Showing papers in "Journal of Heredity in 1978"

B-A translocations in maize I. Use in locating genes by chromosome arms

Abstract: HE B-A TRANSLOCATIONS of maize (Za mayvs L.) provide a most efficient method for T locating recessive mutants to the proper chromosome arm. More comprehensive knowledge of gene location should permit efficient assembly of genotypes for improving photosynthetic rate and disease reaction and for other practical goals.

Inheritance of the horned, scurred, and polled condition in cattle

Abstract: THE mode of inheritance of the horned, scurred, and polled condition in cattle has been reported by several workers. White and Ibsen presented a hypothesis that included four independent loci to explain their observations and reports in the literature up to the time of their study. Their hypothesis, which is the most complex that has been proposed for the inheritance of these characteristics, included the following model: 1) P—completely dominant gene for the polled condition, completely epistatic to horns (H) in both sexes; p—the absence of P. 2) H—gene for horns; always present in both sexes in the homozygous state and epistatic to the gene for scurs (Sc). h—does not exist in domestic cattle. As pointed out by Shrode and Lush, this locus serves only to symbolize the genetic complex that makes them cattle. 3) Ha—African horn gene epistatic to P in males; not certain in females. It is present in most breeds but is at a low frequency in many breeds. This gene does not modify the expression of horns on an otherwise horned animal. ha—the absence of Ha. 4) Sc—the gene for scurs. The expression of this gene is sex-influenced. The heterozygote (Scsc) is usually scurred in males, but only the homozygote (ScSc) is scurred in females. White and Ibsen assumed that these four genes segregated independently. Other workers have postulated that only one locus is involved in the inheritance of the horned, scurred, and polled condition. Spillman as well as LloydJones and Evvard interpreted the gene for polled (P) to be dominant to the gene for horns and many of the heterozygotes of both sexes to be scurred. Watson 9 interpreted the gene for polled to be completely dominant in females and horns to be inhibited, but not completely suppressed, in heterozygous males; he also interpreted the level of suppression to vary among breeds. Cole reported results indicating that the polled condition is inherited as dominant to horns and that scurs occur more frequently

Inheritance of resistance to white mold disease in Phaseolus coccineus

Abstract: S EPIDEMICS of white mold of snap bean {Phaseolus vulgaris L.), caused by Whetzelinia (=Sclerotinia) sclerotiorum (Lib) Korf and Dumont, have occurred repeatedly in central and western New York State in recent years. The disease has caused significant economic losses, especially during prolonged periods of wet weather-. White mold epidemics in New York are initiated by ascospores produced mainly outside bean fields by sclerotia of the fungus'. Ascospores do not directly infect bean tissues in the prebloom stage, since blossoms are needed as an energy source for germination and infection '•'-. A prolonged period of wet soil is required for the production of ascospores, and 48-72 hours of continuous moisture is required for initiation of infection''. The fungus completely colonizes mature and senescent blossoms in 2-3 days. These infected blossoms then serve as an efficient source of inoculum when in contact with leaf, stem, and pod tissues. Chemical control of this disease with benomyl has been successful ', but its relatively high cost, the rigidity of the spray program, and the threat of the development of a benomyl-resistant strain of the pathogen have stimulated the search for sources of resistance in P. vulgaris and other Phaseolus species. A large number of cultivars, breeding lines, and plant introductions were evaluated using an inoculation technique and conditions that simulated natural infection (Abawi et al.; Abawi et al., unpublished data). All the accessions of P. vulgaris were susceptible, although a few plants of some lines appeared to be tolerant. However, a high degree of resistance was found in selections of P. coccineus, including a white-flowered line, B-3749, a selection of P.I. 175829. This line and other accessions of P. coccineus had been found resistant to white mold by Adams et al. using a different inoculation procedure. Recently, Coyne et al. reported that Black Turtle Soup was the most resistant dry bean germplasm to the white mold fungus under natural inoculation conditions in western Nebraska. This paper reports the inheritance of resistance in line B-3749 to W. sclerotiorum and the progress made in transferring the resistance to two commercial snap bean cultivars.

Phaeomelanin synthesis and obesity in mice. Interaction of the viable yellow (Avy) and sombre (eso) mutations.

Abstract: Is abnormal regulation of phaeomelanin synthesis, which results in yellow coat color, inextricably linked to the development of obesity in viable yellow (Avy) house mice? To answer this question, black male mice of genotypes Avy/A eso/e+ and A/ae eso/e+ were produced from (DFT/Wf X C3H-1 vyfB/HeWf X SO/LeWf matings. The sombre (eso) mutation prevents phaeomelanin synthesis; therefore, all mice carrying this dominant allele are black regardless of the alleles present at the agouti locus. These black males were weighed weekly to 18 weeks of age. Simultaneously the agouti locus genotype of each male was determined by test matings to a/a e+/e+ females. The results of these test matings indicated that the two genotypes could be classified rather accurately by the intensity of pigmentation of the belly hair. Black Avy mice tended to have more dilute belly pigmentation that black A/ae mice. These gross observations were confirmed by microscopic examination of several hair types. Black Avy males reached a mean body weight of 44.2 +/- 0.6 g at 18 weeks, while black A males had a mean weight of 30.7 +/- 0.4 g at the same age. It is concluded that excessive weight gain resulting in obesity is induced by the Avy gene even when phaeomelanin synthesis is completely inhibited.

Linkage of tobiano coat spotting and albumin markers in a pony family

Abstract: Genetic segregation patterns among blood type markers and various phenotypically observed traits were studied in a small herd of ponies. The herd consisted of 10 mares without white spotting and a single stallion with the dominant pattern of tobiano spotting. Comparison of segregation patterns at loci for which the stallion was heterozygous showed tight linkage for the Alb-B and tobiano markers. In 17 cases in which the Alb contribution of the sire could be determined, all 10 foals that inherited AlbB from him were tobiano spotted, and all 7 non-spotted foals inherited his AlbA. The use of the symbol To is proposed for dominantly inherited tobiano spotting linked to the albumin.

Microwave radiation-induced chromosomal aberrations in corneal epithelium of Chinese hamsters

Abstract: A microwave diathermy machine was used to irradiate the eyes of 5-month-old female Chinese hamsters. The right eye of each of seven animals was irradiated with 75 mW/cm2 radiation density for 10 minutes. After one month, slit-lamp examinations revealed lens opacities in the exposed eyes of two animals. Next, the right eye of each of 32 animals was irradiated with 100 mW/cm2 radiation density for 30, 20, 10, or 5 minutes. Epithelial cells of the cornea were collected to make chromosomal preparations. There were 0.1562, 0.0794, 0.0819, and 0.0488 chromosomal breaks per cell, respectively. No chromosomal breaks were observed in three sham-exposed animals. The percentage of abnormal cells and the number of chromosomal breaks per cell in animals that had exposures of 100 mW/cm2 radiation density for 30 minutes were higher than those in control animals. These results were statistically significant at the 5 percent level.

A sex-transformation gene in Drosophila melanogaster

Abstract: A sex-transformation gene, tra-2OTF, of Drosophila melanogaster is described. The gene is an allele of tra-2 (transformer-2, 7--70+/-), acts only on XX individuals and transforms them into morphologically nearly normal but sterile males. Neither a male-specific lethal gene mle nor the male-killing maternally transmitted infectious SR-agent have any effect on the tra-2OTF transformed flies. External as well as internal reproductive organs of tra-2OTF transformed flies, except for the gonads, are male. The gonads, which are yellowish-colored rudimentary testis-like structures in tra-2 transformed flies, are rudimentary ovaries without yellowish coloration that sometimes develop to near maturity. Numbers of bristles in each of the female pattern in tra-2OTF and tra-2OTF/tra-2 transformed flies, while these bristles are of the male pattern in tra-2 transformed flies. Furthermore, the sixth abdominal sternite, which in normal males as well as in tra-2 transformed males lacks bristles, bears numbers of bristles in tra-2OTF and tra-2OTF/tra-2 transformed flies.

Mus musculus x mus caroli hybrids: mouse mules.

Abstract: Analysis of six enzymes using starch gel electrophoresis indicates that autosomal and X-linked genes of both parental species are expressed normally in M. musculus X M. caroli hybrids. There is no evidence for allelic repression for the four autosomally inherited enzymes. Banding patterns for G6PD and PGK-1 indicate that X-chromosome inactivation occurs and that the maternally derived M. musculus X-chromosome is preferentially expressed in the yolk sac. Despite normal genetic expression none of the four adult female hybrids was fertile and the male hybrids tended to be retarded during fetal development. The routine production of fetal M. musculus X M. caroli hybrids, heterozygous for three X-linked genes coding for G6PD, PGK-1, and HPRT, should provide an excellent system for the analysis of X-chromosome expression and an alternative to the mule for studies of hybrid reproduction and development.

Identification of inbred strains of mice. II. Characterization of different substrains of the c3h strain.

Abstract: Substrains of inbred C3H mice differ significantly in their genetic constitution with respect to biochemical markers, skin grafting, and skeletal variations. The presence of such discrepancies among substrains poses a problem when comparing conclusions based on experiments done in different substrains. Therefore, methods of controlling the genetic constitution are necessary and important to avoid these discrepancies.