Localization of the Po2 locus in the S, Phi, Hal, H, Po2, Pgd linkage group in pigs

The localization of the Po2 locus controlling a polymorphic serum postalbumin was studied in 41 families of the Czech Landrace breed. The haplotypes involving six closely linked loci (S, Phi, Hal, H, Po2, Pgd) were determined for each family member. The crossovers observed between the H, Po2 and Pgd loci indicated that Po2 is located between H and Pgd. The Po2 locus appears to be closer to H [theta = 0.54% (0.06%-1.92%)] than to Pgd [theta = 4.02% (1.67%-7.96%)]. A strong Ha-Po2S association (r = 0.96, P less than 0.001) and H-PO2 linkage disequilibrium (D = 0.2218, P less than 0.01, D/DMax = 0.98) were found.     

Polymorphisms, Linkage and Mapping of Four Enzyme Loci in the Fish Genus Xiphophorus (Poeciliidae)

Electrophoretic variants at four additional enzyme loci--two esterases (Est-2, Est-3), retinal lactate dehydrogenase (LDH-1) and mannose phosphate isomerase (MPI)--among three species and four subspecies of fish of the genus Xiphophorus were observed. Electrophoretic patterns in F1 hybrid heterozygotes confirmed the monomeric structures of MPI and the esterase and the tetrametric structure of LDH in these fishes. Variant alleles of all four loci displayed normal Mendelian segregation in backcross and F2 hybrids. Recombination data from backcross hybrids mapped with Haldane's mapping function indicate the four loci to be linked as Est-2--0.43--Est3--0.26--LDH-1--0.19--MPI. Significant interference was detected and apparently concentrated in the Est-3 to MPI region. No significant sex-specific differences in recombination were observed. This group (designated linkage group II) was shown to assort independently from the three loci of linkage group I (adenosine deaminase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase) and from glyceraldehyde-3-phosphate dehydrogenase and two isocitrate dehydrogenase loci. Evidence for conservation of the linkage group, at least in part, in other vertebrate species is presented.     

6-phosphogluconate dehydrogenase in the housefly,Musca domestica L.: Evidence for inheritable 6PGD polymorphism

Two electrophoretic variants of the 6-phosphogluconate dehydrogenase (6 PGD) enzyme have been found in the WHO/IN/Musca domestica/l housefly laboratory strain. The patterns shown by Cellogel zone electrophoresis can be fully explained by the hypothesis of two codominant autosomal alleles. On this hypothesis, a specific Pgd locus has been postulated and the symbols PgdA and PgdB have been assigned to the two alleles causing the PGD-A and PGD-B phenotypes. The bands corresponding to the homozygous phenotypes PGD-A and PGD-B have different electrophoretic mobility and staining intensity; they can be described, respectively, as "fast-weak" and "slow-thick." The heterozygous phenotype PGD-AB gives a three-banded pattern, indicative of a dimeric structure for this enzyme; this pattern is asymmetrical. Heterozygous flies have been found both among wild-type strains of recent colonization and among old established laboratory colonies. Most strains are PgdB monomorphic; up to now only three strains have been PgdA monomorphic, all of them being multimarker strains. The Pgd locus has been traced to the housefly linkage group III.     

Biochemical markers in rats: Linkage relationships of aconitase (Acon-1), aldehyde dehydrogenases (Ahd-2 and Ahd-c), alkaline phosphatase (Akp-1), and hydroxyacid oxidase (Hao-1)

We have examined the linkage relationships between five biochemical markers, Acon-1, Ahd-2, Ahd-c, Akp-1, and Hao-1, and 19 other genetic loci in five breeding combinations. The genetic locus that codes for a recently described aldehyde dehydrogenase in the liver (Ahd-c) has been assigned to linkage group X (LG X). Hydroxyacid oxidase is coded for by a locus (Hao-1) that is linked to genes that encode agouti coat color and seminal vesicle proteins in linkage group IV. Alkaline phosphatase (Akp-1) was linked to the locus that encodes the C6 component of complement and this association provisionally defines a new linkage group (LG XI) in the rat. The locus Acon-1 could not be positively assigned to a specific linkage group but the results from one breeding combination suggest that this locus may be included in linkage group II. No linkage relationship could be detected for the aldehyde dehydrogenase coded for by Ahd-2.This work was supported by Grant GM 32580 from the National Institutes of Health, United States Public Health Service.     

Linkage relationships of seven enzyme and two pigmentation loci in the snail Biomphalaria glabrata

Crossing experiments with inbred stocks of the snail (Biomphalaria glabrata) demonstrated that variants at two loci determining pigmentation and seven enzyme-determining loci exhibited normal Mendelian segregation ratios in F2 progeny. Among 39 pairwise comparisons for joint segregation, there was evidence of genetic linkage between a locus controlling mantle pigmentation (S) and 6-phosphogluconate dehydrogenase (Pgd) and confirmation of a previously described linkage between esterase-2 (Est-2) and catalase (Cat). Recombination fractions were estimated to be 17 +/- 4 for S-Pgd and 33 +/- 5 for Est-2-Cat. The remaining five loci--Acon-1, Pgm-1, Lap-1, Lap-2, and Pgd--assorted independently. This brings to 17 the number of loci examined for segregation and assortment in this medically important species. As Biomphalaria has a chromosome number n = 18, markers should soon be available for most or all of the linkage groups.     

Linkage studies in blood biochemical polymorphic markers of rabbits

Five erythrocyte proteins (Adenosine deaminase, Ada; 6-Phosphogluconate dehydrogenase, Pgd; Esterase 1, Es-1; Esterase 3, Es-3; NADH-Diaphorase 2, Dia-2) and a serum beta-globulin protein (Esterase 7, Est-7) were studied in rabbits using starch gel electrophoresis. Samples were obtained from 317 Spanish Common individuals (38 families, 317 individuals). For the analyses of linkage, Morton's sequential probability ratio test was applied. Clear evidence for linkage between Es-1 and Est-7 (theta 0.2) was obtained, and no evidence of linkage was obtained for the remaining pairwise combinations of loci studied.     

Genetic variation at a pig serum protein locus, Po-2 and its assignment to the Phi, Hal, S, H, Pgd linkage group

Two-dimensional agarose gel (pH 5.4)-polyacrylamide gel (pH 9.0) electrophoresis of pig serum samples revealed a new serum protein (postalbumin-2, PO-2) polymorphism. Family data supported the hypothesis that the three PO-2 phenotypes observed were controlled by two codominant, autosomal alleles (Po-2F and Po-2s) at a single locus. The frequency of Po-2F in Swedish Landrace and in Swedish Yorkshire breeds was estimated at 0.74 and 0.65, respectively. Evidence was presented for close genetic linkage between Po-2 and the red cell phosphohexose isomerase locus (Phi). A recombination frequency of 3.2% was obtained from double backcross material. Data obtained in a Danish Landrace material showing linkage between the Po-2 locus and the H blood group locus, the Pgd locus and Hal (locus for halothane sensitivity) are also given. A total of seven recombinants were observed. They show that Po-2 is a new locus in a previously established linkage group. The likely sequence of the loci is: Phi, Hal, S, H, Po-2, Pgd.     

Polymorphism in Pg-1 (urinary pepsinogen-1) locus in the rat and its linkage analysis

Cramer (1981) reported that Pg-1 (urinary pepsinogen) in the rat was loosely linked with albinism in the linkage group I. We performed a three point test on the loci of pg-1, c, and Hbb. We could reconfirm that pg-1 was autosomal trait with two co-dominant alleles of pg-1a and pg-1b. But in progeny of ((WF X IS) X WF) backcross, pg-1 was linked to neither c nor Hbb, while a close linkage between c and Hbb was detected. Also pg-1 was not linked to Mup-1 (LG II), a (LG IV), Es-3 (LG V), and h (LG VI). pg-1 will be one of the most valuable genetic markers of the rats, since pg-1 was highly polymorphic among inbred strains of rats, and not linked to LG I, II, IV, V, and VI.     

The position of the epistatic S locus in the halothane linkage group in pigs

The linkage of the Phi, Pgd, Po2, S, H and halothane sensitivity loci was followed in a Belgian Landrace family, heterozygous for these systems over 6 generations. Recombination next to the S locus occurred mainly in pigs belonging to this particular family. From this investigation the position of the S locus is proved to be outwith the Phi-Pgd region, next to Phi. Therefore the gene sequence S - Phi - Hal - H - Po2 - Pgd is proposed. Higher recombination rates were observed in the female parental line of the multiheterozygous family when compared to the male parental line. Additional data from animals, unrelated to this strain, confirm the evidence of close linkage of the S system to the nearest marker loci.     

Linkage relationships of six enzyme Loci in interspecific sunfish hybrids (genus lepomis)

Backcross hybrids produced from the bluegill, the red-ear sunfish, and their F₁ interspecific hybrid have been analyzed for the inheritance of six enzyme phenotypes. Malate dehydrogenase A and B, tetrazolium oxidase, 6-phosphogluconate dehydrogenase, skeletal muscle esterase, and liver α-glycerophosphate dehydrogenase are all inherited in a mendelian manner as codominant alleles at nuclear loci. 6-phosphogluconate dehydrogenase and α-glycerophosphate dehydrogenase are encoded by linked loci, undergoing recombination at a frequency of 15%-22%. No other case of linkage was observed. The absence of linkage between the homologous malate dehydrogenase loci is of particular interest. These interspecific hybrids appear to be very useful for studies of biochemical genetics.     

A new allele at the Pgd locus in pigs

A new electrophoretic variant of porcine 6-phosphogluconate dehydrogenase (PGD) is described. The new variant, PGD C, has been shown to be controlled by a third allele, PgdC, at the Pgd locus.     

Genetic variation at a pig serum protein locus, Po-2 and its assignment to the Phi, Hal, S, H, Pgd linkage group

Two-dimensional agarose gel (pH 5.4)-polyacrylamide gel (pH 9.0) electropho-resis of pig serum samples revealed a new serum protein (postalbumin-2, PO-2) polymorphism. Family data supported the hypothesis that the three PO-2 phenotypes observed were controlled by two codominant, autosomal alleles ( Po-2^F and Po-2^S ) at a single locus. The frequency of Po-2^F in Swedish Landrace and in Swedish Yorkshire breeds was estimated at 0.74 and 0.65, respectively. Evidence was presented for close genetic linkage between Po-2 and the red cell phospho-hexose isomerase locus ( Phi ). A recombination frequency of 3.2 % was obtained from double backcross material. Data obtained in a Danish Landrace material showing linkage between the Po-2 locus and the H blood group locus, the Pgd locus and Hal (locus for halothane sensitivity) are also given. A total of seven re-combinants were observed. They show that Po-2 is a new locus in a previously established linkage group. The likely sequence of the loci is: Phi, Hal, S, H, Po-2, Pgd .     

Gene order and recombination rates in the linkage group S-Phi-Hal-H-(Po2)-Pgd in pigs

Families of Czech Landrace (94 litters and 636 offspring) were tested for halothane sensitivity, A-O (S), H, PHI and PGD phenotypes. Informative matings for the estimation of recombination rates between marker loci were selected. The following recombination frequencies were established: S - Phi = 4.8% (2.5%-10.7%); S - H = 6.8% (4.3%-11.7%); Phi - H = 2.6% (0.9%-5.3%); H - Pgd = 4.4% (1.6%-8.0%). Cross-overs were observed also between S - Hal, Hal - H and Hal - Pgd, but were not found between Phi - Hal. On the basis of these results it has been possible to revise the position of the S locus in this linkage group. The most probable gene order would be: S - Phi - Hal (or Hal - Phi) - H - (Po2) - Pgd. A striking difference was found between the number of halothane-sensitive pigs (87) and HalnHaln genotypes determined by haplotyping (123). Segregation rates in 19 backcross matings and experimental matings of the animals proved that this difference is mostly due to incomplete penetrance or low expression of halothane sensitivity.     

Purification and characterization of cytosolic 6-phosphogluconate dehydrogenase isozymes from maize

Cytosolic isozymes of 6-phosphogluconate dehydrogenase were purified from roots of maize (Zea mays L.). The final preparation contained two 55-kD proteins. Affinity-purified dehydrogenases from a maize line that is null for both cytosolic 6-phosphogluconate dehydrogenase isozymes (Pgd1-null, Pgd2-null) lacked the 55-kD proteins. The substrate kinetics of the purified enzyme were determined.     

Variations in the expression of the gene Pgd due to the effect of chromosomal rearrangements in Drosophila melanogaster

The effects of chromosomal rearrangements on the expression of the gene Pgd coding for 6-phosphogluconate dehydrogenase (PGD) was studied in D. melanogaster. Of 21 chromosomal rearrangements examined, 2 produced complete loss of PGD activity, 10 markedly decreased it, 3 slightly increased it, and 6 had no appreciable effect. The effect of some rearrangements can be restricted to the larval stage. The results of histochemical staining and the quantitative analysis of the electrophoretic PGD patterns allowed us to identify chromosomal rearrangements whose inhibition of PGD activity was due to mosaic expression of the Pgd gene. The rearrangements whose effects are variegated represented 50% of those decreasing the expression of the marker gene or about 25% of those we considered.     

Correlation of axenic linkage groups with the position of the microtubule-organizing center in aggregating Dictyostelium.

Positioning of the microtubule-organizing center (MTOC) in Dictyostelium discoideum was found to be genetically regulated. We examined the wild-type strain NC-4 cells independently maintained in different laboratories, freshly recovered cells from spores stocked for over 20 years, the temperature-sensitive growth mutant HU49 isolated from NC-4, as well as strain V-12 which is the opposite mating-type to NC-4. During aggregation on nonnutrient agar plates, all these strains showed similar cell polarity, as defined by the alignment of the nucleus ahead of the MTOC. By contrast, in Ax2 and Ax3, axenic strains carrying axenic mutations on linkage groups II and III, the MTOC was usually positioned ahead of the nucleus. Cells containing axenic linkage group II but not III positioned the MTOC ahead of the nucleus. Conversely cell polarity of strains including axenic linkage group III but not II was similar to that of wild-type cells. Thus axenic linkage group II, probably axeC or other linked gene(s) not yet identified, is responsible for the location of the MTOC anterior to the nucleus during aggregation. The anterior positioning of the MTOCs was prevented by growth on bacteria in cells carrying both axenic linkage groups, but not in those carrying only axenic linkage group II.     

Location of genes on chromosome arms in the Anopheles gambiae group of species and their correlation to linkage data for other anopheline mosquitoes

The use of paracentric inversions as genetic markers in the Anopheles gambiae group of mosquitoes is described. The gene for dieldrin resistance is assigned to chromosome 2 which in turn is correlated to the previous assignment of the gene to linkage group II. The locus of the enzyme phosphoglucomutase 2 (Pgm 2) is similarly assigned to chromosome 2 and evidence is presented for possible linkage between Pgm 2 and dieldrin resistance. There was no linkage or correlation of chromosome 2 and loci of the enzymes superoxide dismutase (Sod) and octanol dehydrogenase (Odh). These genes are therefore assumed to be on chromosome 3 (linkage group III). Evidence that such gene linkage group/chromosome correlations may extend to other species for which chromosome maps and homologies have been worked out is discussed.     

Geographical distribution of isozyme alleles for phosphogluconate dehydrogenase in barley.

The Ak and Tj alleles at the Pgd1 locus and the Ps and Tn alleles at the Pgd2 locus were detected for phosphogluconate dehydrogenase in barley. The Ak allele at the Pgd1 locus was widely distributed around the world, while the Tj allele was found only in two accessions from Nepal and one from India. At the Pgd2 locus, the Ps allele was abundant everywhere, whereas the Tn allele was occasionally found in Caucasus, Turkey, and Europe, and scarcely or none in Korea, China, Nepal, India, and Ethiopia. The Tn allele was also detected in Japanese accessions. Among them, six-rowed varieties carrying the Tn allele were principally grown in northern parts of Japan and characterized by covered kernel, the Occidental type for nonbrittleness of rachis, and resistance to Japanese races of powdery mildew. However, the loci responsible for these characteristics were independent of the Pgd1 locus.     

Assignment of 6-phosphogluconate dehydrogenase and malate dehydrogenase to chromosome 3 ofAnopheles stephensi

Genetics and linkage analysis of 6-phosphogluconate dehydrogenase (6-PGD) and malate dehydrogenase (MDH) have been investigated in Anopheles stephensi. Both these markers were found to be autosomal and linked and have been assigned to linkage group III. Two mutant markers, Black larva (Bl) and golden-yellow larva (gy), were used to establish the map distances, and the current sequence of loci on chromosome 3 is as follows: Bl (3.75)-gy (14.53)-Mdh-2 (49.83)-6-pgd.     

6-Phosphogluconate dehydrogenase (PGD) genetics in the mouse: Linkage with metabolically related enzyme loci

An electrophoretic polymorphism of 6-phosphogluconate dehydrogenase (PGD) has been observed in the subspecies Mus musculus musculus from northern Denmark. M. m. musculus is interfertile with inbred strains of mice, and F1 hybrids with C57BL/6J show a three-banded phenotype. This pattern is consistent with a dimeric enzyme structure with codominant expression of alleles. In backcrosses and the F2 generation, PGD segregated as a singly autosomal gene, designated Pgd, closely linked to Gpd-1 on chromosome 4(1.7 +/- 1.1%). Both gene products are dimers, both require NADP, and these enzymes catalyze sequential steps in metabolism.