Íslenskar landbúnaðarrannsóknir - 01.03.1970, Blaðsíða 30

28 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
were found to be segregating for the alleles
Ao and A4, while one died and 2 were
sold before they could be tested. All the
grey mouflon rams used in Skeidháholt
also segregated for the alleles A2 and A4,
and all the grey badgerface animals were
found to segregate for the A2- and A;J-
alleles.
In all other respects the observed colours
of the lambs in this flock were consistent
with the conclusions drawn from the earli-
er experiments.
In autumn 1960 a lightgrey ram lamb
bred from white parents was purchased
and tested on a private farrn, No. 17. 'I'liis
ram came from a flock in Eastern Iceland
where grey colour was predominant among
nonwhite lambs from white parents.
It was obvious that if the pattern genes
were allelic to the gene for white, all grey
progeny fronr white parents heterozygous
for grey would be homozygous grey, and
from the residts in the Skeidháholt flock
it could be assumed that homozygous grey
animals would often be lightgrey.
This ram was mated to black ewes the
next winter, and of the lambs born in
1961, 25 were darkgrey ancl 8 darkgrey-
brown, while neither lightgrey nor black
or brown progeny were born.
The ram was therefore homozygous for
the gene for grey, but heterozygous with
respect to pigment genes, i.e. of genotype
A^AoB^B^. This experiment also showed
that the heterozygous grey progeny were of
a much darker colour than their sire.
The grey mouflon ram mentioned ear-
lier (p. 27) bred from a black ram and a
grey mouflon ewe, was tested on a neigh-
bouring farm, farm No. 18, in the same
year by mating him to black ewes. The
result was 8 grey mouflon and 8 black
progeny, and neither grey nor black mou-
flon progeny were produced. This is the
only ranr of the genotype A6A5 that was
tested in the present study.
C. WHITE COLOUR AND THE
PATTERN GENES
In 1960 it was decided to test the rela-
tionship between the pattern genes and
the genes for white further. It was also
found to be of considerable interest to in-
vestigate the occurrence of hypostatic co-
lour genes in homozygous white sheep.
At this stage of the experimentation all
the records for the ewes in the experi-
mental flock at Hestur had been inspect-
ed and all ewes had been genotyped with
respect to colour as far as was possible.
During this inspection a few white ewes
in the flock were found to carry the gene
for grey, and these ewes were of interest
in connection with production of homo-
zygous grey animals. At the same time
several white ewes were found which had
been tested fairly well with respect to the
occurrence of genes for nonwhite colour,
without ever having given nonwhite lambs.
Two ram lambs were selected for these
experiments in autumn 1960. One of thenr,
No. 01091, was grey badgerface. It was de-
cided to use this ram on some of the white
ewes carrying genes for grey and also on
2 grey badgerface ewes, in order to pro-
duce homozygous grey animals. This ram
was also mated to white ewes which had
earlier given black lambs and also to black
ewes in order to test further the segrega-
tion of the genes for grey and badgerface.
He was also mated to some white ewes
which had never given nonwhite progeny
before. Some of these ewes had a high
probability of being homozygous white
while others were less well tested. From
the last matings it was intended to obtain
white ram lambs for further experiments
in the next year.
The other ram kept for the experiments
in 1960, No. 01097, was a greybrown mou-
flon, son of ram No. 01079 and a grey-
brown ewe.