific mutations --
perhaps even beneficial ones.  But we do not know this now.

     Mutations are classified along several lines.  The function or
organ affected may range from color vision to thought, from toenail
to scalp.  The severity of effect may be a cosmetic nicety like a
white forelock, a monstrosity incapable of surviving or, most tragic
of all, a physical deformity or mental handicap.  The mutation may be
dominant, immediately expressed in one generation, or recessive,
reshuffled through posterity until it appears simultaneously in a
uniting egg and sperm.

     In recent years, we have also become more aware of the
significance of chromosome mutations where a whole chromosome or a
large segment of one is imperfectly transmitted and mimics a dominant
mutation.

     Except for dominant mutations, we have little direct evidence of
new occurrences of these various events in man.  We live under a
substantial burden of a historic legacy: the simplest way to describe
the genetic load is to say that a third of fertilized eggs fail to
complete a normal life cycle.  Fortunately, most of these events are
manifest as spontaneous abortions;  but all too much misery already
spills over into the lives of born children and their families.
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