Genetics
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Major genes
These are: "all known mutations from ligands or recpeotrs of the transforming growth factor beta superfamily and point tot he bone morphogenic prtoein family of peptides as local regulators of ovarian follicular growth." (C. J. H. Souza, A. González-Bulnes, B. K. Campbell, A. S. McNeilly, and D. T. Baird. Mechanisms of action of the principal prolific genes and their application to sheep production. Reprod.Fertil.Dev. 16 (4):395-401, 2004.)
- Booroola (mutation in BMP receptor 1B; FecB)
- Inverdale (mutations in BMP15 gene; FecXH, FecXI)
- Thoka
- Javanese
- Olkuska
- Woodlands
- Lacaune
Specific inherited traits or defects
- Horns or scurs
(horn inheritance in Icelandic sheep)
- Face covering
- Color
- Skin folds
- "Silky" fleece condition
- Dwarfism
- Spider syndrome
- Jaw defects
- Rectal prolapse
- Entropion (inverted eyelids)
- Cryptorchidism
- Inherent blindness
Number of normal offspring of ewes producing normal offspring required to be 95 or 99% confident that a ram is not a carrier of a deleterious recessive gene:
Type of ewes |
Number of normal offspring or ewes to be 95% confident |
Number of normal offspring or ewes to be 99% confident |
Homozygous recessive (exhibit the trait) |
5 |
7 |
Known carrier (heterozygotes) |
11 |
16 |
Ewes with two known carrier parents |
17 |
26 |
Ewes with one known carrier parent |
23 |
35 |
Association between Melatonin Receptor 1A Gene Polymorphism and Reproductive Performance in Dorset Ewes (R. G. Mateescu, A. K. Lunsford, and M. L. Thonney. Association between Melatonin Receptor 1A Gene Polymorphism and Reproductive Performance in Dorset Ewes. J.Anim.Sci. 87:2485-2488, 2009
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Table 3. Effect estimates, SE and probability >| t| for contrasts evaluating the effect of season of birth or season of 1st conception and MnlI and RsaI genotype on the number of days from birth to 1st lambing and the number of days from the 1st to the 2nd lambing.
Contrast |
Days to 1st lambing |
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Days from 1st to 2nd lambing |
Days |
SE |
P>| t| |
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Days |
SE |
P>| t| |
| Effect of season of birtha or 1st conceptionb |
Early seasonal and late seasonal vs aseasonal |
-140.76 |
58.61 |
0.02 |
|
89.46 |
53.52 |
0.10 |
Early seasonal vs late seasonal |
30.7 |
77.86 |
0.70 |
|
-90.49 |
54.05 |
0.10 |
| Effect of MnlI genotype |
mm vs Mm and MM |
135.76 |
70.1 |
0.05 |
|
123.59 |
59.75 |
0.04 |
Mm vs MM |
-78.77 |
51.7 |
0.13 |
|
19.83 |
46.33 |
0.70 |
| Effect of RsaI genotype |
RR vs Rr and rr |
-2.20 |
54.25 |
0.97 |
|
-55.48 |
45.85 |
0.23 |
Rr vs rr |
-127.18 |
77.86 |
0.11 |
|
25.28 |
64.74 |
0.69 |
aSeason of birth was included in the statistical model analyzing days from birth to 1st lambing.
bSeason of 1st conception was included in the statistical model analyzing days from 1st to 2nd lambing. |
Inheritance of tail length in crossbred Finsheep (E. A. B. Oltenacu and W. J. Boylan. Inheritance of tail length in crossbred Finnsheep. J.Heredity 65:331-334, 1974.)
THE COVER: Two lengths of tail types in sheep are illustrated with the Targhee breed lamb (left) and the Finnsheep breed lamb (right) (see Inheritancde ot tail lenght in fcrossbred Finnsheep, page 331)
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Summary
Crossbreeding work with the short-tailed Finnsheep and the longer-tailed Minnesota 100, Suffolk, and Targhee breeds has shown this trait to be multigenic in nature, with some dominance for the short-tail genes. The heritability (using the sire component of variance) was found to be about 0.50 ± 0.24 in the standard breeds. No evidence for sex linkage was found, and sex influence appeared to be limited to that arising from differences in body weight. When Finnsheep were crossed with standard breeds, the progeny had markedly shorter tails than did the purebred standards. On the average, the tail lengths of Fl progeny were only about 67 percent as long as comparable parental standard- breed lambs. Enough variation existed in the crossbreds for selection for shorter tails to be considered in the development of new breeds based on initial crosses of Finnsheep with other breeds. The concept of ensuring that such new breeds would have not only the greater prolificacy of Finnsheep but also its short-tail characteristics has some economic importance in that it would preclude the necessity of docking lambs' tails.
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