Íslenskar landbúnaðarrannsóknir - 01.03.1970, Blaðsíða 111

COLOUR INHERITANCE IN ICELANDIC SHEEP 1 09
that the inheritance of grey seemed to be
complicated.
Morais et. al. concluded that their grey
colour (jardo) was recessive to uniform pig-
mentation, and that it was expressed with
both dominant and recessive pigmentation.
Berge (1958) concludes tliat grey gener-
ally is epistatic to black and brown and
that this gene turns black into grey and
brown into greybrown, but he also points
out the possibility that grey may show a
varying degree of dominance. In his later
work (1964 a) he points out that the vary-
ing conclusions reached by the various
authors may be due to different definitions
of the plienotype for grey. He also points
out that there may eventually exist several
types of grey. He states that animals which
are born grey or show greying at the base
of the staple within a month from birth
will, wlien interbred, give both grey and
black progeny. Animals which are born
completely black (not stated for how long
they will remain black) may develop so
many white fibres later in life that they
should be termed grey, but these animals
when interbred will only produce lambs
which are black at birth and remain black
for some time after birth. This type of
black is hypostatic to grey according to
Berge (1964 a).
Skárman (1961, 1963 a, b) concludes tliat
there seem to be several genes behind the
grey colour of the Gotland sheep.
There seems good reason to believe that
different criteria used for the classification
of animals as grey and non-grey account
for much of the discrepancies between
earlier results reported on the inheritance
of grey and the lack of agreement between
them and the results found in the present
study.
The possibility should also be borne in
mind, however, that grey colour could be
produced by genes at more than one locus.
It seems thus reasonable to assume that the
grey colour which is found in the grey
Karakul and other breeds which carry do-
minant black is different from the grey
colour which is rnost common among the
short-tailed North-European breeds. Do-
minant black suppresses both white colour
and the badgerface pattern completely
(Roberts, 1926) and would therefore be
assumed to suppress the action of the A2-
allele as well. Grey colour which manifests
itself in sheep carrying dominant black is
therefore most likely due to genes at a dif-
ferent locus from the A-locus.
F. WHITE MARKINGS IN NON-
WHITE SHEEP
The investigations concerned with the in-
heritance of white markings have been re-
viewed by Berge (1964 a).
Berge divides the white markings into
the following classes.
1. White blaze and head spot. This group
of markings is found in Russian north-
ern sliort-talied sheep in the Romanov
breed, in Olcl Norwegian and Ice-
landic sheep and eventually in non-
white Merinos Rambouillets (Ada-
metz, 1917; Vasin, 1928; Berge, 1958,
1964 a; Pálsson, 1944; Hayman and
Cooper, 1964).
2. White head spot and white tail. This
type of markings is found in Karakuls
and in many Russian breeds and also
in some British breeds and their cross-
es with the Piebald sheep. (Adametz,
1917; Roberts, 1926; Roberts and
White, 1930 b; Vasin, 1928).
3. Recessive piebaldness. This type of
markings is typical of the British Pie-
bald breed and is found when this
breed is crossed witli Dorset Horn
(Roberts, 1926). It is also conmion in
crosses between Merinos and breeds
with a black head and neck, and is