Íslenskar landbúnaðarrannsóknir - 01.03.1970, Síða 46

44 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
white markings could not be found direct-
ly, and no definite proof can be provided
to show that he carried these genes. One
of his sons, however, No. 01540, of geno-
type A^AoBjB^------, was out ol' a grey
ewe which had a probability of 0.72 of
being homozygous for black pigment. This
son had therefore probably obtained the
B2-allele from his sire, No. 01509. White
markings were common among nonwhite
sheep in tlie flock where sire 01509 was
purchased.
If this case is to be regarded as a muta-
tion of Ax to Ag, the A^-allele cannot be
regarded as a deletion, as this would pre-
vent a back mutation to A5.
Case 2. Mating AjA3 X A5A5.
Three grey lambs.
This case has alredy been discussed ear-
lier, p. 30.
Case 3. Mating AXAS X A^A^.
One black lamb.
The lamb was born on farm No. 7. Date
of mating 2/1/1961. Date of lambing 26/5/
1961. Two lambs, white male and black
male.
The sire, No. 07035, genotype A^Ag— B2
Sx—, was well testecl and gave no progeny
with unexpected colour except this one.
The dam, No. 07016, genotype A]A4—
------, was also well testecl. In matings
prior to 1961 she produced one black mou-
flon lamb when mated to a black sire, 4
white and 2 black mouflon lambs when
mated to AjAg-sires, ancl 4 white lambs
when mated to homozygous white sires.
This is a case where mismothering could
very well have occurred, as altogether 5
rams used on the farm in this year could
sire black lambs. Any other conclusion
would therefore be of doubtful value.
Case 4. Mating A4A5 X AxAg.
One grey lamb.
The lamb was born on farm No. 13.
Date of mating 12/12/1959, date of lamb-
ing unknown. Twins, white íemale and
grey female.
The sire, No. 13082, genotype A^AgBj
---S2, was well tested and this was the
only exception arnong his progeny.
The dam, No. 13526, genotype A^Ag—
-----, hacl previously given 3 white
lambs by mating to white sires of geno-
type At—, and one white and one black
lamb wlien matecl to a sire of genotype
A3Ag—Bo------. When mated to sire No.
13082 again in 1961 she produced 2 white
lambs.
No definite sire on the farm in 1959/60
was known to carry A2, but as the records
from this farrn are not complete the case
will be left open to doubt.
Case 5. Mating A4A5 X AgAg.
One grey lamb.
The lamb was born on farm No. 8. Date
of mating 6/1/1960. Date of lambing 31/5/
1960. One lamb, a grey male.
The sire, No. 08015, genotype A^AgB^
— Sx—, was well tested, and this was the
only exception arnong this progeny.
The dam was No. 08038, brown, geno-
type AgAgBoBoS^- .
The lamb could have been the progeny
of a grey sire used on the farm in the same
year.
The ewe gave progeny of unexpected
colours in another year, see case 9.
Case 6. Mating A2A2 X A4A5.
White and black mouflon
twin pair.
The lambs were born on farm No. 10.
Date of mating 31/12/1960, date of lamb-
ing unknown. Twins, a white male and a
black mouflon female.
The sire was No. 10010, genotype A2A2