Relative positions of the loci of the peacomb (P), eumelanin restrictor (Db), eumelanin extension (Ml) and plumage pattern (Pg) genes of the domestic fowl

A single comb Partridge Wyandotte bantam male was mated with two Indian Game bantam females to produce a double heterozygote of the linked eumelanin extension (Ml) and pea comb (P) genes. Four females so produced were mated with their sire to provide a backcross to the double recessive. Forty crossovers occurred among the 86 progeny suggesting linkage of approximately 46 units between Ml and P. The eumelanin restrictor gene (Db) had previously been shown to be linked with P, Ml and Pg by approximately 28, 10 and 17 units respectively and, furthermore, the locus of Ml had been shown to lie between the loci of Db and Pg. The locus of Db appears therefore to lie between the loci of P and Ml and hence the relative positions of the loci of the 4 genes is P, Db, Ml, Pg.     

Test for linkage between the eumelanin restrictor (Db) and the eumelanin extension (Ml) genes in the domestic fowl

A mating was made between a Gold-Pencilled Hamburgh bantam male and a double-laced bantam female to produce a double heterozygote of the linked eumelanin restrictor (Db) and eumelanin extension (Ml) genes. A male so produced was mated to a pen of Partridge Wyandotte bantam females, thus providing a backcross to the double recessive. Three crossovers occurred among the 31 female progeny suggesting linkage of approximately 10 units between Db and Ml. The pattern gene Pg has previously been shown to be linked with both Db and Ml by approximately 17 and 10 units respectively. The locus of Ml appears therefore to lie between the loci of Db and Pg.     

Inheritance of the black hackle of the Indian Game bantam.

1. An investigation was conducted among the progeny from crosses between pea-combed Indian Game and single combed double-laced Barnevelder bantams in an effort to determine the inheritance of the black hackle phenotype of the former. 2. The double-laced feather pattern phenotype of both breeds has been shown to depend upon homozygosity of both the linked eumelanin extension melanotic ML*M and the feather pattern arranging gene PG*P. However the hackles of the Indian Game are black, whilst those of the Barnevelder are partially striped, which suggests the presence of an extra eumelaniser in the genome of the Indian Game. This could not be due to variation at the extended black-E*-locus since the Indian Game and the Barnevelder have been shown respectively to depend upon the wheaten E*WH and brown E*B alleles; the former normally less heavily eumelanised. 3. A mating of a Barnevelder male with an Indian Game female produced 11 chicks, all of which were black in hackle. The mating of 2 F1 males with 5 Barnevelder females produced 35 chicks in the backcross to the double recessive, all of which were of parental phenotype. These comprised 18 peacomb, black in hackle and 17 single comb, partially striped hackle; classification being clear injuvenile plumage. 4. The absence of crossovers in the backcross suggest allelism or extremely close linkage between the loci of peacomb and the dominant eumelanin extension which causes the black in hackles. 5. The eumelanin extension isolated in this work appears therefore to be allelic to, if not a further manifestation of the well-established charcoal CHA*C gene.     

Hen-feathering mutation HF*H may act as a eumelanising factor and modify the expression of autosomal barring

1. An investigation was conducted amongst the progeny from a mating between a Hen-feathered Silver Spangled Hamburgh bantam male and a normal feathered Silver Fayoumi bantam female into the genotype of the plumage pattern of the latter. 2. Both breeds possess the marbled chickdown phenotype which has been shown to depend upon homozygosity of three genes: the birchen allele E*R at the extension locus, the dark brown Columbian-like eumelanin restrictor gene DB*B and the plumage pattern arranging gene PG*P. Furthermore, the Spangled Hamburgh was known to possess genes for Hen-feathering HF*H and for the melanotic ML*M eumelanin extension. The Fayoumi had been hypothesised to contain Columbian eumelanin restrictor genes CO*C. 3. The absence of lace-tailed laced segregants similar to the Sebright, of genotype homozygous HF*H, ER*R, CO*C, DB*B--ML*M--PG*P contradicts the hypothesis that the genome of the Fayoumi includes CO*C. 4. Comparisons of both Hen-feathered and normal feathered versions of the feather patterns discussed in this work demonstrated that the Hen-feathered version is more heavily eumelanised.     

Linkage mapping of the mouse nephrosis (nep) gene to chromosome 15.

ICGN is a partially inbred strain of mice with nephrotic syndrome caused by spontaneous glomerular lesion. It has been reported that the albuminuria in ICGN mouse was controlled by at least a single autosomal recessive gene (nep). In this study, we mapped the nep locus by linkage analysis of backcross progeny between ICGN and MSM mice using DNA pooling method. The linkage analysis revealed that the nep locus was localized on the distal part of chromosome 15.     

Inheritance of the laced plumage pattern of the blue Andalusian bantam

1. Crosses between Blue Andalusian and Gold-Laced Wyandotte bantams were made in an effort to determine the inheritance of the black-laced blue plumage pattern of the former. 2. The laced phenotype of the Gold-Laced Wyandotte had been shown to depend upon homozygosity of the linkage of a eumelanin intensifier, melanotic (Ml), with a pattern gene (Pg) in the presence of eumelanin restrictor, columbian (Co), and the brown (eb) allele at the E-locus; whilst the Blue Andalusian is homozygous for the extended black (E) allele at the E-locus and heterozygous for the eumelanin dilution, blue (Bl). 3. All patterned fowl in the F2 generation were laced, indicating an absence of segregation at the Co, Ml and Pg loci, and therefore that the genotype of the laced plumage pattern of the Blue Andalusian is E/E Bl/bl+ Co/Co (Ml-Pg)/(Ml-Pg).     

Evidence that the eumelanin restrictor genes (Co) and (Db) are present in the genome of the Buff Rock bantam

1. An investigation was conducted among the progeny from crosses between Buff Rock and Light Sussex bantams, and between Buff Rock and Gold‐Pencilled Hamburgh bantams in order to ascertain whether the eumelanin restrictor genes Columbian (Co) and Dark‐brown (Db) were present in the genome of the Buff Rock.

2. The Light Sussex and Gold‐Pencilled Hamburgh bantams used in this study were known to be Co/ Co db⁺ / db⁺ and co⁺ / co⁺ Db/ Db respectively.

3. In both F₂ generations the least eumelanin restricted segregants were as the parent mated with the Buff Rock, thus demonstrating the Buff Rock bantam tested to be Co/ Co Db/ Db, or possess similar alleles at these loci.

4. The Buff Rock bantam male was found to be heterozygous for a eumelanin inhibitor gene which appears to be dominant white (I).     

Further studies on the inheritance of the marbled chickdown phenotype of the domestic fowl.

1. An investigation was conducted among the progeny from crosses between Birchen Modern Game and Silver Sebright bantams into the inheritance of the marbled chickdown phenotype of the latter. 2. The marbled chickdown phenotype has been shown to depend upon homozygocity of both the birchen allele ER at the E-locus and the eumelanin restrictor gene Db. However, all stock used to establish this result were also homozygous for the linked eumelanin intensifier melanotic Ml and the pattern gene Pg, therefore yielding no information on the roles of Ml or Pg in the marbled chickdown phenotype. 3. Examination of the F2 generation both of chickdown and of adult plumage demonstrated the marbled chickdown to be homozygous ER (Db-Pg) with Ml dosage having an effect on adult plumage.     

Fine mapping of the region including hypogonadism (hgn) locus on rat chromosome 10

The hypogonadic rat (hgn/hgn) shows male sterility, reduced female fertility, and renal hypoplasia, controlled by a single recessive gene located on rat chromosome 10. We developed a fine map around the hgn locus using 565 rat backcross progeny and a Rat/Hamster radiation hybrid panel. The hgn locus was linked to Aldoc (aldolase c) and whn (winged helix of nude), and located in a 0.34-cM region between D10Rat30 and D10Rat68. The distance of the region was approximately 840-kb on rat physical map. Neither loci responsible for male sterility nor renal hypoplasia has been mapped on the homologous regions of mouse chromosome 11 and human chromosome 17. Identification of the gene responsible for the hgn mutation would provide important information on urogenital development.     

家鸡冠型与生产性能及冠型基因遗传规律的研究进展

冠型为家禽的品种特征之一,不同品种的鸡其冠形也有各自的特点和形状。家鸡冠型主要有单冠、豆冠、玫瑰冠、胡桃冠等4种类型,它们由2对基因控制,即玫瑰冠基因R和豆冠基因P,这2个基因位于不同的染色体上。现对冠型基因和生产性能关系,冠型基因的遗传规律及基因定位的研究作一概述。     

家蚕裸蛹基因(Nd)的SSR定位

家蚕裸蛹是自然突变产生的,裸蛹基因(Nd)与丝素重链基因(Fib-H)同处于第25染色体上,二者紧密连锁。利用家蚕雌性不交换的特点,以家蚕正常茧品种P50和裸蛹品种Nd为亲本获得P50×(P50×Nd)和(P50×Nd)×P50回交群体(分别记为BC1M和BC1F),再用已经构建的家蚕SSR分子标记连锁图谱对Nd基因进行定位,共筛选出7个与Nd基因连锁的SSR标记。BC1F群体中的所有裸蛹个体均表现出与(P50×Nd)F1相同的杂合型带型;而所有正常茧个体带型与亲本P50一致,为纯合型。利用另一个群体BC1M构建了Nd基因的遗传连锁图,连锁图的遗传距离为96.8 cM,Nd基因位于60.8 cM。同时得到了2个与Nd紧密连锁的SSR标记S2511及S2513,与Nd基因的距离分别为0.1 cM和1.1 cM。     

Genetic basis of the Melanotic Prat phenotype

1. The genetics of plumage colour of a melanotic columbian‐restricted male called ‘Melanotic Prat’ is described. It was found among the F₂ progeny of crosses between the Castellana and Prat breeds, and is very similar to the ‘quail’ phenotype.

2. Results of crosses involving this male indicate that its plumage colour pattern is the result of the Ml/Ml genotype adding black pigment to the Columbian plumage pattern produced by the e ^Wh and Co genes.

3. The melanotic gene (Ml) is recessive in the presence of the colum‐bian‐restricted genotype. It has no effect on the chick down colour although it could be a modifier to produce greyish or black back colourations when Co is present in the genotype.

4. It is suggested that the quail plumage colour is due to the same melanotic factor interacting with the primary pattern of a Columbian‐restricted genotype.     

Inheritance of the spangled plumage pattern and the marbled chick down phenotypes of the silver‐spangled Hamburgh Bantam

1. An investigation was conducted among the progeny from crosses between Silver‐Spangled and Gold‐Pencilled Hamburgh bantams, and between Silver‐Spangled Hamburgh and Double‐Laced Barnevelder bantams.

2. Two subjects were studied: the relationship between three plumage pattern phenotypes, spangling, transverse‐barring and double‐lacing, all of which are arrangements of eumelanin expressed on a background of phaeomelanic pigmentation and the inheritance of the marbled chick down of the Silver‐Spangled Hamburgh bantam.

3. Examination of the F₂ generations demonstrated that, in conjunction with silver (S) gene(s) and extended black (E) alleles at the E‐locus the silver‐spangled phenotype can be produced by the addition to the genotypes of the Gold‐Pencilled Hamburgh, homozygous e^bc (Db‐ml⁺‐Pg), and Double‐Laced Barnevelder, homozygous e^b (db⁺‐Ml‐Pg), of Sp and Db genes respectively. Consequently Sp and Ml are one and the same gene, for which I retain the symbol Ml, and the genotype of the Silver‐Spangled Hamburgh is homozygous E (Db‐Ml‐Pg), where the buttercup (e^bc) and brown (e^b) are alleles of the E‐locus and Db, Ml, Sp and Pg are respectively the eumelanin restrictor dark‐brown Columbian, the eumelanin extension melanotic, plumage pattern spangling and the pattern gene.

4. The exact correlation between S/‐ E/E Db/Db and the marbled chickdown phenotype demonstrated the latter to be a pleiotropic effect of Db/Db, thus enabling the mapping of Db, Ml and Pg in group 3 on chromosome 1.     

Inheritance of the plumage pattern of the double‐laced Barnevelder bantam

1. An investigation was conducted among the progeny from crosses between Gold‐Laced Wyandotte and Double‐Laced Barnevelder bantams into the genotype of the plumage pattern of the latter.

2. The double‐laced phenotype has been shown to depend upon homozygosity of the linkage of a eumelanin intensifier melanotic Ml with a pattern gene Pg in the presence of either wheaten e^Wh or brown e^b alleles at the E‐locus.

3. Examination of the female F₂ generation demonstrated that the plumage pattern phenotype of the Double‐Laced Barnevelder depended upon homozygosity of e^b(Ml‐Pg).     

Inheritance of the barred plumage pattern of the Silver Campine Fowl, together with its relationship to other patterned fowl.

1. An investigation was conducted among the progeny from a cross between a Silver Campine male and a Silver Spangled Hamburgh bantam female into the inheritance of the autosomal transverse barring of the Campine. 2. Both parental breeds possess the marble chickdown phenotype which has been shown to depend upon homozygosity of 3 genes; the birchen allele E*R at the E-locus, the eumelanin restrictor DB*B and the feather pattern arranging gene PG*P whilst the spangled feather pattern of the Silver Spangled Hamburgh has been attributed to homozygosity of E*R, DB*B, ML*M and PG*P, where ML*M is the eumelanin extension melanotic. 3. Examination in F1 and F2 generations of both chickdowns and adult plumage demonstrate that of the 4 loci, segregation occurs only for ML*M and hence the genotype of the Silver Campine to be homozygous E*R, DB*B, ML*N and PG*P. 4. The relationships between the genotypes of the Campine and those of other breeds with autosomal transversely barred plumage and between the Campine and those of other patterned fowl based on the E*R allele are discussed and presented in tabular form. In addition patterned fowl based on alleles other than E*R at the E-locus are included in order to demonstrate the effect of substituting E*R.     

Notes on the “wheaten” plumage phenotype of the domestic fowl

1. A study was made using a Light Sussex bantam hen to determine the allele present at the E locus. Conflicting results occurred on mating with different males suggesting the presence in one case of the dominant allele e^Wh and, in the other, of the recessive e^y.

2. Further examination of these apparently conflicting results suggests the possibility that there may be a single gene producing the wheaten phenotype which appears to be dominant if melanin restriction genes are present at other loci, or recessive by interaction with melanin intensifier genes. This gene may also require the presence of down‐diluting gene(s) to produce the wheaten phenotype.     

Evidence that the mottled (mo) and pied (pi) plumage genes of the domestic fowl are identical

1. An investigation was conducted among the progeny from crosses between Exchequer Leghorn and Ancona bantams into the relationship between two plumage phenotypes, pied and mottled, both of which are arrangements of non-pigmentation expressed on a background of eumelanin. 2. Both the pied and mottled phenotypes had previously shown to be caused by recessive genes, denoted pi and mo respectively. 3. The progeny consisted entirely of intermediaries between the two parental phenotypes, indicating that pi and mo are one and the same gene for which I retain the symbol mo.     

Chocolate: A sex‐linked recessive plumage colour mutant of the domestic fowl

1. A mating between Black Orpington bantams produced, in addition to blacks, a single female in which the black colouration was replaced by dark chocolate.

2. A mating of the chocolate‐coloured female with a black male, F₂ and backcross matings demonstrated that the chocolate phenotype is caused by a recessive sex‐linked gene to which I assign the symbol ?CHOC.

3. A mating of ‘chocolates’ inter se yielded all chocolate offspring.     

Relationship between genes at the pea and single comb locus and economic traits in broiler chicken

Six hatches of pedigreed broilers, comprising a total of 7593 birds from 223 Cornish‐type sires, 112 homozygous and 111 heterozygous for pea comb, were used to study the effect of comb type on final weight, frequency of breast blisters and carcass yield.

Contrary to results reported in the literature there was no evidence of an association between comb type and broiler growth.

Single comb broilers showed a lower incidence of breast blisters than their siblings with pea combs. This difference was highly significant in males and less so in female broilers. It is suggested that this might be another manifestation of the pea comb allele, possibly as a result of structural changes in the skin. For a given weight, females had a significantly lower frequency of breast blisters than males, indicating a direct influence of sex on breast blister formation apart from the immediate effect of body weight.

Broilers with pea comb had a slightly better carcass yield than single comb broilers.     

Inheritance of the lace‐tailed laced plumage pattern of the sebright bantam

1. An investigation was conducted firstly among progeny from a cross between Blue Andalusian and Silver‐spangled Hamburgh bantams, and secondly between crosses of selected progeny of this mating with a Silver Sebright bantam in an effort to determine the genotype of the lace‐tailed laced plumage phenotype of the latter.

2. The genotype of the black‐laced blue and the spangled plumage phenotypes of the Andalusian and the Silver‐spangled Hamburgh had, respectively, been shown to depend on homozygosity of E, Co, db⁺, Ml and Pg, and of co⁺, Db, Ml and Pg together with a black down allele at the E‐locus presumed to be E, but also hypothesised to be E^R. The genes E and E^R are the extended black and birchen‐like allele at the E‐locus whilst Co, Db, Ml and Pg are, respectively, the eumelanin restrictors, Columbian and dark‐brown Columbian, the eumelanin extension melanotic and the pattern gene. The Sebright had been hypothesised to possess the E allele at the E‐locus, and to be homozy‐gous Co, Ml and Pg, a combination shown to be responsible for the black‐tailed laced phenotype of the Wyandotte.

3. Segregation in the F₂ generation varied from that expected if both parental genotypes were E/E, but gave close agreement if the Silver‐spangled Hamburgh was E^R/E^R.

4. A lace‐tailed laced segregant in the F₂ generation of the first mating, presumed to be homozygous E^R, Co, Db, Ml and Pg was mated to a Sebright. The F₁ generation failed to segregate at the 5 loci, thus suggesting the genotype of the lace‐tailed laced phenotype of the Sebright to be homozygous E^R, Co, Db, Ml and Pg. Segregation in the F₂ generation of a mating of the female F₁ with a Silver‐spangled Hamburgh male confirmed the genotype of the lace‐tailed lacing of the Sebright bantam, and demonstrated that of the Silver‐spangled Hamburgh to be homozygous E^R, co⁺, Db, Ml and Pg‐.