COLOR INHERITANCE IN MAMMALS 



^ The Guinea-pig — Great Diversity in Coat-pattern, Due to Interaction of Many 



Factors in Development -Some Factors Hereditary, Others 



of the Nature of Accidents in Development 



Sewall Wright 

 Bureau of Animal Industry, Washington, D. C. 



' r~^lIE four scries of which dilution 

 I (Cd). black (Ab), yellow (Ey) 

 X and brown (b) are the recessivcs 

 have been shown to be inherited 

 independently of each other b}^ Castle' 

 who crossed wild Cavia cutler i of Peru 

 (CAEB) with a brown-eyed yellow race 

 of the tame guinea-pig, C. porcellus, 

 known not to transmit agouti 

 (C\iAbEyb). He obtained all of the 

 visibly distinct combinations in F2 in 

 proportions very close to those expected. 

 The pink eye factor (p) is known not 

 to be an allelomorph of any of the others 

 but thorough tests have not yet been 

 made for linkage. White spotting can 



AGOUTI -COLORED CAVIES 



Cavia culleri Bennett — SCAEBP. Cavia 

 porcellus Linn — SCAEBP. Cavia ritfes- 

 cens Lund— vSCArEBP i Patter us of black 

 and red or yellow) 



la, — 



s — picbiild 



2a 1 



2.12 



2a, 

 2b 



vS.s 



C. Cd, Cr, Ca 



A, Ar, Ab 

 1-:. Ep, Ey 



B,b 



P.P 



Cd — dilute (sepia and 

 yellow), Cr — red-eyed 

 dilute (sepia and 

 white), Ca — albino 

 Ar — ticked-bellicd 

 agouti, Ab — black 



Ep — tortoise, Ey — 



yellow 



b — b rown-eycd 

 brown agouti (brown 

 and red) 



p — pink eyed agouti 

 (pale brown and red) 



Classification explained in paper on the 

 mouse, JouR^fAL of Heredity, 8:373, 

 August, 1917. 



be combined with any color and so is no 

 doubt inherited independently. 



No dominant white is known in 

 guinea-pigs. A type of roan or silvering 

 is common but does not follow simple 

 Mendelian inheritance. A cross be- 

 tween a good roan and self produces 

 young which are usually slightly silvered 

 on the belly. Those in F2 are also 

 generally slightly silvered and there is 

 no clear-cut segregation. In these sil- 

 vered guinea-pigs there is not merely 

 an inteiTningling of colored and white 

 hairs but also an intermediate condition 

 within many hairs. Thus black, dull 

 black, and white hairs (or red, whitish 

 red and white) are found side b}- side. 



THE PIEBALD PATTERN 



Some grade of piebald between mere 

 traces of white to the black-eyed white 

 condition is almost universal among 

 tame guinea-pigs. The pattern is -ex- 

 ceedingly irregular and generally 

 asymmetrical. The writer has foimd it 

 exceedingly variable even within single 

 litters after sixteen generations of the 

 closest inbreeding and there can be no 

 (jucstion that a very large part of the 

 variability is not represented in the 

 germ-plasm. This is further demon- 

 strated by the low correlations (.15 to 

 .?){)) between parent and olTspring or 

 between brothers in stock bred at 

 random as regards pattern. The aver- 

 age quantit}' of white, nevertheless, 

 seems to be much more strongly inher- 

 ited than the pattern in which it is 

 disposed. The latter is inherited to 

 some extent, however, as MacCurdy 

 and (\istlc- were al)lc bv selection to 



» Castle, \V. E. 1916. Cam. Inst. Wash. Pub., No. 241, i)art 1, 55 pp. 



» MacCurdy, H. and Castle, W. E. 1907. Cam. Inst. Wash. Pub., No. 70, 50 pp. 



476 



