Íslenskar landbúnaðarrannsóknir - 01.03.1970, Side 47

COLOUR INHERITANCE IN ICELANDIC SHEEP 45
B^B^S^S^. He was lightgrey and was
bought in on basis of the colour in the
belief that he would be homozygous grey.
He was well tested with respect to genes
for both pigment and white markings. He
gave altogether 26 nonwhite progeny out
of other ewes in this year, and they all
showed the A2-ailele.
The dam, No. 10004, genotype A4A.-B2
BoS^So, born in 1955, was not on record
until 1958/59. In that year and the year
after she was mated to sire No. 10008, geno-
type A^Ag— B2-----, and gave 1 white, 1
brown mouflon and 1 brown lamb.
Two lieterozygous white sires, No. 10008
above and 10007, genotype A^AgB^ — S^—,
were used on the farm in 1960/61,, and
both could have given this colour of pro-
geny with ewe No. 10004.
Case 7. Mating A2A4 X A2A5.
One black larnb.
The lamb was born on farm No. 5. Date
of mating 8/1/1961, date of lambing un-
known. One lamb, a black female.
The sire, No. 05049, genotype A2A4Bj
B^S^—, produced another black lamb in
the same year when mated to another grey
ewe of genotype A2— B4— S4— . The dam
of the first lamb was ewe No. 05606, geno-
type A^AjjB^BgS^—, and the dam of the
second ewe No. 05555. They are unrelated
as far as can be seen.
Another sire on the farm, No. 05051,
genotype A^AgB^B^S^—, sired several
black lambs tliis year, and so did sire No.
05026, genotype A4 A5Bj B^S^S^. Faulty
parentage can therefore not be excluded.
Under the assumption that the records are
correct, either the A2-allele or the A4-allele
has mutated to A5.
Case 8. Mating A2A5 X A2A3.
One grey mouflon lamb.
The lamb was born on farm No. 7. Date
of mating 20/12/1960, date of lambing
14/5/1961. Twins, a darkgrey male and a
grey mouflon female. Enquiries about the
lamb indicated tliat an error has been
made in writing down the colour of the
lamb in the flock book. The lamb was
most likely black badgerface which would
have been expected from this mating.
Case 9. Mating A2A5 X A5A3.
Two white lambs.
The lambs were both born on farm
No. 8.
The first lamb was from a mating of
unknown date with date of lambing 17/6/
1958. One lamb, a white male. The dam
was No. 08038, brown, genotype A5A5B2
B2S4— . the sarne as reported in case 5.
The sire was No. 08017, grey, genotype
A2A5B4 b2s4— .
The ewe had first been mated to sire
No. 08015 on 31/12/1957 but had not con-
ceived. The nrating at which she conceiv-
ed has taken place around 24/1/1958 if
one assumes the gestation length to have
been 144 days. This is after the end of the
normal breeding season. Mating to two
different rams on two consecutive days in
order to ensure conception cannot be rul-
ed out, particularly because the ewe had
been barren the previous year. It is on the
other hand unlikely that the sarne would
apply to the anomalous result described in
case 5 for the same ewe.
It is unlikely that the ewe carried a
dominant gene whicli suppressed ordinary
white colour, because both her parents
were white. It is also very unlikely that
she carried the A2-allele without mani-
festation, cf. case 5, as both her parents
were of genotype A4A5 and botli showed
this genotype on several occasions in other
progeny than ewe No. 08038.
The second white lamb out of an