Alternative Alleles (alternative + allele)

Distribution by Scientific Domains


Selected Abstracts


Is natural selection a plausible explanation for the distribution of Idh- 1 alleles in the cricket Allonemobius socius?

ECOLOGICAL ENTOMOLOGY, Issue 1 2006
Diana L. Huestis
Abstract., 1.,Allozyme alleles in natural populations have been proposed as either neutral markers of genetic diversity or the product of natural selection on enzyme function, as amino acid substitutions that change electrophoretic mobility may also alter enzyme performance. To address these possibilities, researchers have used both correlative analyses and empirical studies. 2.,Here, geographically structured variation of the enzyme isocitrate dehydrogenase (Idh- 1) in the striped ground cricket Allonemobius socius Scudder (Orthoptera: Gryllidae) is examined. The distributions of Idh- 1 alleles appear to be related to environmental gradients, as allele frequencies showed significant relationships with mean annual temperature and precipitation. Specifically, the slowest mobility allele was more frequent at colder temperatures, while the converse occurred for the fastest mobility allele. 3.,An exploratory experiment was performed to examine fitness effects of possessing different Idh- 1 alleles at two temperatures to test the hypothesis that the geographic structure of this locus may reflect environmental adaptation. Results showed that a significant interaction between temperature and Idh- 1 genotype affected the number of eggs laid, with success of homozygous individuals matching environmental expectations. 4.,The above results show that (1) variation in the frequency of Idh- 1 alleles is significantly related to environmental gradients in the eastern U.S.A. and (2) alternative alleles of Idh- 1 appear to influence the egg-laying ability of individuals differently depending on environmental temperature. Together, these results suggest that natural selection is a plausible mechanism underlying the distribution of Idh- 1 alleles in this species, although more detailed studies are needed. [source]


Extensive HLA class I allele promiscuity among viral CTL epitopes

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2007
Nicole Frahm
Abstract Promiscuous binding of T helper epitopes to MHC class II molecules has been well established, but few examples of promiscuous class I-restricted epitopes exist. To address the extent of promiscuity of HLA class I peptides, responses to 242 well-defined viral epitopes were tested in 100 subjects regardless of the individuals' HLA type. Surprisingly, half of all detected responses were seen in the absence of the originally reported restricting HLA class I allele, and only 3% of epitopes were recognized exclusively in the presence of their original allele. Functional assays confirmed the frequent recognition of HLA class I-restricted T cell epitopes on several alternative alleles across HLA class I supertypes and encoded on different class I loci. These data have significant implications for the understanding of MHC class I-restricted antigen presentation and vaccine development. [source]


The cholecystokinin type A receptor g.179A>G polymorphism affects feeding rate

ANIMAL GENETICS, Issue 2 2008
R. D. Houston
Summary A polymorphism within the 5, untranslated region of the cholecystokinin type A receptor (CCKAR) gene has been shown to affect feed intake and growth in commercial pig lines. To further investigate the phenotype of animals carrying alternative alleles at this polymorphism, we genotyped animals from a distinct segregating commercial line and an experimental cross F2 population, both with electronically recorded feeding pattern data. The data indicate that the daily feed intake increasing effect of the DQ496228:g.179G allele is mediated through a faster rate of feed intake, without evidence for an effect on other feeding behaviour traits. [source]


Genetic characterization of naturalized populations of brown trout Salmo trutta L. in southern Chile using allozyme and microsatellite markers

AQUACULTURE RESEARCH, Issue 7 2003
N Colihueque
Abstract This study describes the genetic structure of five naturalized populations of brown trout in southern Chile using allozyme and microsatellite markers to establish levels of intra- and interpopulation genetic variability and divergence. Fourteen enzymatic systems were used comprising 20 loci and three microsatellite loci specific to brown trout. The genetic variability values (allozymes, P=20,35%, average=27%, HO=0.118,0.160, average=0.141; microsatellites, P=33.3,100%, average=66.66%, HO=0.202,0.274, average=0.229) are similar to values described in other naturalized populations of brown trout present in Chile, but higher than those observed in European populations of this species. Values of total genetic diversity (HT) (allozymes=0.1216 and microsatellites=0.3504) and relative genetic divergence (GST) (allozymes=9.5% and microsatellites=15%) were also similar to the results obtained in previous studies of Chilean populations of brown trout. These values, when compared with those obtained in Europe, proved to be similar for HT but lower for GST. The low interpopulational genetic differentiation was in accordance with the small genetic distance observed between the populations analysed (D Nei=0.004,0.025). On the other hand, the high frequency of one of the two alternative alleles of the phylogeographic marker locus LDH-5* in the populations analysed (LDH-5*90>0.84) would indicate a European origin, in particular Atlantic as opposed to Mediterranean, for the brown trout introduced into Chile. The high levels of genetic variability suggest a mixed origin for the naturalized brown trout in Chile, which could have originated either before or during the introduction process. Nevertheless, the low level of genetic differentiation between populations could reflect the short lapse of time in evolutionary terms, during which populations introduced into Chile have been exposed to different evolutionary forces, and which has not been sufficiently long to produce greater genetic differentiation between populations. [source]


The evolution of alternative morphs: density-dependent determination of larval colour dimorphism in a butterfly

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009
KARL GOTTHARD
Understanding the ultimate causes for the presence of polymorphisms within populations requires knowledge of how the expression of discrete morphs is regulated. In the present study, we explored the determination mechanism of a colour dimorphism in larvae of the butterfly Pararge xiphia (Satyrinae: Nymphalidae) with the ultimate aim of understanding its potential adaptive value. Last-instar larvae of P. xiphia develop into either a green or a brown morph, although all individuals are invariably green during the preceding three instars. A series of laboratory experiments reveal that morph development is strongly environmentally dependent and not the result of alternative alleles at one locus. Photoperiod, temperature, and in particular larval density, all influenced morph determination. The strong effect of a high larval density in inducing the brown morph parallels other known cases of density-dependent melanization in Lepidopteran larvae. Because melanization is often correlated with increased immune function, this type of determination mechanism is expected to be adaptive. However, the ecology and behaviour of P. xiphia larvae suggests that increased camouflage under high-density conditions may be an additional adaptive explanation. We conclude that the colour dimorphism of P. xiphia larvae is determined by a developmental threshold that is influenced both by heredity and by environmental conditions, and that selection for increased immune function and camouflage under high-density conditions may be responsible for maintaining the dimorphism. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 256,266. [source]