Linkage of Pgm-3 in the house mouse and homologies of three phosphoglucomutase loci in mouse and man

The discovery of a third phosphoglucomutase locus (Pgm-3) in the house mouse is reported. Three alleles are recognized on the basis of differences in electrophoretic mobility and enzymatic activity. Pgm-3 ^a (fast mobility and high activity) is present in inbred strain C57BL/10J and 24 other strains; Pgm-3 ^b (slow mobility and high activity) is present in LP/Pas and six other strains; and Pgm-3 ^c (no detectable activity in any tissue tested) is present in strain DBA/2J and 14 other strains. Seventy-four recombinant inbred strains derived from progenitors that differed at Pgm-3 were used to study genic linkage. Pgm-3 is on chromosome 9 and is linked to Sep-1, d, Mod-1, and Ltw-3. Gene order and recombination frequencies are estimated as d 3.8±1.8% Pgm-3 2.3±1.2% Mod-1. Substrate specificities and cofactor requirements show that mouse Pgm-1 is homologous with human Pgm-2, mouse Pgm-2 with human Pgm-1, and mouse Pgm-3 with human Pgm-3.This research was supported in part by NIH Research Grant GM18684 from the National Institute of General Medical Sciences to B.A.T. and by grants from NIH A105531-02 and the Volkswagon Foundation to Jan Klein. J.H.N. was a recipient of a Fellowship from the Max-Planck-Gesellschaft, Munich. G.S. and J.K. were supported by funds from the Deutsche Forschungsgemeinschaft.     

A null mutation at the mouse Phosphoglucomutase-1 locus and a new locus,Pgm-3

A null mutation at the phosphoglucomutase locus (Pgm-1) was discovered by electrophoretic analysis of the inbred mouse strain C57 BL/6J. The null allele (Pgm-1 ⁿ) was shown to segregate as a Mendelian unit alternative to the Pgm-1 ^a and Pgm-1 ^b alleles. Mice expressing the Pgm-1 ⁿ allele, either in the heterozygous or homozygous state, are viable, healthy, and fertile. The occurrence of the Pgm-1 ⁿ mutant revealed a previously unreported genetic locus (Pgm-3) that controls the expression of a third phosphoglucomutase. Two electrophoretically expressed alleles of Pgm-3 (inherited without dominance) are found in the inbred mouse strains C57 BL/6J and DBA/2J. Linkage observed between the Pgm-3 locus, the dilute locus (d) and the cytoplasmic malic enzyme locus (Mod-1) has allowed assignment of the Pgm-3 locus to chromosome 9. A striking tissue specific expression of Pgm-1 and Pgm-3 was observed. Products of the Pgm-3 locus were detected in kidney, testes, brain, and heart. In contrast, Pgm-1 controlled isozymes were present in kidney, spleen, ovaries, and erythrocytes.Financial support for this work was provided in part by Contract #263-78-C-0393 from the National Institute of Environmental Health Sciences to the Research Triangle Institute.     

Linkage of isozyme loci in the mouse: Phosphoglucomutase-2 (Pgm-2), mitochondrial NADP malate dehydrogenase (Mod-2), and dipeptidase-1 (Dip-1)

The linkages of the isozyme genes Mod-2, Pgm-2, and Dip-1 have been determined in tests with established linkage group markers among inbred strains of mice. Unique alleles for both Mod-2 and Pgm-2 have been observed in the strain of SM/J. Linkage was determined from backcross progeny of the matings C57BL/6J×(SM/J×C57BL/6J)F₁, (SM/J×SWR/J)F₁×SM/J, and (SM/J×SWR/J)F₁×SJL/J. The gene Mod-2 is on linkage group 1. In a three-point cross of the loci Gpi-1, c, and Mod-2, the c locus was determined to be the middle gene. No double crossovers were observed. Our combined data show the following linkages: Gpi-1 to c, 28.3±3.2%; Gpi-1 to Mod-2, 33.3±3.0%; and c to Mod-2, 4.1±2.8%. The proposed gene order for four markers on LG I is Gpi-1-p-c-Mod-2. The gene Pgm-2 was linked to Gpd-1 (27.0±4.2%) on LGVIII. Two backcrosses segregating for Pgm-2 and b, (SM/J×DBA/2J) F₁×DBA/2J and (SM/J×DBA/2J)F₁×C57BR/cdJ, showed 9.1±4.3% recombination. The proposed gene order on LG VIII is b-Pgm-2-Gpd-1. The genes Pgm-1 and Pgm-2 are not linked (53.4±4.4%). Linkage of the isozyme genes Dip-1 and Id-1 on LG XIII was observed in backcross progeny of the crosses (SJL/J×C57BL/6J)F₁×SJL/J and C57BL/6J×(SM/J×C57BL/6J)F₁. The combined recombination was 23.8±2.8%. Two cases are established where genes whose enzyme products share substrate affinities (Pgm-1 and Pgm-2; Mod-1 and Mod-2) are not linked. Our data generally support the conclusion that functionally or metabolically related isozyme genes are not contiguous on mouse linkage groups.This investigation was supported in part by Public Health Service General Research Support Grant GM-09966 and in part by Public Health Service Training Grant 5T01 HD-00032-07 from the National Institute of Child Health and Human Development, and by Atomic Energy Commission contract AT(30-1)-3671.     

Phosphoglucomutase electrophoretic variants in the mouse

The phosphoglucomutase (PGM) electrophoretic phenotype of the mouse (Mus musculus) consists of several distinct components which can be grouped into two major zones designated PGM-1 and PGM-2. Evidence presented here indicates that each zone is controlled by a single genetic locus denoted Pgm-1 and Pgm-2, respectively. Two variant forms segregated at the Pgm-1 locus. They were codominantly expressed and inherited as alleles at an autosomal locus. The alleles were termed Pgm-1 ^a (fast) and Pgm-1 ^b (slow). These alleles were separately fixed in a number of inbred strains of mice. Preliminary evidence based on wild mouse phenotypes indicates that variant forms also exist for PGM-2 which are inherited as alleles at an autosomal locus. Genetic linkage relationships have not been determined for these loci. PGM-1 variants and PGM-2 were expressed in mouse fibroblasts in vitro.Supported by U.S. Public Health Service grants GM-09966 and GM-07249 from General Medical Sciences and 5 F2 HD-35,531 from Child Health and Human Development; and Atomic Energy Commission contract AT(30-1)-3671.Postdoctoral Fellow of the U.S. Public Health Service.     

Identification and genetic control of two rabbit low-density lipoprotein allotypes

Rabbits were immunized with a low-density lipoprotein (LDL) preparation isolated from rabbit serum by ultracentrifugation. This elicited precipitin isoantibodies which distinguished two antigenically different genetic variants, i.e., allotypes of serum LDL. Both allotypes were identified as LDL by the following criteria: (1) the precipitin lines stained intensely with the lipid stain Sudan black B; (2) the antigens were found in the low-density but not the high-density lipoprotein fraction; (3) the antigens migrated electrophoretically on Agarose in the ₂ to region. That the inheritance of these two allotypes is controlled by a pair of allelic genes at an autosomal locus is based on allotypes present in 323 progeny from six possible mating combinations. This LDL locus designated Lpqwas shown not to be linked to the light-chain or heavy-chain loci of immunoglobulins. This investigation was supported (in part) by NSF Grant GB-5536 and USPHS Grant AI07043-03.Supported by USPHS predoctoral fellowship (1-F1-GM-37, 211-01) from the National Institute of General Medical Sciences.     

Genetics of formamidase-5 (brain formamidase) in the mouse: Localization of the structural gene on chromosome 14

A single formamidase, which is different from the formamidases found in other tissues, occurs in the brains of mice. This enzyme is here called formamidase-5 and the gene symbol is designated For-5. Two alleles are recognized on the basis of their differential heat sensitivity: For-5 ^b is relatively heat stable and is present in strain C57BL/6J, while For-5 ^d is relatively heat sensitive and is present in strain DBA/2J. The heat sensitivity of formamidase-5 in 44 other inbred strains and substrains was tested and found to resemble that of C57BL/6J or DBA/2J. Thirty-six recombinant inbred strains derived from progenitors that differed at For-5 were studied to test for single-gene inheritance and linkage with other loci. Complete concordance was found with the esterase-10 locus (Es-10), indicating close linkage. The 99% upper confidence limit of the distance between For-5 and Es-10 is 3.7 centimorgans (cM). Es-10 is located on chromosome 14 about 19 cM from the centromere. An independent demonstration of linkage of For-5 with Es-10 and another chromosome 14 marker, hairless (hr), is provided by the finding that the HRS/J strain, which has been sibmated for 60 generations with forced heterozygosity at the hr locus, is cosegregating at For-5 and Es-10. A survey of 32 inbred strains and substrains revealed that the For-5 ^d allele is associated with the Es-10 ^b allele, and that the For-5 ^b allele is associated with Es-10 ^a and Es-10 ^c. Formamidase-5 segregates as expected in the F₂ generation of crosses between strains bearing For-5 ^b and For-5 ^d alleles. It is possible that this unique formamidase of the brain is involved in the metabolism of a neurotransmitter substance.This research was sponsored in part by the Department of Energy under contract with the Union Carbide Corporation and in part by NIH Research Grant GM-18684 from the National Institute of General Medical Sciences. J. C. F. is a predoctoral Fellow supported by Grant CA 09104 from the National Cancer Institute. The Biology Division of Oak Ridge National Laboratory and the Jackson Laboratory are fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

Mouse aldehyde dehydrogenase genetics: Positioning of Ahd-1 on chromosome 4

Electrophoretic variants of mitochondrial aldehyde dehydrogenase (AHD-A₂) are widely distributed among inbred strains of Mus musculus and have been used to localize the gene encoding AHD-A₂(Ahd-1) at the non-centromeric end of chromosome 4. In the mouse (Mus musculus), aldehyde dehydrogenase (AHD; E.C.1.2.1.3) exists as at least three isozymes which are differentially distributed in liver subcellular fractions (designated A₂, B₄ and Cy* for the mitochondrial, soluble and microsomal isozymes respectively) and in various tissues of this animal (Holmes, 1978a; 1978b; Timms & Holmes, 1981). Electrophoretic variants have been previously reported for the A₂ and B₄ isozymes among inbred strains of mice, and the genetic loci (designated Ahd-1 and Ahd-2) have been localized on chromosomes 4 and 19 respectively (Holmes, 1978b; Timms & Holmes, 1980). This paper describes further genetic analyses of AHD-A₂ enabling Ahd-1 to be positioned at the non-centromeric end of chromosome 4. Forty-three inbred strains of Mus musculus were used in these studies (Table 1). Two series of matings were carried out. 1) Female SM/J mice and male NZC/B1 mice were mated to obtain F, female offspring which were backcrossed to male NZC/B1 mice. These progeny were used to examine the segregation and linkage relationship of b (brown), Pgm-2 (encoding phosphoglucomutase B) and Ahd-1 (Table 2). 2) Female C57BL/6J mice and male SM/J. mice were mated to obtain F, female offspring which were backcrossed to male SM/J mice. The segregation and linkage relationship of Pgm-2, Gpd-1 (encoding the liver and kidney isozyme of hexose-6 phosphate dehydrogenase) and Ahd-1 were examined for these backcross progeny (Table 3). Methods for preparing liver and kidney extracts and the cellulose acetate electrophoresis procedure for typing Ahd-1, Pgm-2 and Gpd-1 have been previously described (Holmes, 1978b). A previous study has described the electrophoretic patterns for allelic variants for mitochondria1 AHD and of the hybrid phenotype for this enzyme (Holmes, 1978b). The three-allelic isozyme pattern for hybrid animals was consistent with a dimeric subunit structure: AHD-A¹A², AHD-A¹A² and AHD-3, with the A1 and A2 subunits being encoded by separate alleles at a single locus, designated Ahd-1 (Ahd-1^oand Ahd-1^brespectively). The distribution of these alleles among 43 inbred strains of mice is given in Table 1. The allelic variants were approximately equally distributed among the inbred strains examined and no divergence of phenotype was observed among the 6 substrains of C57BL mice (Ahd-1^aallele) and 5 substrains of BALB/c (Ahd-1^ballele) mice examined. Genetic variants for phosphoglucomutase-B (PGM-B) have been reported by Shows, Ruddle and Roderick (1969) and the gene (Pgm-2) was subsequently localized on chromosome 4 near b (brown) by Chapman, Ruddle and Roderick (1970). Table 2 illustrates the results of a three-point cross between b, Pgm-2 and Ahd-1. Variation from the expected 1:1:1:1:1:1 ratio for unlinked loci was significant(x²= 73.15; 7 df; P < 1 × 10^-5), indicating that the three loci are linked. Recombination frequency data are consistent with the gene order: b - Pgm-2 - Ahd-1 The second cross examined the segregation of Pgm-2, Ahd-1 and Gpd-1 loci (Table 3). The latter locus has been previously positioned on chromosome 4 (linkage group VIII) by Hutton & Roderick (1970) and Chapman (1975), and has been used to localize Ahd-1 in this region (Ahd-1 and Gpd-1 exhibit a recombination frequency of 10.3 ± 3.7 %) (Holmes, 1978b). The data from Table 3 is consistent with a gene order of Pgm-2 - Ahd-1 - Gpd-1. The recombination frequency data of Ahd-1 with Gpd-1, Pgm-2 and b also supports the proposal that Ahd-1 is localized between Pgm-2 and Gpd-1 (Tables 2 and 3; Holmes, 1978b). Recent metabolic studies have indicated that mitochondria1 aldehyde dehydrogenase (AHD) plays a very important role in the metabolism of acetaldehyde derived from ethanol, ensuring a low concentration of acetaldehyde in the blood leaving the liver (Grunnet, 1973; Parilla et al., 1974; Corral1 et al., 1976). Moreover, genetic variation of this isozyme in human livers has been recently reported (Harada et al., 1978), and this polymorphism has been proposed as the molecular basis for individual and racial differences in alcohol sensitivity (Goedde et al., 1979). Consequently, genetic analyses of mitochondria1 AHD are of particular significance to studies on the genetic control of alcohol metabolism in mammals. In summary, this report confirms previous studies which demonstrated that the genetic locus encoding mitochondrial aldehyde dehydrogenase in the mouse (Ahd-1) is on chromosome 4 (Holmes, 1978b), and positions the gene with respect to b (brown), Pgrn-2 (encoding phosphoglucomutase B) and Gpd-1 (encoding the liver and kidney isozyme of hexose-6-phosphate dehydrogenase). In addition, the distribution of the 2-allelic phenotypes for this isozyme has been examined among 43 in- bred strains of mice.     

Frequency-Dependent Selection at the PGM-1 Locus of DROSOPHILA PSEUDOOBSCURA

Frequency-dependent fitness was studied at the Pgm-1 locus of Drosophila pseudoobscura with respect to two fitness components: rate of development and larva-to-adult survival. The Pgm-1 locus is very polymorphic with only two alleles, Pgm-1¹⁰⁰ and Pgm-1¹⁰⁴, occurring at high frequencies. For each of these two alleles, 20 homozygous strains were obtained from a sample of 1,140 wild-inseminated females. First-instar larvae of the two genotypes were combined in a set of eight different frequencies: 0.0, 0.10, 0.25, 0.40, 0.60, 0.75, 0.90, and 1.0. Frequency-dependent fitness effects were observed for the two survival-related fitness components examined: larvae of the less common genotype develop faster and have a higher probability of survival than larvae of the more common genotype. The rate of survival at intermediate genotypic frequencies is similar to that in pure cultures. If selection acted solely as frequency-dependent effects on survival-related components of fitness, the equilibrium frequency of the Pgm-1¹⁰⁰ allele would be 0.615 for a two-genotype system, which fits an observed frequency range for this allele in nature between 0.55 and 0.71. Experimentally created linkage disequilibrium was excluded from the experiment by using a large number of independent strains. It is nevertheless possible that the frequency-dependent selection may not affect the Pgm-1 locus per se, but may reflect a linkage disequilibrium present in the natural population. Even if this were the case, the frequency-dependent selection could affect the frequency of the Pgm-1 alleles in nature.     

Adh n5: A temperature-sensitive mutant at the Adh locus in Drosophila

Individuals of an alcohol dehydrogenase-negative strain of Drosophila melanogaster designated Adh ⁿ⁵ are resistant to ethanol poisoning at low but not at high temperatures. The basis for this behavior is that Adh ⁿ⁵ flies contain a mutant form of alcohol dehydrogenase which is less heat stable than that of wild-type flies. The mutation in Adh ⁿ⁵ maps at, or very close to, the presumptive structural locus and is not complemented by any of 11 other alcohol dehydrogenase-null mutants.This research was supported by Grant No. GM 18254 from the National Institutes of Health and Grant No. M55.2217 from the National Cancer Institute.Publication No. 768 from the Department of Biology, Johns Hopkins University.     

Inheritance and linkage relationships of ten isozyme genes in hazelnut

Summary The inheritance of 6-phosphogluconate dehydrogenase (6PGD), malate dehydrogenase (MHD), aconitase (ACO), phosphoglucomutase (PGM), phosphoglucoisomerase (PGI), and glutamate-oxalacetate transaminase (GOT) polymorphic isozymes was studied in leaf extracts of nine hazelnut progenies using horizontal starch gel electrophoresis. Evidence of Mendelian inheritance was obtained for ten loci: 6-Pgd-2, Mdh-1, Aco-1, Aco-2, Pgm-1, Pgm-2, Pgm-3, Pgi-2, Pgi-3, and Got-2, which permitted the analysis of 28 alleles (2.8 per locus). The presence of null alleles was detected in Pgm-1 and Pgm-3. Joint segregation analysis of pairs of isozymes revealed four linkages: Mdh-1-Pgi-2, Aco-2-Pgm-2, Pgm-1-Pgm-3, and 6Pdg-2-Pgm-2.     

Strain distribution and linkage relationship of a mouse embryonic hemoglobin variant

Search for structural variants of three globin chains (x, y, z), synthesized only during mouse embryonic hematopoiesis, was carried out by electrophoretic analysis of blood from 12-day embryos, all with C57BL/6 mothers, and fathers from 115 inbred stocks selected for their diverse genetic origins. Structure of the -chains of adult hemoglobins differed among the tested strains, with 57 carrying the Hbb ^sallele, 56 the Hbb ^dallele, and two the Hbb ^pallele. The search revealed no x- or z-chain variants but confirmed and extended knowledge of a previously described y-chain variant. Blood of all embryos sired by males from the 57 Hbb ^sstrains contained only y¹-chains, while blood of all embryos sired by Hbb ^dor Hbb ^pmales contained y2-chains as well as the y¹-chains inherited from their C57 BL/6 mother. The locus controlling structure of the y-chain of mouse embryonic hemoglobins is thus extremely closely linked to the locus controlling structure of adult hemoglobin -chain, with maximum possible recombination frequency less than 0.019.This work was supported in part by Grants CA-01074 from the National Cancer Institute, USPHS, and GM 18684 from the National Institute of General Medical Sciences, in part by Grant ACS-VC58 from The American Cancer Society, in part by grants to the Jackson Laboratory from the Bushrod H. Campbell and Adah F. Hall Charity Fund and the Robert Sterling Clark Foundation, and in part by the Jackson Laboratory Endowment Fund. The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

Teratocarcinoma transplantation rejection loci: Genetic localization of the Gt-1 locus on chromosome 17 and the expression of alternate alleles

A series of congenic mice on the BALB/c genetic background have been employed to localize a teratocarcinoma transplantation rejection locus, Gt-1, to the K side of the H-2 locus on chromosome 17. Previous studies have placed the Gt-1 ^sv allele about 8 centimorgans away from the H-2 ^b or H-2 ^bv1 locus. Teratocarcinomas derived from 129/sv mice, Gt-1 ^sv (H-2K ^bv1/H-2D ^bv1), are rejected by BALB/c (H-2K ^d/H-2D^d) and BALB-G mice (H-2K ^d/H2D-^b, but form tumors in BALB-B (H-2K ^b/H2D ^b) and BALB/5R5 mice (H-2K ^b/H2D ^d). In the reciprocal tumor-rejection test, a BALB/c teratocarcinoma was rejected by immunized BALB·B mice, but formed tumors in the immunized isogenic BALB/c mouse. These studies demonstrate the reciprocal expression of two Gt-1 alleles, one Gt-1 ^c, in BALB/c mice, and the other, Gt-1 ^sv, in the congenic BALB·B mice. Shedlovsky and co-workers have placed the Gt-1 locus in a similar location on the K side of the H-2 locus on chromosome 17.     

Genetics of an esterase in Aedes aegypti

Zymograms of single individuals of Aedes aegypti were obtained by means of starch gel electrophoresis, using alpha-naphthyl acetate as substrate. Inbred lines gave consistently homogeneous patterns; earlier results from random-breeding laboratory strains had shown considerable variability. Six distinct bands were observed. The furthest moving band, designated Esterase 6, showed differential migration in two inbred lines. Reciprocal crosses between these lines gave F₁ progeny showing both bands. Backcrosses of F₁ to either parental line gave a 1:1 segregation. These results are consistent with the hypothesis that the two forms of Esterase 6 are controlled by a single pair of codominant alleles at a single gene locus (Est 6 ^a and Est 6 ^b). Linkage tests with marker genes have demonstrated that Est 6 is on linkage group 2, with the following alignment: spot-abdomen (9.0±1.0) yellow-larva (17.4±1.3) Est 6. Crosses with another inbred line demonstrated a third band with intermediate mobility, designated Est 6 ^c. An additional electrophoretic variant which seems to have a simple Mendelian basis was found in esterase band 1.This work was supported by NIH Research Grant No. A1-02753.     

Cytogenetic studies in barley chromosome 1 by means of telotrisomic,acrotrisomic and conventional analysis

Summary Genetic and cytogenetic techniques were applied to linkage analysis of chromosome 1. Eight marker genes, including five on the short arm and three on the long arm, were analyzed with two telotrisomic lines, Triplo 1S and 1L, and one acrotrisomic line, Triplo 1L^1S. Telotrisomic analysis confirmed the position of a _c 2, gs3, f3, br, f5, and f8 on the short arm, and 1k2 and n on the long arm of the linkage map of chromosome 1. Conventional three-point tests with two triple genetic marker stocks showed that f _c is located between br and gs3, and n is located in the middle of f8 and 1k2. Acrotrisomic for 1L^1S was used for cytogenetic linkage mapping. Giemsa N-banding technique showed that the long (1L) and short (1S) arm had deficiencies of 37.5% and 73%, respectively. Genes f5, br, f _c, gs3 and f8 in 1S and 1k2 in 1L were located in the deficient segments of 1L^1S. A trisomic ratio obtained with n indicated an association of this gene with the long arm of the acrocentric chromosome. Cytological behavior, morphological characteristics, fertility, and transmission in the acrotrisomic 1L^1S are also reported.Contribution from Department of Agronomy and published with the approval of the Director of Colorado State University Agricultural Experiment Station. Series No. 2984. Supported by USDA Competitive Research Grant No. 82-CRCR-1-1020, USDA-CSU Cooperative Research Grant No. 58-9AHZ-2-265 and Colorado State University Hatch project     

A map of rye chromosome 4R with cytological and isozyme markers

The progeny of two crosses between a structural heterozygote for a reciprocal translocation (4RL/5RL) and a homozygote for the standard chromosome arrangement and of four crosses between standard chromosome homozygotes were analysed in rye (Secale cereale L. cv Ailés) for the electrophoretic patterns of five different leaf and endosperm isozymes (LAP, PGM, NDH, ADH and EPER). The presence or absence of the quadrivalents at metaphase I (MI) was also tested. Loci Adh-1, Pgm-1 and Ndh-1 were located on chromosome arm 4RS, and locus Eper-1 on chromosome arm 4RL. Locus Lap-2 was located on the 4RS chromosome arm. The estimated distances among the different linked loci support the following gene order: Eper1¨ (breakpoint-centromere)¨Lap-2¨ ¨Adh-1 ¨Pgm-1¨Ndh-1. These results provide evidence for the chromosomal location of Lap-2 locus on chromosome arm 4RS in cv Ailés. A high negative interference was detected between the zones delimited by centromere and Lap-2, and Lap-2 and Pgm-1 in plants with the 4RL/5RL translocation.Abbreviations LAP leucine aminopeptidase - PGM phosphoglucomutase - NDH NADH dehydrogenase - ADH alchohol dehydrogenase - EPER endosperm peroxidase     

SIMPLE GENETIC BASIS FOR IMPORTANT SOCIAL TRAITS IN THE FIRE ANT SOLENOPSIS INVICTA

Variation in queen phenotype and reproductive role in the fire ant Solenopsis invicta has been shown to have a simple genetic basis in a single introduced population in the United States. The evidence consists of an association between this variation and queen genotype at Pgm-3, a phosphoglucomutase-encoding gene. In the present study, we surveyed Pgm-3 allele and genotype frequencies in diverse populations from the native and introduced ranges of this ant to learn whether this simple genetic basis for reproductive traits is a general feature of the species or a genetic anomaly in introduced ants stemming from a recent bottleneck or the invasion of novel habitats. No egg-laying queens living in polygyne (multiple-queen) nests possessed the homozygous genotype Pgm-3^a/a in any of the study populations, yet nonreproductive females from such nests (workers as well as queens that had not yet initiated oogenesis) possessed this genotype at moderate frequencies. Remarkably, Pgm-3^a/a was the most common genotype among all classes of females, including egg-laying queens, in monogyne (single-queen) nests from all populations studied. Genotype proportions at Pgm-3 in polygyne populations typically departed strongly from the proportions expected under Hardy-Weinberg equilibrium, whereas those in monogyne populations did not. These patterns establish that a single mendelian gene influences queen reproductive role in S. invicta and that this gene uniformly is under strong directional selection in the polygyne social form only. Moreover, the perfect association of Pgm-3 genotype and reproductive role in all populations, combined with the known function of phosphoglucomutase in insect metabolism, suggest that this gene may directly influence queen phenotypes rather than merely serving as a marker for a linked gene that causes the effects.     

Linkage relationships and chromosomal locations of enzyme-coding genes in pepper,Capsicum annuum

The linkage relationships and chromosomal locations of 14 enzyme-coding genes were investigated in Capsicum annuum L. (garden pepper) by monitoring segregations in backcross and F₂ progeny of an interspecific cross between C. annuum cv. NM6-4 and C. chinense CA4 and by studying allele dosage effects in five hybrid primary trisomics. These conclusions can be reached: 6Pgdh-i is on the metacentric chromosome corresponding to the noir trisomie; Idh-1 and Est-3 are on chromosome 12; an aerocentric chromosome which corresponds to the pourple trisomie; Idh-1 is near the centromere and Est-3 is distal on the long arm of that chromosome. The other loci can be arranged in the following linkage groups and are apparently not located on the trisome corresponding to any of the trisomics tested: Est-4-18cM-(Pgi-1-3cM-Pgm-1); Prx-7-2cM-Tk-1; Pgm-2-2cM-Skdh-1; Est-1-OcM-Est-7. Linkage and dosage data combined with karyotype and meiotic analyses of the two species and F₁ hybrids suggest that Idh-1 and Skdh-1/Pgm-2 are near the breakpoints on the two chromosomes involved in a reciprocal translocation for which the two species differ. One locus, Pgm-3, was detected only in C. annuum cultivars and is apparently the result of a duplication of Pgm-2 which codes for cytosolic phosphoglucomutase activity. Pgm-2 and Pgm-3 are not tightly linked (approximately 20% recombination) which supports the proposal that Pgm-3 originated from a mechanism other than unequal crossing over. A comparison of the linkage relationships of enzyme-coding genes in pepper with those of putative orthologous loci in tomato reveals that two linkage blocks, Est-1-Est-7 and Pgi-1-Est-4, may have remained intact since the divergence of Capsicum and Lycopersicon.     

The genetics of aryl hydrocarbon hydroxylase induction in mice: A single gene difference between C57BL/6J and DBA/2J

Twenty-one inbred strains of mice were surveyed for inducibility of hepatic aryl hydrocarbon hydroxylase (AHH) activity by the carcinogen 3-methylcholanthrene (MC). In 11 strains given MC, AHH activity increased 1.3- to 5-fold (inducible), whereas ten strains responded with a less than 0.5-fold increase (noninducible). Neither the inducible nor the noninducible class was homogeneous, and in each considerable variation was found in both the basal activity of AHH and the response to MC. Strains DBA/2J and C57BL/6J were chosen to represent the noninducible and inducible classes, respectively. In the crosses (C57BL/6 × DBA/2)F₁ × DBA/2 and (C57BL/6 × DBA/2)F₂, inducibility segregated as a single autosomal dominant gene. The gene symbols Ahh ⁱ and Ahh ⁿ are proposed for the alleles present in C57BL/6J and DBA/2J, respectively. No genetic linkage was found between the Ahh locus and the following loci: b, d, Es-1, Es-3, Gpd-1, Hbb, Id-1, Pgm-1, and sex. Some implications of this work in the study of mammalian enzyme induction and chemically induced carcinogenesis are discussed. There is a positive correlation between AHH inducibility and the development of an inflammatory response to the topical application of the carcinogen 7,12-dimethylbenzanthracene.     

Multigene control of Mls c

Festenstein originally described the Mls locus as a single dominant autosomal gene with four alleles which mapped in the 13th linkage group of chromosome 1. We subsequently presented evidence which indicated that the mixed leukocyte reaction stimulatory products of DBA/2 and CBA/J were controlled by two independently segregating Mls loci. Recently, Mls ^d of CBA/J was shown to be composed of Mls ^a of AKR and Mls ^c of C3H. In the present report, classic segregation data is presented which indicates that Mls ^c of C3H is controlled by three independently segregating loci. As defined by stimulatory patterns of numerous cell lines, we postulate the following: either one of the loci is shared with BALB.K, CE, C58, and partially with MA/MyJ, one is shared with CBA/H and CBA/J, and one is shared with BALB.K, CBA/J, and partially with CE; or the groups of shared determinants are controlled by different alleles of unique loci (or locus). In any event, Mls ^c appears to be composed of at least three independently segregating loci; the number of alleles/locus is being investigated. In addition, C3H was stimulated by BALB.K (both were recently postulated to be Mls ^c ); this epitope was shared with CBA/J, CBA/H, AKR/Cum, Ma/MyJ, and C58/J.     

Immune responses in vitro

The Mls locus was originally defined to have four alleles; three controlled products that were detectable in primary mixed leukocyte reactions (MLR), whereas one, b, was described as being null. Recently, other investigators postulated that the Mls locus is nonpolymorphic, being composed of the b null allele and of a singly expressed allele previously thought to be the a and d alleles. We previously reported that products controlled by Mls ^aand Mls ^dwere antigenically distinct and therefore are not controlled by the same allele, and the product of Mls ^bon cells of three different strains was easily detectable by Mls ^aand Mls ^dresponding cells. Thus the b allele is not null. In the present report evidence is presented which indicates that both Mls ^band Mls ^cencoded products were undetectable by MLR when in the presence of Mls ^aor Mls ^d. This was demonstrated by (a) the inability of Mls ^a/Mls ^cand Mls ^a/Mls ^bF₁ cells to stimulate Mls ^aresponding cells and Mls ^d/Mls ^cand Mls ^d/Mls ^bcells to stimulate Mls ^dcells; (b) the positive response of Mls ^a/Mls ^band Mls ^d/Mls ^bF₁-hybrid cells to Mls ^b-encoded products; and (c) the reactivity of Mls ^a/Mls ^cand Mls ^d/Mls ^cF₁ hybrid cells to Mls ^c-encoded determinants.