A comparative study of the coats of chimaeric mice and those of heterozygotes for <i>X</i>-linked genes

Abstract

SUMMARY The coats of Ta–Ta + and c–c + chimaeric mice have been compared with those of Ta heterozygotes and animals heterozygous for an X -autosome translocation which causes c -variegation. With one exception all those features typical of the heterozygotes were found in their chimaeric counterparts, thus showing that the creation of two cell populations by X -inactivation can ultimately lead to the observed heterozygous phenotypes. The one exceptional feature not found in c -variegated chimaeric mice was the progessive increase in the proportion of pigmented hairs in c areas with age which occurs in X -autosome translocation heterozygotes. The coat of a Mo dp / + – Ta chimaeric animal was also investigated. Ta hairs showing only the colour effect of Mo dp were numerous, suggesting that Mo dp and Ta affect different cell populations. However, Ta hairs showing the structural effect of Mo dp were very rare. The two observations suggest Mo dp can operate independently upon two different cell types – melanocytes and hair follicle cells.