12
d*=o D'=2 D"=6
COMB PHENOTYPE
COMB SIZE PHENOTYPE SMALL
t
"T LARGE
Duplex
Hutt FB and Lamoreux WF, 1940. Genetics of the fowl: 11. A linkage map for six chromosomes. J Hered 31: 231-235. Hutt FB and Mueller CD, 1943. The linkage of polydactyly with multiple spurs and duplex comb in the fowl. Am Nat 77:70-78. May CG (ed), 1971. British Poultry Standards. Boston: Newnes-Butterworths. Punnett RC, 1923. Heredity in poultry. London: Macmillan; 94-98. Somes RG Jr, 1986. Multiple alleles at the duplex comb locus of the domestic chicken. Poultry Sci 65(Suppl 1)129
Normal d*d*
cT
D"D° Dvd* GENOTYPE
D'D°
DVDV
Figure 2. A proposed threshold effect involving the D-locus alleles and the comb types and size phenotypes.
Some Observations on High Cavernous Nostrils in the Chicken R. G. Somes, Jr.
The data presented here show that these two comb types react quite differently when crossed onto the same genetic backgrounds and would strongly suggest that two separate alleles are involved. It is proposed that an allele semi-dominant to the nonduplex allele (), it is evident that Dv is dominant to IX; thus, the order of dominance is Dv > & > d*. Also the added strength of the & allele, which in itself does not suppress comb size, when added to that of the Dv allele does allow for a single Dv allele to suppress comb size. These allelic actions are presented graphically in Figure 2 where two thresholds of expression are proposed. One determines the ability of these alleles to cause dou-
1 7 2 The Journal of Heredity 1991:82(2)
bling of the comb, while the other influences the overall size of the comb. With hypothetical values attached to the individual alleles and considering an additive influence from each as they combine in the gametes, a gametic value of two to six allows for a large duplex comb, while values of eight or more produce a duplex comb smaller in size. These data help explain how such varied phenotypic expressions as the buttercup and horn V-shaped combs can: be controlled by the same locus. The leaf V-shaped comb was not studied here, but it may well be controlled by yet another allele at this locus with intermediate dominance between EX and Dv. From the Department of Nutritional Sciences, University of Connecticut, Storrs. This is Scientific Contribution No. 1331 of the Storrs Agricultural Experiment Station. Address reprint requests to Dr. Somes, Department of Nutritional Sciences, Box U-17, Room 109, 3624 Horsebarn Rd. Ext., University of Connecticut, Storrs, CT 06269-4017.
References American Poultry Association, Inc., 1983. The American Standard of Perfection. Troy, NY: American Poultry Association, Inc. Bateson W and Punnett RC, 1905. Experimental studies in the physiology of heredity. Poultry Repts Evol Comm Roy Soc 11:99-119. Bateson Wand Punnett RC, 1908. Experimental studies in the physiology of heredity. Poultry Repts Evol Comm Roy Soc IV:18-35. Davenport CB, 1906. Inheritance in poultry. Carnegie Inst Washington Publ 52:1-136. Hurst CC, 1905. Experiments with poultry. Repts Evol Comm Roy Soc 11:131-154. Hutt FB, 1941. Genetics of the fowl: 15. Multiple spurs, a mutation linked with duplex comb. J Hered 32:356364. Hutt FB, 1949. Genetics of the fowl. New York: McGrawHill; 87-88.
Wide high cavernous nostrils are characteristic of all chicken breeds of the V-shaped duplex comb type, whereas all other breeds have slit-type nostrils, including the Sicilian Buttercup breed that has the buttercup-type duplex comb. Crosses between the Sicilian Buttercup and La Fleche breeds and single comb breeds suggest that this trait is a pleiotropic effect of the Dv allele at the duplex locus and is inherited as a recessive when crosses are made to the wild type (d*). The buttercup allele (/>) at this same locus does not influence nostril morphology by itself, but, when combined with the V-shape comb allele (DVIDP), it does allow a single Dv allele to produce mutant nostrils. In this case the inheritance appears dominant. It is proposed that cavernous nostrils are a pleiotropic effect of the comb-size-reducing ability of the Dv allele rather than its duplexing ability.
High or wide cavernous nostrils are characteristic of such domestic fowl ( Gallus domesticus) breeds as the Crevecoeur, La Fleche, Breda, Polish, Sultan, and Houdan. In the American Standard of Perfection (American Poultry Assoc. 1983), all of these breeds are also described as possessing the horn V-shaped duplex comb, whereas the British Poultry Standards (May 1971) distinguishes the Houdan breed from the other as having a leaf V-shaped duplex comb. The British Poultry Standards (May 1971) also describe the Houdan as having "wide nostrils," whereas the nostrils of the other breeds with horn V-shaped combs are described as "being large and rising above the curve line of the beak." Another duplex comb breed, the Sicilian Buttercup, has normal slit-type nostrils and its duplex
Downloaded from https://academic.oup.com/jhered/article-abstract/82/2/172/826960 by INSEAD user on 18 December 2018
t ""I""
tween the single comb breeds and both the La Fleche and the Sicilian Buttercup breeds, as well as the F, cross between these two duplex comb breeds. Results and Discussion
comb is of the extreme "buttercup" type. Duplex combs are governed by an autosomal locus containing three alleles with the order of dominance being Dv > D° >
d*=o D'=2 D"=6
COMB PHENOTYPE
COMB SIZE PHENOTYPE SMALL
t
"T LARGE
Duplex
Hutt FB and Lamoreux WF, 1940. Genetics of the fowl: 11. A linkage map for six chromosomes. J Hered 31: 231-235. Hutt FB and Mueller CD, 1943. The linkage of polydactyly with multiple spurs and duplex comb in the fowl. Am Nat 77:70-78. May CG (ed), 1971. British Poultry Standards. Boston: Newnes-Butterworths. Punnett RC, 1923. Heredity in poultry. London: Macmillan; 94-98. Somes RG Jr, 1986. Multiple alleles at the duplex comb locus of the domestic chicken. Poultry Sci 65(Suppl 1)129
Normal d*d*
cT
D"D° Dvd* GENOTYPE
D'D°
DVDV
Figure 2. A proposed threshold effect involving the D-locus alleles and the comb types and size phenotypes.
Some Observations on High Cavernous Nostrils in the Chicken R. G. Somes, Jr.
The data presented here show that these two comb types react quite differently when crossed onto the same genetic backgrounds and would strongly suggest that two separate alleles are involved. It is proposed that an allele semi-dominant to the nonduplex allele (), it is evident that Dv is dominant to IX; thus, the order of dominance is Dv > & > d*. Also the added strength of the & allele, which in itself does not suppress comb size, when added to that of the Dv allele does allow for a single Dv allele to suppress comb size. These allelic actions are presented graphically in Figure 2 where two thresholds of expression are proposed. One determines the ability of these alleles to cause dou-
1 7 2 The Journal of Heredity 1991:82(2)
bling of the comb, while the other influences the overall size of the comb. With hypothetical values attached to the individual alleles and considering an additive influence from each as they combine in the gametes, a gametic value of two to six allows for a large duplex comb, while values of eight or more produce a duplex comb smaller in size. These data help explain how such varied phenotypic expressions as the buttercup and horn V-shaped combs can: be controlled by the same locus. The leaf V-shaped comb was not studied here, but it may well be controlled by yet another allele at this locus with intermediate dominance between EX and Dv. From the Department of Nutritional Sciences, University of Connecticut, Storrs. This is Scientific Contribution No. 1331 of the Storrs Agricultural Experiment Station. Address reprint requests to Dr. Somes, Department of Nutritional Sciences, Box U-17, Room 109, 3624 Horsebarn Rd. Ext., University of Connecticut, Storrs, CT 06269-4017.
References American Poultry Association, Inc., 1983. The American Standard of Perfection. Troy, NY: American Poultry Association, Inc. Bateson W and Punnett RC, 1905. Experimental studies in the physiology of heredity. Poultry Repts Evol Comm Roy Soc 11:99-119. Bateson Wand Punnett RC, 1908. Experimental studies in the physiology of heredity. Poultry Repts Evol Comm Roy Soc IV:18-35. Davenport CB, 1906. Inheritance in poultry. Carnegie Inst Washington Publ 52:1-136. Hurst CC, 1905. Experiments with poultry. Repts Evol Comm Roy Soc 11:131-154. Hutt FB, 1941. Genetics of the fowl: 15. Multiple spurs, a mutation linked with duplex comb. J Hered 32:356364. Hutt FB, 1949. Genetics of the fowl. New York: McGrawHill; 87-88.
Wide high cavernous nostrils are characteristic of all chicken breeds of the V-shaped duplex comb type, whereas all other breeds have slit-type nostrils, including the Sicilian Buttercup breed that has the buttercup-type duplex comb. Crosses between the Sicilian Buttercup and La Fleche breeds and single comb breeds suggest that this trait is a pleiotropic effect of the Dv allele at the duplex locus and is inherited as a recessive when crosses are made to the wild type (d*). The buttercup allele (/>) at this same locus does not influence nostril morphology by itself, but, when combined with the V-shape comb allele (DVIDP), it does allow a single Dv allele to produce mutant nostrils. In this case the inheritance appears dominant. It is proposed that cavernous nostrils are a pleiotropic effect of the comb-size-reducing ability of the Dv allele rather than its duplexing ability.
High or wide cavernous nostrils are characteristic of such domestic fowl ( Gallus domesticus) breeds as the Crevecoeur, La Fleche, Breda, Polish, Sultan, and Houdan. In the American Standard of Perfection (American Poultry Assoc. 1983), all of these breeds are also described as possessing the horn V-shaped duplex comb, whereas the British Poultry Standards (May 1971) distinguishes the Houdan breed from the other as having a leaf V-shaped duplex comb. The British Poultry Standards (May 1971) also describe the Houdan as having "wide nostrils," whereas the nostrils of the other breeds with horn V-shaped combs are described as "being large and rising above the curve line of the beak." Another duplex comb breed, the Sicilian Buttercup, has normal slit-type nostrils and its duplex
Downloaded from https://academic.oup.com/jhered/article-abstract/82/2/172/826960 by INSEAD user on 18 December 2018
t ""I""
tween the single comb breeds and both the La Fleche and the Sicilian Buttercup breeds, as well as the F, cross between these two duplex comb breeds. Results and Discussion
comb is of the extreme "buttercup" type. Duplex combs are governed by an autosomal locus containing three alleles with the order of dominance being Dv > D° >
