Showing papers in "Journal of Genetics in 1997"
TL;DR: It is argued that genetic release followed by diversifying evolution is made possible under a number of circumstances, and when some individuals in a species begin to rely on the indirect component of inclusive fitness while others continue to rely largely on the direct component, as workers and queens in social insects are expected to do.
Abstract: Caste polymorphism, defined as the presence within a colony of two or more morphologically differentiated individuals of the same sex, is an important character of highly eusocial insects both in the Hymenoptera (ants, bees and wasps) and in the Isoptera (termites), the only two groups in the animal kingdom where highly eusocial species occur. Frequently, caste polymorphism extends beyond mere variations in size (although the extent of variations in size can be in the extreme) and is accompanied by allometric variations in certain body parts. How such polymorphism has evolved and why, in its extreme form, it is essentially restricted to the social insects are questions of obvious interest but without satisfactory answers at the present time. I present a hypothesis entitled ‘genetic release followed by diversifying evolution’, that provides potential answers to these questions. I argue that genetic release followed by diversifying evolution is made possible under a number of circumstances. One of them I propose is when some individuals in a species begin to rely on the indirect component of inclusive fitness while others continue to rely largely on the direct component, as workers and queens in social insects are expected to do. Thus when queens begin to rely on workers for most of the foraging, nest building and brood care, and workers begin to rely increasingly on queens to lay eggs—when queen traits and worker traits do not have to be expressed in the same individual—I postulate the relaxation of stabilizing selection and new spurts of directional selection on both queen-trait genes and worker-trait genes (in contrasting directions) leading to caste polymorphism.
75 citations
TL;DR: Radiation-induced mutants of groundnut cv.
Abstract: Radiation-induced mutants of groundnut cv. Spanish Improved showing distinct morphological differences and the parent were screened for RAPD variability. The analysis revealed characteristic band differences among the 12 mutants and the parent. The polymorphic RAPD bands were dominant in the F1 and segregated in a Mendelian fashion in the F2. The RAPD technique brought out greater genome variability than RFLP.
31 citations
TL;DR: These analyses showed that in each of these countries, local cat populations have characteristic genetic profiles which were different to neighbouring populations in nearby countries.
Abstract: The allelic frequencies of nine Mendelizing genetic characteristics that control coat colour, tabby and length and some skeletal abnormalities have been studied in four feral domestic cat populations, two in the north of Catalonia (Girona and Roses & L’Estartit, northeastern Spain) and two Adriatic Italian populations (Rimini and Venice). Using different genetic and multivariate analyses (Nei’s and Cavalli-Sforza and Edwards’s genetic distances, phenograms and cladograms using different algorithms, strict consensus trees, canonical population, principal coordinates and nonmetric multidimensional scaling analyses), I show the genetic relationships between these populations and other Western European cat populations previously studied. In the Western European area comprising Catalonia, Italy, France and Great Britain, I found significant spatial structure for thetb, l andW alleles and for the average correlogram for the seven alleles studied as a whole using a spatial autocorrelation analysis. The genetic distance matrices between these European cat populations also showed a significant correlation with the geographical distance between these populations using Mantel’s test. These analyses showed that in each of these countries, local cat populations have characteristic genetic profiles which were different to neighbouring populations in nearby countries. At least in this area of Western Europe, the geographical distances between cat populations (although the gene flow can be relatively high) is an important factor which can explain differences in allele frequencies between these populations.
28 citations
TL;DR: This review is an attempt to examine some of the well-characterized cryptic genetic systems in Escherichia coli in an effort to understand their functional and evolutionary significance.
Abstract: Many microorganisms carry genes that have the potential to code for specific functions but remain inactive during the normal lifetime of the organism. Such genes have been termed cryptic genes and their activation usually requires a mutational event. They are different from pseudogenes which arise as a result of duplication of a functional gene but remain inactivated because of the accumulation of multiple mutations. This review is an attempt to examine some of the well-characterized cryptic genetic systems in Escherichia coli in an effort to understand their functional and evolutionary significance.
22 citations
TL;DR: The genetic structure of natural populations of the domestic cat was examined using frequency data for seven monogenic morphological traits and there was no evidence for nonrandom mating within colonies, and estimates of between-colony gene flow were quite high.
Abstract: The genetic structure of natural populations of the domestic cat was examined at the microgeographic level (in the Spanish city of Barcelona) and the macrogeographic level (in Catalonia in Spain, and in upper midwestern USA) using frequency data for seven monogenic morphological traits. At the microgeographic level in the city of Barcelona there was no evidence for nonrandom mating within colonies, and estimates of between-colony gene flow were quite high. At the macrogeographic level, the populations from Catalonia and upper midwestern USA differed in two major respects: (i) The Catalan populations were in reasonably good agreement with expectations of Hardy-Weinberg equilibrium while the North American populations showed some evidence of the Wahlund effect (overall heterozygote deficiency indicating population substructuring). (ii) In the Catalan populations, approximately fifty per cent of the genetic differentiation between populations could be explained by geographical separation while in North America only four per cent of the total differentiation was attributable to geographical distance.
17 citations
TL;DR: Three population samples of Sinipta dalmani polymorphic for the M4 inversion were analysed for five body-size-related traits: total body, tegmina, third femur, third tibia and thorax lengths, suggesting that the differences between karyomorphs are largely additive.
Abstract: Three population samples ofSinipta dalmani from Entre Rios Province in Argentina polymorphic for the M4 inversion were analysed for five body-size-related traits: total body, tegmina, third femur, third tibia and thorax lengths. MANOVA and individual ANOVA revealed that there were significant differences between karyomorphs for total body and thorax lengths. The univariate analyses also revealed significant differences for tibia length, showing an important influence of correlated traits. The influence of the M4 inversion leads to a significant reduction of body size in the homozygotes for the M4 inversion. Comparison of mean values for tibia length through Scheffe’s method revealed that (i) heterozygotes were intermediate between homozygotes, and (ii) there were significant differences between homozygotes. These results suggest that the differences between karyomorphs are largely additive. On the contrary, the heterozygote mean value for thorax length differs significantly from the average of the two homozygotes, showing that the dominance effects are mainly related with the differences between karyomorphs. This parametric comparison using total body length data revealed only marginally significant differences. Regression analysis of morphological traits on number of inverted chromosomes revealed that there was a dose effect only for third tibia length.
16 citations
TL;DR: Values corroborate that the pygmy field and house mice are closely allied and show an unusually high genetic variation in the field mice.
Abstract: Genetic variation in the Indian pygmy field miceMus booduga and theMus terricolor complex and in the house mouseMus musculus tytleri was analysed electro phoretically at 20 enzymatic and nonenzymatic protein loci. The results show an unusually high genetic variation in the field mice in terms of per cent polymorphism (P = 75 to 90 at 0-95 level), observed heterozygosity (Ho = 0.215[ ± 0.213] to 0.314 [±0.236]) and average number of alleles(A = 2.0[± 0.858] to 2.38 [±0.868]). Very high values of P,Ho andA were also observed for the house mouse. Genetic distance (D) determined by using Nei’s (1978) formula in theM. terricolor complex ranged from the lowest,D = 0.082, betweenM. terricolor I and II to the highest,D = 0.155, betweenM. terricolor II and III. Genetic distance betweenM. booduga and theM. terricolor complex was 0-259 and that between the house mouseM. m. tytleri and theM. booduga-terricolor lineage was 0.285. TheseD values corroborate that the pygmy field and house mice are closely allied.
7 citations
TL;DR: Escherichia coli MD1157, a routine isolate of AB1157 maintained in the authors' laboratory, was noticed to have spontaneously acquired two conditional cold-dependent phenotypes: Cs (cold sensitivity) and Smsc (streptomycin sensitivity in cold).
Abstract: Escherichia coli MD1157, a routine isolate of AB1157 maintained in our laboratory, was noticed to have spontaneously acquired two conditional cold-dependent phenotypes: Cs (cold sensitivity) and Smsc (streptomycin sensitivity in cold). Cs involved delayed appearance of visible colonies on solid (LB or minimal) medium in cold (22° C or below) without any loss of viability, and an extended lag period and longer doubling time following a temperature downshift in liquid medium. Smsc involved conditional suppression of therpsL31 -mediated streptomycin (Sm) resistance in cold, resulting in reduced colony forming ability in the presence of Sm. This phenotype was seen only on LB plates and weakly on minimal-medium plates containing some LB, but not on minimal medium alone. Genetic mapping traced these two phenotypes to mutations in two genes mapping to the 14-15 min region of the standardE. coli map, which have been namedgicA (growth in cold) andgicB respectively. Comparison of MD1157 with transductants which had lost either one or both of these mutations showed that whilegicBl contributes only to Smsc,gicAl is associated with both Cs and Smsc. Comparison of these strains with AB1157 suggested the involvement of a third, as yet unidentified gene in causing these phenotypes.
7 citations
TL;DR: Northern hybridization data indicated that all four genes ofpsbE-F-L-J operon were transcribed as a single tetracistronic message which was not subjected to further processing into smaller transcripts.
Abstract: A 5-5-kbpHindIII fragment carryingpsbE-F-L-J operon from the chloroplast DNA ofPopulus deltoides was cloned and nucleotide sequence was determined for a 1672-bp region. The coding regions showed more than 90% homology at nucleotide sequence level with plastid-encodedpsbE, psbF, psbL andpsbJ genes of higher plants. Pairwise alignments ofpsbE, psbF, psbL andpsbJ coding regions of poplar with published sequences from other plants were carried out to analyse the nature of nucleotide substitutions. The 5’ and 3’ untranslated regions of the genes revealed high variability among different organisms both in terms of homology and the number of nucleotides. Northern hybridization data indicated that all four genes ofpsbE-F-L-J operon were transcribed as a single tetracistronic message which was not subjected to further processing into smaller transcripts. The transcript showed quantitative increase in mature leaves.
6 citations
TL;DR: It is found that allele frequency data on about 30 microsatellite loci and the use ofDA (Neiet al. 1983) orDc (Cavalli-Sforza and Edwards 1967) distance measures with UPGMA clustering algorithm can recover true short-term evolutionary relationships with a high degree of accuracy, unless the effective sizes of the populations or mutation rates or both are very small.
Abstract: Because microsatellite loci are abundant in the human genome and are highly polymorphic in most global populations, such loci have become very popular in studies on reconstructing evolutionary relationships among contemporary human populations. We have made an assessment of the efficiency of recovery of true evolutionary relationships using simulated data of microsatellite loci and a variety of distance measures. We find that allele frequency data on about 30 microsatellite loci and the use ofD
A (Neiet al. 1983) orD
c (Cavalli-Sforza and Edwards 1967) distance measures with UPGMA clustering algorithm can recover true short-term evolutionary relationships with a high degree of accuracy, unless the effective sizes of the populations or mutation rates or both are very small.
5 citations
TL;DR: A study of the geographical organization of allozyme diversity over a wider range of the distribution of D. elongatus suggests that causes other than drift and migration may explain the observed directional patterns of variation in the grasshopper population.
Abstract: Previous studies on allozyme variation in five populations of the grasshopperDichroplus elongatus along a geographical gradient in Argentina revealed a significant degree of population structuring and a significant association between one of the loci (Aat-1) and latitude. As this could not be entirely explained by historical factors, the possible adaptive significance of this locus or loci in linkage disequilibrium was investigated in the present study, with an emphasis on the role of environmental variables correlated with latitude. The present paper reports a study of the geographical organization of allozyme diversity over a wider range of the distribution ofD. elongatus. The relation of allelic frequencies with geographic climatic variables was analysed. We have found (i) that different loci (Aat-1 andPep-1) covary significantly with different variables, (ii) discordance between genetic and geographical distances, (iii) copious gene flow that would mask allelic frequency differences due solely to genetic drift, (iv) and temporal stability of the gradient found. The results suggest that causes other than drift and migration may explain the observed directional patterns of variation inD. elongatus.
TL;DR: A matrix model is considered to describe the population dynamics of the Indian paper wasp waspRopalidia marginata and the stable class distribution of this model is obtained and applied to compute the worker-brood genetic relatedness of the colony.
Abstract: We consider a matrix model to describe the population dynamics of the Indian paper waspRopalidia marginata, a eusocial insect species of peninsular India. We obtain the stable class distribution of this model and apply it to compute the worker-brood genetic relatedness of the colony. Our results are compared with those obtained by observational studies. Further, we study the effect of changes in turnover rates and survival rates on the genetic relatedness coefficient with the help of the theoretical formulae.
TL;DR: Evidence suggestive of positive selection acting on certain regions of the E gene of the Japanese encephalitis virus, and in some cases on the entire gene, was obtained.
Abstract: The variation in nucleotide sequence observed in the envelope (E) gene and the prM (precursor of M protein) region of different strains of Japanese encephalitis virus (JEV) was analysed. Presence of selective forces acting on these regions was investigated by computing the relative rates of synonymous (K
s) and nonsynonymous (K
a) substitutions. The ratioK
s/K
a was used as an indicator of the overall selective constraints on the amino acid sequence of JEV proteins. The possibility that different regions of the gene may be subject to varying selective pressures was tested by dividing the gene into three regions and estimating theK
s/K
a ratio for each region. On the basis of analysis of a limited number (17) of strains of JEV, evidence suggestive of positive selection acting on certain regions of the E gene of the virus, and in some cases on the entire gene, was obtained. Analysis ofK
a diversity in the prM region of 46 JEV strains grouped into three genotypes revealed that strains included in genotype II were more heterogeneous than strains belonging to genotype I, while the differences between meanK
a values for genotypes I and III and genotypes II and III were not statistically significant. Analysis of host-specific heterogeneity in the prM region revealed that pig isolates were more Xa-diverse than human isolates.
TL;DR: The chromosome ofAzotobacter vinelandii was digested with the restriction endonucleasesSpeI, DraI, and Asel and the products were separated by pulsed-field gel electrophoresis to determine whether there are multiple identical chromosomes in A. v inelandii or one large chromosome with identical segments joined in tandem.
Abstract: The chromosome ofAzotobacter vinelandii was digested with the restriction endonucleasesSpeI (5’-ACTAGT),DraI (5’-TTTAAA) andAsel (5’-ATTAAT) and the products were separated by pulsed-field gel electrophoresis. The sum of the sizes of the restriction fragments comes to around 4.5 megabasepairs. Our earlier studies had revealed the presence of about 80 copies ofnifH, nifD, nifK andleuB genes in a log-phase cell ofA. vinelandii. To determine whether there are multiple identical chromosomes inA. vinelandii or one large chromosome with identical segments joined in tandem, we have subjected gamma-irradiated DNA ofA. vinelandii andEscherichia coli to pulsed-field gel electrophoresis. The results suggest thatA. vinelandii chromosomes contain multiple identical chromosomes of about the same size as that ofE. coli.
TL;DR: The results suggest an indirect role of the cytoskeletal protein encoded by Igl tumour suppressor gene in aspects of normal chromosome condensation during mitosis.
Abstract: Homozygosity for recessive mutations inDrosophila tumour suppressor genes likelethal giant larvae (Igl), lethal giant discs (Igd) orfat (ft) induce uncontrolled cell proliferations in the imaginal discs of the mutant larvae. Imaginal discs of larvae mutant forIgl tumour suppressor gene display neoplastic growths while those mutant forIgd orfat display hyperplastic growths. Results presented in this study reveal that mutant wing imaginal discs with neoplastic or hyperplastic overgrowths display high mitotic activity primarily during the extended period of larval life when their wild-type siblings have already pupariated. Both these categories of overgrowths show overall stability of the karyotypes and only low frequency of aneuploidy. The hyperplastic imaginal discs ofIgd orft mutant larvae displayed normal chromosome condensation. In contrast, the neoplastic imaginal discs ofIgl mutants showed high frequency of mitotic cells with undercondensed chromosomes. In this respect the neoplastic discs resemble malignant neuroblastomas of theIgl larvae which also display undercondensed chromosomes. These results thus suggest an indirect role of the cytoskeletal protein encoded byIgl tumour suppressor gene in aspects of normal chromosome condensation during mitosis.
TL;DR: A set of 340 P insert lines on the X chromosome and the autosomes were screened for altered responses of the labellar chemoreceptors to salts and sucrose, defining a new gene that affects Na+ response of the fly.
Abstract: A set of 340 P insert lines on the X chromosome and the autosomes were screened for altered responses of the labellar chemoreceptors to salts and sucrose. A mutant linegustJ was isolated in which the electrophysiological response of the salt-sensitive neuron to Na+ in the sensilla of the proboscis is reduced. The responses to KC1 and sucrose are unaffected. In feeding tests,gustJ flies have Na+-specific defects. Heterozygotes ofgustJ with two other salt mutantsgustE andBE1323 are normal. Multiple alleles ofgustJ have been obtained by excision of the original P element. All mutants have defects in Na+ sensing specifically, thus defining a new gene that affects Na+ response of the fly.