Íslenskar landbúnaðarrannsóknir - 01.03.1970, Blaðsíða 50

48 ÍSLENZKAR LANDBUNAÐARRANNSÓKNIR
TABLE 10
Colour of progeny of ram No. 01055
Genotype of ewes Colour code of progeny Total
01 02 03 05 06 09
A1A2 1 1
A1A3 1 1 2
A1A5 2 1* 2 5
a2a5 3 4 2 1 10
A3A5 2 1* 3
a5a5 2 2
Total 4 3 3 6 4 3 23
Unexpected colours.
scribed as brown wlien he was purchased
in autumn 1956. When he was slaughtered
in autumn 1957, at 18 months of age, it
was discovered by chance, on inspection of
the pelt, that he had a large patch of grey-
brown colour on the right hind leg, ex-
tending forward towards the middle of the
right side. This jratch had not been dis-
covered before, presumably because the
ram had a long and dense outercoat and
the greybrown patch was visible only by
parting the fleece.
This greybrown patch and the two grey-
brown lambs jrroduced by the ram indicate
that the ram was a mosaic with respect to
to colour, the mosaicism being visible in
the greybrown patch and also present in
the gonads.
The colours of the progeny of the ram
are shown in table 10.
The table shows that among the 19 non-
white progeny the 3 grey and 2 greybrown
lambs in the 4th line conlcl all have ob-
tained their A2-allele from their dams'. If
this is assumed to be^söf thé rahtTias given
the A2-aliele to 2 nonwhité prögény öut
of 19. This again indicates that a nruta-
tion of Ag to A2 has taken jrlace at the
4-cell stage of the embryo, i.e. that the
ratio between A2- og A5- alleles was 1:7.
The probability that the sire was in
reality greybrown of genotyjie A2A5B2B2
is very low, because then one would
have exjDected about half of his jarogeny
to have obtained the A2-alleie frorn him.
Under the assumption that none of the
grey and greybrown lambs in the 4th line
of table 10 obtained the A2-allele from
their sire, the observed ratio of 2:17 differs
highly signficantly from the 1:1 expecta-
tion (x2! = 8.895;" P<0.01).
2. Discussion of unexpected colours
The cases of unexpected colours describ-
ed above can in several instances be ascrib-
ed to faulty records of the parentage of
the lambs.
In cases 13 and 16, faulty parentage is
excluded, ancl the only explanation there
seems to be a mutation of allele A5 to
A2. In case 1, the brown lamb with white