Íslenskar landbúnaðarrannsóknir - 01.03.1970, Page 67

COLOUR IXUERITANCE IN ICELANDIC SHEEP 65
TABLE 25
Progeny of heterozygous grey rams during and after test-year, when mated to
ewes of known genotypes. White progeny from A^A^-ewes not included
Genotype of dam Test-year Later years Both sets X2l Hetero- geneity X2i
Progeny showing allele
A2 A5 Total X2i A2 a5 Total X2i
AoA5 (a) 15 16 31 11.710** 42 21 63 2.333 10.340** 3.703
AjAg (b) 8 15 23 2.130 16 17 33 0.030 1.143 1.017
A3A5 (c) 7 11 18 0.889 7 12 19 1.316 2.189 0.016
A5A5 (d) 27 28 55 0.018 49 72 121 4.372* 3.273 1.117
Sum (b, c, d) 42 54 96 3.0371) 72 101 173 5.7181) 6.6051)
X2l 1.500 4.861* 6.249* 0.112
Heterog. ^22 1.537 0.857 0.356
*) P < 0.05; **) PC0.01
1) DF = 3
ed reciprocal matings indicate that the
variation left is abnormally low, particul-
arly in line 6 of table 19. It is also notice-
able that this phenomenon is not rnani-
fested when the reciprocal matings are
kept separate. Tliis indicates an effect of
sex of parents on the segregation ratios
and a negative correlation between the
ratios from the reciprocal matings.
In table 26 are shown the x2’s for mat-
ings wliere n § 20 for both reciprocal
matings, first for the separate matings, then
for the reciprocal matings added and fin-
ally the heterogeneity between reciprocal
matings.
Table 26 shows that only one of the
heterogeneity ^2’s is significant, i.e. in the
AiA5 X A5A5-mating. In the added reci-
procal matings the A2A5 X A5A5-mating
shows a highly significant deviation from
expectation as mentioned earlier, while tlie
other addecl reciprocal matings show ^2-
values which are far below expectation
when added together (x25 = 0.5414; P>
0.99).
On examination of grouped matings
with respect to segregation ratios frorn add-
ed reciprocal matings with n > 20 the
picture given in table 27 emerges.
The grouping of matings shown in table
27 indicates strongly that matings involv-
ing the allele At sliow less variation in
segregation ratios than expected, while
matings where both parents are nonwliite
show greater variation.
The subnormal variation found in con-
nection with the A^-allele is in agreement
with results reported by Dry (1936), I.au-
vergne (1961) and Hayman and Cooper
(1964). Dry obtained 646 white and 213
black progeny wlien both parents were
known lieterozygous white (x2x = 0.0190;