scholarly journals Genetic analysis of phenotype in Trypanosoma brucei : a classical approach to potentially complex traits

2002 ◽  
Vol 357 (1417) ◽  
pp. 89-99 ◽  
Author(s):  
Andy Tait ◽  
Dan Masiga ◽  
Johnstone Ouma ◽  
Annette MacLeod ◽  
Juergen Sasse ◽  
...  
Keyword(s):  
Genetic Mapping ◽  
Trypanosoma Brucei ◽  
Complex Traits ◽  
Positional Cloning ◽  
Genetic Maps ◽  
Linkage Groups ◽  
Physical Size ◽  
Large Numbers ◽  
Number Of Genes ◽  
Allelic Segregation

The genome of the African trypanosome, Trypanosoma brucei , is currently being sequenced, raising the question of how the data generated can be used to determine the function of the large number of genes that will be identified. There is a range of possible approaches, and in this paper we discuss the use of a classical genetic approach coupled with positional cloning based on the ability of trypanosomes to undergo genetic exchange. The genetics of these parasites is essentially similar to a conventional diploid Mendelian system with allelic segregation and an independent assortment of markers on different chromosomes. Data are presented showing that recombination occurs between markers on the same chromosome allowing the physical size of the unit of recombination to be determined. Analysis of the available progeny clones from a series of crosses shows that, in principal, large numbers of progeny can readily be isolated from existing cryopreserved products of mating and, taking these findings together, it is clear that genetic mapping of variable phenotypes is feasible. The available phenotypes for analysis are outlined and most are relevant to the transmission and pathogenesis of the parasite. Genetic maps from two crosses are presented based on the use of the technique of AFLP; these maps comprise 146 and 139 markers in 30 and 21 linkage groups respectively. Segregation distortion is exhibited by some of the linkage groups and the possible reasons for this are discussed. The general conclusion, from the results presented, is that a genetic-mapping approach is feasible and will, in the future, allow the genes determining a number of important traits to be identified.

scholarly journals GENETIC MAPPING IN SACCHAROMYCES IV. MAPPING OF TEMPERATURE-SENSITIVE GENES AND USE OF DISOMIC STRAINS IN LOCALIZING GENES

Genetics ◽  
1973 ◽  
Vol 74 (1) ◽  
pp. 33-54
Author(s):  
R K Mortimer ◽  
D C Hawthorne
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Number ◽  
Genetic Mapping ◽  
Genetic Markers ◽  
Genetic Maps ◽  
Temperature Sensitive ◽  
Yeast Saccharomyces Cerevisiae ◽  
Haploid Chromosome Number ◽  
Number Of Genes

ABSTRACT Through use of tetrad, random spore, trisomic, and mitotic analysis procedures a large number of genes, including 48 new genetic markers, were studied for their locations on the genetic maps of the yeast Saccharomyces cerevisiae. Eighteen new centromere linked genes were discovered and all but one was located on various ones of the 16 previously-established chromosomes. Five fragments of linked genes were also assigned to chromosomes; four were located on known chromosomes while the fifth determined one arm of a new chromosome. The experiments indicate that seventeen is likely to be the haploid chromosome number in this yeast. Most chromosomes have been established by genetic means to be metacentric and their genetic lengths vary from 5 cM to approximately 400 cM. Functionally-related sets of genes generally were found to be dispersed over the genome.

scholarly journals GENETIC MAPPING IN SCHIZOSACCHAROMYCES POMBE BY MITOTIC AND MEIOTIC ANALYSIS AND INDUCED HAPLOIDIZATION

Genetics ◽  
1977 ◽  
Vol 87 (3) ◽  
pp. 471-489 ◽  
Author(s):  
Jürg Kohli ◽  
Herbert Hottinger ◽  
Peter Munz ◽  
Andre Strauss ◽  
Pierre Thuriaux
Keyword(s):  
Chromosome Number ◽  
Genetic Mapping ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Genetic Markers ◽  
Genetic Maps ◽  
Deficient Mutant ◽  
Linkage Groups ◽  
Meiotic Analysis ◽  
Haploid Chromosome Number

ABSTRACT The genetic maps of the fission yeast Schizosaccharomyces pombe were extended through the use of haploidization (spontaneous or induced by m-fluorophenylalanine), as well as by tetrad, random spore and mitotic analysis. A new diploidization method utilizing a meiosis-deficient mutant and improved haploidization techniques was employed. As a result of these and previous studies, 118 genetic markers have been assigned to 3 linkage groups. Centromere markers for all 3 chromosomes were identified and genetic maps containing a total of 71 genes were constructed. Our experiments indicate that 3 is very likely to be the haploid chromosome number of S. pombe.

Comparative genetic mapping of allotetraploid cotton and its diploid progenitors

Genome ◽  
1999 ◽  
Vol 42 (2) ◽  
pp. 184-203 ◽  
Author(s):  
C L Brubaker ◽  
A H Paterson ◽  
J F Wendel
Keyword(s):  
Fragment Length Polymorphism ◽  
Genetic Maps ◽  
Linkage Groups ◽  
Reciprocal Translocations ◽  
Physical Size ◽  
Cotton Species ◽  
A Genome ◽  
Duplicated Loci ◽  
Comparative Genetic Mapping ◽  
Allotetraploid Cotton

Allotetraploid cotton species (Gossypium) belong to a 1-2 million year old lineage that reunited diploid genomes that diverged from each other 5-10 million years ago. To characterize genome evolution in the diploids and allotetraploids, comparative RFLP mapping was used to construct genetic maps for the allotetraploids (AD genome; n = 26) and diploids (A and D genomes; n = 13). Comparisons among the 13 suites of homoeologous linkage groups permitted comparisons of synteny and gene order. Two reciprocal translocations were confirmed involving four allotetraploid At genome chromosomes, as was a translocation between the two extant A genome diploids. Nineteen locus order differences were detected among the two diploid and two allotetraploid genomes. Conservation of colinear linkage groups among the four genomes indicates that allopolyploidy in Gossypium was not accompanied by extensive chromosomal rearrangement. Many inversions include duplicated loci, suggesting that the processes that gave rise to inversions are not fully conservative. Allotetraploid At and Dt genomes and the A and D diploid genomes are recombinationally equivalent despite a nearly two-fold difference in physical size. Polyploidization in Gossypium is associated with enhanced recombination, as genetic lengths for allotetraploid genomes are over 50% greater than those of their diploid counterparts.Key words: restriction fragment length polymorphism (RFLP), Gossypium, evolution, polyploidy.

scholarly journals Joint Linkage and Linkage Disequilibrium Mapping in Natural Populations

Genetics ◽  
2001 ◽  
Vol 157 (2) ◽  
pp. 899-909
Author(s):  
Rongling Wu ◽  
Zhao-Bang Zeng
Keyword(s):  
Linkage Disequilibrium ◽  
Complex Traits ◽  
Positional Cloning ◽  
Genome Structure ◽  
Natural Populations ◽  
Linkage Disequilibrium Mapping ◽  
Linkage Disequilibria ◽  
Time Simulation ◽  
New Strategy ◽  
Fisher Scoring Algorithm

Abstract A new strategy for studying the genome structure and organization of natural populations is proposed on the basis of a combined analysis of linkage and linkage disequilibrium using known polymorphic markers. This strategy exploits a random sample drawn from a panmictic natural population and the open-pollinated progeny of the sample. It is established on the principle of gene transmission from the parental to progeny generation during which the linkage between different markers is broken down due to meiotic recombination. The strategy has power to simultaneously capture the information about the linkage of the markers (as measured by recombination fraction) and the degree of their linkage disequilibrium created at a historic time. Simulation studies indicate that the statistical method implemented by the Fisher-scoring algorithm can provide accurate and precise estimates for the allele frequencies, recombination fractions, and linkage disequilibria between different markers. The strategy has great implications for constructing a dense linkage disequilibrium map that can facilitate the identification and positional cloning of the genes underlying both simple and complex traits.

scholarly journals An enhanced molecular marker based genetic map of perennial ryegrass (Lolium perenne) reveals comparative relationships with other Poaceae genomes

Genome ◽  
2002 ◽  
Vol 45 (2) ◽  
pp. 282-295 ◽  
Author(s):  
Elizabeth S Jones ◽  
Natalia L Mahoney ◽  
Michael D Hayward ◽  
Ian P Armstead ◽  
J Gilbert Jones ◽  
...  
Keyword(s):  
Molecular Marker ◽  
Linkage Map ◽  
Genetic Map ◽  
Lolium Perenne ◽  
Perennial Ryegrass ◽  
Genetic Linkage Map ◽  
Population Based ◽  
Genetic Maps ◽  
Linkage Groups ◽  
Integrated Genetic Map

A molecular-marker linkage map has been constructed for perennial ryegrass (Lolium perenne L.) using a one-way pseudo-testcross population based on the mating of a multiple heterozygous individual with a doubled haploid genotype. RFLP, AFLP, isoenzyme, and EST data from four collaborating laboratories within the International Lolium Genome Initiative were combined to produce an integrated genetic map containing 240 loci covering 811 cM on seven linkage groups. The map contained 124 codominant markers, of which 109 were heterologous anchor RFLP probes from wheat, barley, oat, and rice, allowing comparative relationships between perennial ryegrass and other Poaceae species to be inferred. The genetic maps of perennial ryegrass and the Triticeae cereals are highly conserved in terms of synteny and colinearity. This observation was supported by the general agreement of the syntenic relationships between perennial ryegrass, oat, and rice and those between the Triticeae and these species. A lower level of synteny and colinearity was observed between perennial ryegrass and oat compared with the Triticeae, despite the closer taxonomic affinity between these species. It is proposed that the linkage groups of perennial ryegrass be numbered in accordance with these syntenic relationships, to correspond to the homoeologous groups of the Triticeae cereals.Key words: Lolium perenne, genetic linkage map, RFLP, AFLP, conserved synteny.

scholarly journals A genetic linkage map for the domesticated silkworm, Bombyx mori, based on restriction fragment length polymorphisms

1995 ◽  
Vol 66 (2) ◽  
pp. 109-126 ◽  
Author(s):  
Jinrui Shi ◽  
David G. Heckel ◽  
Marian R. Goldsmith
Keyword(s):  
Linkage Map ◽  
Bombyx Mori ◽  
Restriction Fragment ◽  
Fragment Length ◽  
Restriction Fragment Length Polymorphisms ◽  
Genetic Maps ◽  
Crossing Over ◽  
Linkage Groups ◽  
Length Polymorphisms ◽  
Restriction Fragment Length

SummaryWe present data for the initial construction of a molecular linkage map for the domesticated silkworm, Bombyx mori, based on 52 progeny from an F2 cross from a pair mating of inbred strains p50 and C108, using restriction fragment length polymorphisms (RFLPs). The map contains 15 characterized single copy sequences, 36 anonymous sequences derived from a follicular cDNA library, and 10 loci corresponding to a low copy number retrotransposon, mag. The 15 linkage groups and 8 ungrouped loci account for 23 of the 28 chromosomes and span a total recombination length of 413 cM; 10 linkage groups were correlated with established classic genetic maps. Scoring data from Southern blots were analysed using two Pascal programs written specifically to analyse linkage data in Lepidoptera, where females are the heterogametic sex and have achiasmatic meiosis (no crossing-over). These first examine evidence for linkage by calculating the maximum lod score under the hypothesis that the two loci are linked over the likelihood under the hypothesis that the two loci assort independently, and then determine multilocus linkage maps for groups of putatively syntenic loci by calculating the maximum likelihood estimate of the recombination fractions and the log likelihood using the EM algorithm for a specified order of loci along the chromosome. In addition, the possibility of spurious linkage was exhaustively tested by searching for genotypes forbidden by the absence of crossing-over in one sex.

Interactions betweenTrypanosoma bruceiandBabesiaspp. andPlasmodiumspp. in mice

Parasitology ◽  
1985 ◽  
Vol 90 (2) ◽  
pp. 241-254 ◽  
Author(s):  
Stephanie M. Millott ◽  
F. E. G. Cox
Keyword(s):  
Trypanosoma Brucei ◽  
Babesia Microti ◽  
Cell Populations ◽  
Time Interval ◽  
Oxygen Species ◽  
Plasmodium Chabaudi ◽  
Subsequent Infection ◽  
Activated Oxygen ◽  
Large Numbers ◽  
Intracellular Parasites

Swiss mice with chronicTrypanosoma bruceiinfections become refractory to subsequent infection withBabesia microtiandB. rodhaini. Infection withB. microti7 days afterT. bruceiresulted in an obvious inhibition of the babesia parasitaemias and this inhibition became more profound as the time interval between the infections increased, until at 17–20 days the parasitaemias were totally abolished. Even after intravenous injection of large numbers of parasites parasitaemias were inhibited. Similar inhibition was obtained in BALB/c mice but not in C57BL/6 mice. Mice with establishedT. bruceiinfections also showed reduced susceptibility toB. rodhaini. In mice similarly infected withT. bruceiand the malaria parasitesPlasmodium chabaudi chabaudiandP. c. adamithe pre-patent periods were noticeably prolonged but the subsequent parasitaemias were unaffected. Infections withP. yoeliiwere unaffected.Trypanosoma bruceiinfections were not affected by the intracellular parasites. Among the mechanisms investigated to explain these findings were changes in red blood cell populations, cross-reacting antigens, the release of toxic factors and the generation of activated oxygen species. None of these could account for the inhibition observed.

scholarly journals Genetic Power Calculator: design of linkage and association genetic mapping studies of complex traits

2003 ◽  
Vol 19 (1) ◽  
pp. 149-150 ◽  
Author(s):  
S. Purcell ◽  
S. S. Cherny ◽  
P. C. Sham
Keyword(s):  
Genetic Mapping ◽  
Complex Traits

scholarly journals Detection and Effects of a Homeologous Reciprocal Transposition in Brassica napus

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1569-1577
Author(s):  
Thomas C Osborn ◽  
David V Butrulle ◽  
Andrew G Sharpe ◽  
Kathryn J Pickering ◽  
Isobel A P Parkin ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Genetic Mapping ◽  
Doubled Haploid ◽  
Selective Advantage ◽  
F1 Hybrids ◽  
Rflp Markers ◽  
Cytological Analysis ◽  
Linkage Groups ◽  
Homeologous Chromosomes ◽  
Seed Yields

Abstract A reciprocal chromosomal transposition was identified in several annual oilseed Brassica napus genotypes used as parents in crosses to biennial genotypes for genetic mapping studies. The transposition involved an exchange of interstitial homeologous regions on linkage groups N7 and N16, and its detection was made possible by the use of segregating populations of doubled haploid lines and codominant RFLP markers. RFLP probes detected pairs of homeologous loci on N7 and N16 for which the annual and biennial parents had identical alleles in regions expected to be homeologous. The existence of an interstitial reciprocal transposition was confirmed by cytological analysis of synaptonemal complexes of annual × biennial F1 hybrids. Although it included approximately one-third of the physical length of the N7 and N16 chromosomes, few recombination events within the region were recovered in the progenies of the hybrids. Significantly higher seed yields were associated with the parental configurations of the rearrangement in segregating progenies. These progenies contained complete complements of homeologous chromosomes from the diploid progenitors of B. napus, and thus their higher seed yields provide evidence for the selective advantage of allopolyploidy through the fixation of intergenomic heterozygosity.

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