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1.
Molecular population genetics and evolution   总被引:2,自引:0,他引:2       下载免费PDF全文
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Anderson JA  Song YS  Langley CH 《Genetics》2008,178(1):477-487
DNA sequence surveys in yeast and humans suggest that the forces shaping telomeric polymorphism and divergence are distinctly more dynamic than those in the euchromatic, gene-rich regions of the chromosomes. However, the generality of this pattern across outbreeding, multicellular eukaryotes has not been determined. To characterize the structure and evolution of Drosophila telomeres, we collected and analyzed molecular population genetics data from the X chromosome subtelomere in 58 lines of North American Drosophila melanogaster and 29 lines of African D. melanogaster. We found that Drosophila subtelomeres exhibit high levels of both structural and substitutional polymorphism relative to linked euchromatic regions. We also observed strikingly different patterns of variation in the North American and African samples. Moreover, our analyses of the polymorphism data identify a localized hotspot of recombination in the most-distal portion of the X subtelomere. While the levels of polymorphism decline sharply and in parallel with rates of crossing over per physical length over the distal first euchromatic megabase pairs of the X chromosome, our data suggest that they rise again sharply in the subtelomeric region (approximately 80 kbp). These patterns of historical recombination and geographic differentiation indicate that, similar to yeast and humans, Drosophila subtelomeric DNA is evolving very differently from euchromatic DNA.  相似文献   

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Molecular basis and population genetics of phenylketonuria   总被引:14,自引:0,他引:14  
S L Woo 《Biochemistry》1989,28(1):1-7
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Dr  P. Chardon 《Animal genetics》1989,20(1):84-111
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Kovacevic M  Schaeffer SW 《Genetics》2000,156(1):155-172
This article presents a nucleotide sequence analysis of 500 bp determined in each of five X-linked genes, runt, sisterlessA, period, esterase 5, and Heat-shock protein 83, in 40 Drosophila pseudoobscura strains collected from two populations. Estimates of the neutral migration parameter for the five loci show that gene flow among D. pseudoobscura populations is sufficient to homogenize inversion frequencies across the range of the species. Nucleotide diversity at each locus fails to reject a neutral model of molecular evolution. The sample of 40 chromosomes included six Sex-ratio inversions, a series of three nonoverlapping inversions that are associated with a strong meiotic drive phenotype. The selection driven by the Sex-ratio meiotic drive element has not fixed variation across the X chromosome of D. pseudoobscura because, while significant linkage disequilibrium was observed within the sisterlessA, period, and esterase 5 genes, we did not find evidence for nonrandom association among loci. The Sex-ratio chromosome was estimated to be 25,000 years old based on the decomposition of linkage disequilibrium between esterase 5 and Heat-shock protein 83 or 1 million years old based on the net divergence of esterase 5 between Standard and Sex-ratio chromosomes. Genetic diversity was depressed within esterase 5 within Sex-ratio chromosomes, while the four other genes failed to show a reduction in heterozygosity in the Sex-ratio background. The reduced heterogeneity in esterase 5 is due either to its location near one of the Sex-ratio inversion breakpoints or that it is closely linked to a gene or genes responsible for the Sex-ratio meiotic drive system.  相似文献   

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While many functional elements of the meiotic process are well characterized in model organisms, the genetic basis of most of the natural phenotypic variation observed in meiotic pathways has not been determined. To begin to address this issue, we characterized patterns of polymorphism and divergence in the protein-coding regions of 33 genes across 31 lines of Drosophila melanogaster and 6 lines of Drosophila simulans. We sequenced genes known to be involved in chromosome segregation, recombination, DNA repair, and related heterochromatin binding. As expected, we found several of the genes to be highly conserved, consistent with purifying selection. However, a subset of genes showed patterns of polymorphism and divergence typical of other types of natural selection. Moreover, several intriguing differences between the two Drosophila lineages were evident: along the D. simulans lineage we consistently found evidence of adaptive protein evolution, whereas along the D. melanogaster lineage several loci exhibited patterns consistent with the maintenance of protein variation.  相似文献   

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Drosophila seminal proteins have an unusually high rate of molecular sequence evolution, suggesting either a high rate of neutral substitution or rapid adaptive evolution. To further quantify patterns of polymorphism and divergence in genes encoding seminal proteins, also called accessory gland proteins (Acp's), we conducted a sequencing survey of 10 Acp genes in samples of Drosophila melanogaster and D. simulans (Acp29AB, Acp32CD, Acp33A, Acp36DE, Acp53Ea, Acp62F, Acp63F, Acp76A, Acp95EF, and Acp98AB). Mean heterozygosity at replacement sites in D. simulans was 0.0074 for Acp genes and 0.0013 for a set of 19 non-Acp genes, and mean melanogaster-simulans divergence at replacement sites was 0.0497 for Acp genes and 0.0107 at non-Acp genes. The elevated divergence of Acp genes is thus accompanied by elevated within-species polymorphism. In addition to the already-reported departures of Acp26A, Acp29AB, and Acp70A from neutrality, our data reject neutrality at Acp29AB and Acp36DE in the direction of excess replacements in interspecific comparisons.  相似文献   

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Molecular genetics of Thiobacillus ferrooxidans.   总被引:9,自引:0,他引:9       下载免费PDF全文
Thiobacillus ferrooxidans is a gram-negative, highly acidophilic (pH 1.5 to 2.0), autotrophic bacterium that obtains its energy through the oxidation of ferrous iron or reduced inorganic sulfur compounds. It is usually dominant in the mixed bacterial populations that are used industrially for the extraction of metals such as copper and uranium from their ores. More recently, these bacterial consortia have been used for the biooxidation of refractory gold-bearing arsenopyrite ores prior to the recovery of gold by cyanidation. The commercial use of T. ferrooxidans has led to an increasing interest in the genetics and molecular biology of the bacterium. Initial investigations were aimed at determining whether the unique physiology and specialized habitat of T. ferrooxidans had been accompanied by a high degree of genetic drift from other gram-negative bacteria. Early genetic studies were comparative in nature and concerned the isolation of genes such as nifHDK, glnA, and recA, which are widespread among bacteria. From a molecular biology viewpoint, T. ferrooxidans appears to be a typical member of the proteobacteria. In most instances, cloned gene promoters and protein products have been functional in Escherichia coli. Although T. ferrooxidans has proved difficult to transform with DNA, research on indigenous plasmids and the isolation of the T. ferrooxidans merA gene have resulted in the development of a low-efficiency electroporation system for one strain of T. ferrooxidans. The most recent studies have focused on the molecular genetics of the pathways associated with nitrogen metabolism, carbon dioxide fixation, and components of the energy-producing mechanisms.  相似文献   

15.
Insects respond to septic infection in part by producing a suite of antimicrobial peptides that may be subject to host-pathogen coevolutionary dynamics. In order to infer population genetic forces acting on Drosophila antibacterial peptide genes, we examine global properties of polymorphism and divergence in the Drosophila melanogaster defensin, drosocin, metchnikowin, attacin C, diptericin A, and cecropin A, B, and C genes. As a functional class, antibacterial peptides exhibit low levels of interspecific amino acid divergence. There are multiple amino acid polymorphisms segregating within D. melanogaster, however, a high proportion of which change the charge or polarity of the variable residue. These polymorphisms are particularly prevalent in processed signal and propeptide domains. We find that models of coevolutionary "arms races" and selectively maintained hypervariability do not adequately describe the population dynamics of mature antibacterial peptides in D. melanogaster, but that a highly significant excess of high-frequency derived polymorphisms coupled with substantial intralocus linkage disequilibrium suggests that positive selection may act on antibacterial peptide genes. Some attributes of the data may be consistent with a simple demographic model of population founding followed by expansion, but departures from the equilibrium null tend to be more pronounced in the peptide genes than at other loci around the genome.  相似文献   

16.
Molecular population genetics and the search for adaptive evolution in plants   总被引:22,自引:0,他引:22  
The first papers on plant molecular population genetics were published approximately 10 years ago. Since that time, well over 50 additional studies of plant nucleotide polymorphism have been published, and many of these studies focused on detecting the signature of balancing or positive selection at a locus. In this review, we discuss some of the theoretical and statistical issues surrounding the detection of selection, with focus on plant populations, and we also summarize the empirical plant molecular population genetics literature. At face value, the literature suggests that a history of balancing or positive selection in plant genes is rampant. In two well-studied taxa (maize and Arabidopsis) over 20% of studied genes have been interpreted as containing the signature of selection. We argue that this is probably an overstatement of the prevalence of natural selection in plant genomes, for two reasons. First, demographic effects are difficult to incorporate and have generally not been well integrated into the plant population genetics literature. Second, the genes studied to date are not a random sample, so selected genes may be overrepresented. The next generation of studies in plant molecular population genetics requires additional sampling of local populations, explicit comparisons among loci, and improved theoretical methods to control for demography. Eventually, candidate loci should be confirmed by explicit consideration of phenotypic effects.  相似文献   

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Molecular genetics of vascular malformations.   总被引:4,自引:0,他引:4  
Vascular malformations are localized errors of angiogenic development. Most are cutaneous and are called vascular 'birthmarks'. These anomalies are usually obvious in the newborn, grow commensurately with the child, and gradually expand in adulthood (Mulliken and Glowacki, 1982). Vascular malformations also occur in visceral organs, such as the respiratory and gastrointestinal tract, but are more common in the brain (Mulliken and Young, 1988). These anomalies are composed of tortuous vascular channels of varying size and shape, lined by a continuous endothelium and surrounded by abnormal complement of mural cells. Vascular malformation can be life threatening due to obstruction, bleeding or congestive heart failure. Most anomalies occur sporadically, but there are families exhibiting autosomal dominant inheritance. Genetic studies of such families have resulted in the identification of mutated genes, directly giving proof of their important role in the regulation of angiogenesis.  相似文献   

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