(bleeder's disease) is where certain elements in the blood, which normally would stop a person from bleeding to death, are inadequate or missing. This means that his blood will not clot or thicken and harden at the site of a wound. from a simple cut. A person with this disease may die Diabetes is another disease with genetic origins. How mutation works was explained by Dr. James F. Crow, Professor of Genetics and Biology at the University of Wisconsin, before the U. S. Congressional hearings on fallout: "Let me answer Senator Bricker's question. "The implication of your question is that if I say the great majority of mutants that occur are harmful, why is it that the great majority of genes that now exist in the population are beneficial? "The reason for this is natural selection. The mutant genes that have occurred in the past have been weeded out by the process of natural selection so that the genes which now are part of the normal population are those which have been retained by this process of natural selection. Therefore, even though the great majority of mitants at the time they occur are such as to cause harmful effects to the descendants, the ones which cause the most harmful effects are eliminated by natural selection. The genes left in the population are the beneficial ones "A mutant that causes a great deal of harm is eliminated in a few generations. But one that causes only a small amount of harm will persist much longer, and thus affect a correspondingly larger number of persons. On the average the larger number affected by a mild mutation roughly compensates for the lesser effect on the individual “The total harm to the population, as measured by effects on future generations, is strictly proportional to the total amount of radiation received by the reproductive cells of the population." (94, p. 1012-3) This illustrates the basic difference between irradiation of normal somatic cells (like blood cells) and of the reproductive cells. Both can be dangerous; however, damage to somatic cells can be repaired -—- and at 1014631