Íslenskar landbúnaðarrannsóknir - 01.03.1970, Page 99

COLOUR INHERITANCE IN ICELANDIC SHEEP 97
TABLE 57
Segregation at the S-locus from matings with genotypes of both parents known
Mating
White markings of progeny
Males
Females
Both sexes
Sire Dam Abs. Pres. Total Abs. Pres. Total Abs. Pres. Total
S1S2 X SiS2 3 0 3 5 0 5 8 0 8
SiS2 X S2S0 1 1 2 1 4 5 2 5 7
S2S2 X S1S2 27 29 56 29 24 53 56 . 53 109
S‘jSo X S2S2 0 88 88 1* 85 86 1* 173 174
Sum .... 31 118 149 36 113 149 67 231 298
*) Unexpected result
rings, to code number 80, white liead spot
only and code number 90, white socks only.
It should be pointed out that the 19 lambs
with no code number in the bottom of
table 58 had usually been described as pie-
bald (Icel.: flekkótt), without any further
definition.
Three types of white markings are of
considerable interest, as tliey have been
assumed to be inherited in a different way
from that found here. The first of these is
the hood (Persian liooded) which has been
assumed to be dominant and to give hood-
ed when liomozygous and piebald when
heterozygous, the second is the blaze which
has been assumed to be inherited as a
multifactorial character, and tlie third is
tlie white collar, which lias been reported
to be a dominant character (for references
see Berge, 1964 a).
The exact description of the white mark-
ings of the parents in the material was
limited, and as the number of parents with-
in any one class of white markings was
also very limited, a classification according
to code number of parents does not throw
much light on the exact nature of the in-
heritance of special types of white mark-
ings. One can, liowever, draw certain con-
clusions about the three types of wliite
markings mentioned above from the pre-
sent data. There were thus two rarns with
code number 44 used to a considerabe
extent, and several of the ewes they were
mated to were without white markings,
either known heterozygotes or with one un-
known allele at this locus. Code number
44 refers to a hood with some dark patches
and also a head spot or nose spot or both,
a type of markings which closely resembles
that found in hooded sheep of Asiatic
origin. The two rams mentioned above
should have given only piebald progeny
when mated to nonwliite ewes with white
markings, if the hood was dominant, but
instead they gave progeny with white mark-
ings only in those cases when the ewes
could be assumed to carry the S2-allele, and
they therefore gave altogether several pro-
geny without white markings. Tliis condi-
tion rnust therefore be regarded as reces-
sive in the Icelandic sheep.
With regard to the blaze markings which
have been assumed to have a mutifactorial