Íslenskar landbúnaðarrannsóknir - 01.03.1970, Síða 52

50 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
TABLE 11
Progeny of ram No. 06043, an nnusual type of lightgrey
Genotype of ewes Colours of progeny Total
01 02 03 04 05 11 12
Ai- 3 3
AiA2 1 1 9
AiA4 1 1
AiA5 3 4 4 11
a2a2 1 1 2 4
A2A3 1 1 2
A0A5 1 3 1 4 3 12
A3A5 1 1 1 3
A4A5 2 10 5 17
A5A5 4 13 25 42
Total 16 5 1 29 40 5 1 97
genotype and the A4A4-ewe. No informa-
tion can be obtained from the lambs of
these ewes about the ram’s genotype. In
the second group are ewes heterozygous for
Ax which don’t carry A4, in the third
group A4A5-ewes, and in group 4 ewes
which carry neither A4 nor A4. The result
of this grouping is set out in table 12,
where the lambs are classified into 3
groups, 1, 2 and 3, according to whether
they show allele A1; A4 or absence ot' both,
respectively.
Several different hypotheses about the
ram’s genotype can now be tested on basis
of the results in table 12.
One might eventually suspect that the
ram was heterozygous for a dominant gene
which partially suppressed white, and that
he also was heterozygous for the A^-allele.
Then one woukl expect 25 per cent of his
progeny out of nonwhite ewes to be white,
i.e. 16 white and 64 nonwhite lambs would
be expected among the 80 lambs out of
ewe groups 3 and 4. d'he observed numb-
ers of 8 white and 72 nonwhite differ
significantly from a 1:3 ratio (x24 = 5.000;
P < 0.05). This hypothesis must therefore
be rejected.
The possibility that the sire was of geno-
type A4A5, and that the white lambs were
of a recessive type, can be tested on the
lambs out of ewe group 4, under the as-
supmtion that the recessive white would be
expressed independentlv of whether the A4-
or Ag-allele from the sire was present.
Under this assumption one would expect
progeny obtaining A4- and A5-allele from
the sire in the ratio 1:1. The observed
numbers, 21 lambs obtaining allele A4 and
36 obtaining allele A5 from the sire, differ
significantly from a 1:1 ratio (x24 = 3.947;
P < 0.05). The white lambs can therefore
not be explained by assuming them to be
recessive white.
The hypothesis that the sire carried a
new type of dominant white, not allelic to
A4 or Ag could be tested by the same
criterion as the test for recessive white, be-