Íslenskar landbúnaðarrannsóknir - 01.03.1970, Síða 118

116 ÍSLENZKAR LANDBUNAÐARRANNSÓKNIR
Allele Giving colour or pattern Dominant to Recessive to
Ai White All None
Ae Grey mouflon A2, A4, A5 Ai
A2 Grey a5 Ai, Ae
A3 Badgerface a5 Ai
A4 Mouflon a5 Ai, Ae
A5 No pattern None All
and S2, recessive, for presence of white
markings.
The results from planned breeding ex-
periments, which are described, confirm
the above hypothesis (Chapter III).
In addition to the results from the breed-
ing experiments extensive records from 24
sheep flocks were collected for analysis
(Chapter IV).
The segregation results with respect to
the alleles at the A-locus are given in Table
9 for 111 matings where both alleles of
both parents were known prior to the mat-
ing.
Colour description was available on 3452
iambs from these matings. Of these, 23
lambs or 0.67 per cent, showed colours
other than expected. These exceptions are
so few that the rnain hypothesis about the
allelic system at the A-locus is confirmed.
The unexpected cases are described in
detail. One case can be ascribed to muta-
tion of Ax to Ag. Another case can be
ascribed to mutation of Ag to A2 in a
brown ram, leading to colour mosaicism
and mosaicism in the gonads of the ram as
well. The other exceptions can be ascribed
to faulty parentage or faulty colour de-
scription.
A case is described where the two lambs
in a twin pair could be shown to have
been sired by two different sires.
A case of colour mosaicism in a pheno-
typically grey ram is described. Through a
breeding test the ram was shown to have
had the zygotic genotype A4A5. The allele
A4 is shown to have mutated to A4 at the
4-cell or 8-ceIl stage of the zygote (Chap. V).
A method was devised to estimate from
the data in table 9 the overall representa-
tion of the alleles A4, A2, A3 and A4, all
compared to allele A5. The estimation
showed that allele A2 was less frequently
represented among the progeny than ex-
pected. The deficiency was not significant
for each sex of parents separately, but signi-
ficant (P < 0.05) for sexes of parents com-
bined. The deficiency was confirmed in an
independent set of data.
Matings involving the allele A4 in both
parents showed subnormal variation in the
segregation ratios. (x23 = 0.2644; 0.99 > P
> 0.98). This was found for added reci-
procal matings with sexes of progeny and
singles and twins combined.
When 16,826 lambs with colour descript-
ion were grouped according to sex a signi-
ficantly liigher proportion of white lambs
was found among male than female lambs
(X21 = 7.196; 0.01 >P> 0.001). This sex
difference was similar for both singles and
twins. The proportion of white lambs was
also significantly higher among singles than
twins (x24 = 119.624; P< 0.001). No signi-
ficant difference in sex ratio could be de-
monstrated between colours among non-
white lambs.
A highly significant effect was found of