Two closely linked genes in the mouse

Abstract

(1) In heterozygous condition, the gene for Patch (symbolPh) produces spotting with sharply defined pigmented and white areas. The extent of the spotting is under the control of the genetic background.(2) ThePh/Phhomozygote 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 affectedPh/Phembryos 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)Phis closely linked to the gene for dominant spotting with macrocytic anaemia (W, W^v) in linkage group III, the crossover percentage being 0·077. There is a striking interaction in the double heterozygotePh+ / +W^vwhich is almost white, but nearly equally striking interactions occur with other spotting genes (s, btandMi^wh).(4) By itself,Phhas no detectable effect on the coat colour, but in the double heterozygote withW^v, it slightly increases the dilution effect of the latter in the regions which remain pigmented. Similarly,Phby itself has no appreciable effect on the red-blood picture of 13–14-day-old animals, but in the double heterozygote withW^v, it probably slightly increases the mild macrocytic anaemia produced by that gene. It remains unknown whether thePh/Phhomozygote has an effect on the blood. UnlikeW/WandW^v/W^v,Ph/Phhas no appreciable effect on the primordial germ cells.(5) The relationship betweenPhand theW-series is discussed.