Abstract
1. A general description is given of the known effects of a series of allelic genes, W, Wv, w,, which are responsible for varying degrees of a macrocytic anemia as well as for differences in viability, gonad development and intensity and location of hair pigment. A summary is given of previous investigations into the basic nature of these anemias.
2. The mean erythrocyte count for each genotype is given for sixteen day embryos, and for zero day, two weeks and four weeks after birth. All determinations are based on comparisons of normal and anemic littermates.
3. A detailed description is given of the methods used to obtain blood samples from embryos. In all three severely affected genotypes the anemia is already well established at the sixteenth day of embryonic life.
4. In each interval thereafter, some increase in erythrocyte level is found in all genotypes. All genotypes, normal and anemic, made approximately the same relative increase during each time interval, indicating the same relative response to the physiologic stimulus of the individual’s growth.
5. Certain genotypes are lethal at particular stages. It is suggested that these deaths are due to a failure of blood formation to reach the absolute level necessary for continued development and resistance to minor noxious stimuli at these critical periods of rapid growth.
6. Certain other factors possibly affecting blood formation or survival were tested. The presence, absence or degree of anemia of the mother were found to have no effect on the erythrocyte level of newborn young of the slightly anemic Wvw genotype. Continuing injections of diluted whole blood into extremely anemic WWs led to survival for more than 100 days. Two WW individuals survived spontaneously to seven months, indicating that there are influences, as yet unanalyzed, which can lift even this genotype to a level where it can produce sufficient erythrocytes to maintain itself for a considerable period.
