Íslenskar landbúnaðarrannsóknir - 01.03.1970, Qupperneq 52

Íslenskar landbúnaðarrannsóknir - 01.03.1970, Qupperneq 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-
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