Published online by Cambridge University Press: 14 April 2009
(1) In heterozygous condition, the gene for Patch (symbol Ph) produces spotting with sharply defined pigmented and white areas. The extent of the spotting is under the control of the genetic background.
(2) The Ph/Ph homozygote is inviable and dies before birth. In 9-day embryos, clear liquid is found flanking the notochord; in addition, there may be excessive amounts of liquid in the pericardium, the circulation, the tissues, and under the epidermis. The more extremely affected Ph/Ph embryos die at about 10 days. About one-third survive to later stages of pregnancy. Such ‘cleft-face’ embryos have a large bleb of liquid in the middle of the face which interferes mechanically with the formative movements of the nose and palate, and many subepidermal blebs elsewhere.
(3) Ph is closely linked to the gene for dominant spotting with macrocytic anaemia (W, Wv) in linkage group III, the crossover percentage being 0·077. There is a striking interaction in the double heterozygote Ph + / + Wv which is almost white, but nearly equally striking interactions occur with other spotting genes (s, bt and Miwh).
(4) By itself, Ph has no detectable effect on the coat colour, but in the double heterozygote with Wv, it slightly increases the dilution effect of the latter in the regions which remain pigmented. Similarly, Ph by itself has no appreciable effect on the red-blood picture of 13–14-day-old animals, but in the double heterozygote with Wv, it probably slightly increases the mild macrocytic anaemia produced by that gene. It remains unknown whether the Ph/Ph homozygote has an effect on the blood. Unlike W/W and Wv/Wv, Ph/Ph has no appreciable effect on the primordial germ cells.
(5) The relationship between Ph and the W-series is discussed.