ABSTRACTS
69
Genes of interest in this study are : ' B, causing black hair, which is modified from
the solid color by the presence of the recessive gene s which causes white spotting of the
coat; bs, or lack of the factor for " blackish " hairs as found in the Brown Swiss and
Jerseys ; d, or lack of the dominant diluting factor which effects black ; I the normal
allele of the recessive dilution factor i; lack of the W factor which causes whitening in
the muzzle, coat, etc ; and In, or dominant white spotting in the inguinal region.' Some
Holsteins also have a dominant gene for the white star (Ws)
The F 1 data of this study show that the Brown Swiss carry ' bb, which would result
in red, except for the presence of Es (partially epistatic to red) and ii, the latter being
mostly effective on dilution of red ; D, which dilutes black to dun (one Brown Swiss male
was apparently heterozygous and the other homozygous for D) ; W,—(with one excep-
tion, the F 1 animals did not show the effects of the whitening gene because, probably,
black is epistatic to it) ; inin, or lack of all white spotting in the inguinal region— '.
This cross gives an issue which is complicated because of the presence of Bs. Brown
Swiss are self-coloured, S, and they may carry i.
One F 1 animal was reddish brown instead of black or dun as in the other F 1 W
was regarded, therefore, as dominant, instead of recessive as others have considered it,
and ' is hypostatic to black and would therefore appear as a recessive in the first cross
whenever black was involved in the cross. ' The dam of this animal must have been
heterozygous to black (B).
It was noticed from another F 1 animal that D may affect the black gene more than
the red and that i presumably affects the red pigment more than the black. The author
believes that i with its effects on red pigment is present in a homozygous condition in
gray animals. This condition was somewhat manifested in the back cross animals, i. e.
progeny of an F 1 female (Holstein-Friesian × Brown Swiss) and Brown Swiss male cross.
One back cross female was light in colour and two somewhat darker with large
amounts of red pigment ; all three had the white muzzle. Three back cross males were
dark ; one had the white muzzle, but two apparently carried black and did not show the
effects of W. One Holstein-Friesian must have been heterozygous for Ws as one of her
cross bred daughters had the white star and one did not.
Brown Swiss and Jersey seem to have the same colour genes except for s which is
found in some of the latter but the former lack it, the Jersey shows more red as well.
Holstein-Friesians probably do not carry Br, brindle, as none were recovered in the F 1
back crosses.
The colour genes in Brown Swiss are thought to be bb BsBs DD (or BsBs ? Dd) ii
WW inin SS brbr. W is considered dominant, whereas it was formerly thought to be
recessive. The dominant Ws is found in some Holstein-Friesians but this breed probably
does not carry Br.
[J. N. W. ]
'Nicking'in dairy cattle. D. M. SEATH AND J. L. LUSH (1940). J. Dairy
Sci. 23, 103.
'NICKING
' is a term sometimes used to mean that some mating or group of mat-
ings were unexpectedly good ; more rarely to mean unexpectedly bad. The sire and
dam may be said to have ' nicked well' or to have ' nicked poorly ', respectively.
Chance in Mendelian segregation may, however, cause an exceptional offspring in
spite of the fact that its most probable genotype will be midway between the genotypes
of the two parents. Several offspring from the same parents rarely deviate from the
expectation markedly in one direction as each gamete is an independent sample from the
genotype of the parent and sampling errors tend to cancel each other in the average.
The possibility of the genotype of one or both parents being far better, or worse,
than is supposed may give results termed ' nicking '. A genotype is known only imper-
fectly by the phenotype of the parent or progeny. This may be the cause of consistent
good results from the mating of a particular male and female. Errors in estimating geno-
types will, therefore, just as sampling errors in gene combinations in the individual mat¬
ing, tend to cancel each other in the case of a large number of parents.
Deviations in the effect of a given gene caused by other genes are known as epistatic
deviations, joint effects or non-additive combination effects. Certain combinations may