Chapter 7

The Pigment Patterns of Allophenic Mice and Their Significance

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IV. Expression of Albinism and Occurrence of Bicolored Hairs

In considering the pigment patterns of allophenic mice it should be noted that Mintz's findings also are compatible with the fact that albino animals possess a population of amelanotic melanocytes since when allophenics are produced from merging an albino embryo with a pigmented one, the standard pattern is exactly like the one produced from two differently pigmented genotypes except that half the bands are white ( Figure 7-3). This as we will see, is quite different from the case when white-spotting is involved.

It is also important to mention that at interfaces between phenotypically different clones, and, to graded extents, toward the clonal interiors of allophenic mice not only does an intermingling of colors occur, but single hairs sometimes are populated with two colors. Thus in B/B <--> b/b allophenic animals both black and brown pigment granules occur within single hairs, and in Ln/Ln <--> ln/ln mice the septules of some hairs display clumped granules characteristic of leaden mice, whereas other regions of the same hairs possess a normal distribution of granules. These observations are important because they demonstrate that more than one melanoblast contributes toward the pigmentation of single hairs ( Mintz, 1967; Mintz and Silvers, 1970; Cattanach et al., 1972).

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