Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “statistical genetics”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources
PubMedDate not supplied

Genetically induced mitotic exchange in the heterochromatin of Drosophila melanogaster.

Multiple copies of the 18S and 28S ribosomal RNA cistrons are present in both the X and Y chromosomes of Drosophila melanogaster. Data are presented here that identify a locus, Rex, that causes exchange-like events between duplicated ribosomal complexes at the ends of an attached-XY chromosome. Rex: (1) is close to or in the basal heterochromatin of the X chromosome; (2) is semidominant and (its effect) is temperature sensitive; (3) acts maternally; and (4) affects behavior of paternally derived attached-XY chromosomes shortly after fertilization. Though, at this point, the existence of Rex is known only from its effects on behavior of a particular compound chromosome, it presents intriguing possibilities for understanding regulation of chromosome behavior and organization of the ribosomal cistrons.

Animals↗
PubMed2003

Impact of selection, mutation rate and genetic drift on human genetic variation.

The accumulation of genome-wide information on single nucleotide polymorphisms in humans provides an unprecedented opportunity to detect the evolutionary forces responsible for heterogeneity of the level of genetic variability across loci. Previous studies have shown that history of recombination events has produced long haplotype blocks in the human genome, which contribute to this heterogeneity. Other factors, however, such as natural selection or the heterogeneity of mutation rates across loci, may also lead to heterogeneity of genetic variability. We compared synonymous and non-synonymous variability within human genes with their divergence from murine orthologs. We separately analyzed the non-synonymous variants predicted to damage protein structure or function and the variants predicted to be functionally benign. The predictions were based on comparative sequence analysis and, in some cases, on the analysis of protein structure. A strong correlation between non-synonymous, benign variability and non-synonymous human-mouse divergence suggests that selection played an important role in shaping the pattern of variability in coding regions of human genes. However, the lack of correlation between deleterious variability and evolutionary divergence shows that a substantial proportion of the observed non-synonymous single-nucleotide polymorphisms reduces fitness and never reaches fixation. Evolutionary and medical implications of the impact of selection on human polymorphisms are discussed.

Animals↗
PubMed1980

Pathogenesis of herpes simplex labialis. I. Replication of herpes simplex virus in cultures of epidermal cells from subjects with frequent recurrences.

Primary cultures were established with epidermal cells from the skin of 11 patients with frequent episodes of herpes simplex labialis and 13 control subjects with titers of neutralizing antibody to herpes simplex virus (HSV) type 1 but no history of herpetic disease. Confluent monolayers were exposed to HSV type 1 strain E115, and the infection was monitored by assay of the rate of virus appearance in the culture medium. The mean slope of the virus growth curves ([log10 pfu/ml]/log10 hr) was 9.0 in cultures from patients vs. 9.5 in cultures from controls, and the respective mean titers of virus 53 hr after infection were 10(6.8) and 10(6.5) (differences not statistically significant). Genetically controlled host factors may play some role in the clinical response to HSV infection, but variation in the susceptibility of epidermal cells, the natural target for HSV, is not one of the critical determinations.

Adult↗
PubMedDate not supplied

Asymptotic variances of QTL estimators with selective DNA pooling.

Investigation on QTL-marker linkage usually requires a great number of observed recombinations, inferred from combined analysis of phenotypes and genotypes. To avoid costly individual genotyping, inferences on QTL position and effects can instead make use of marker allele frequencies. DNA pooling of selected samples makes allele frequency estimation feasible for studies involving large sample sizes. Linkage studies in outbred populations have traditionally exploited half-sib family designs; within the animal production context, half-sibships provide large families that are highly suitable for DNA pooling. Estimators for QTL position and effect have been proposed that make use of information from flanking markers. We present formulas derived by the delta method for the asymptotic variance of these estimators.

Chromosome Mapping↗
PubMed2006

Structural determinants of the rate of protein evolution in yeast.

We investigate how a protein's structure influences the rate at which its sequence evolves. Our basic hypothesis is that proteins with highly designable structures (structures that are encoded by many sequences) will evolve more rapidly. Recent theoretical advances argue that structures with a higher density of interresidue contacts are more designable, and we show that high contact density is correlated with an increased rate of sequence evolution in yeast. In addition, we investigate the correlations between the rate of sequence evolution and several other structural descriptors, carefully controlling for the strong effect of expression level on evolutionary rate. Overall, we find that the structural descriptors that we consider appear to explain roughly 10% of the variation in rates of protein evolution in yeast. We also show that despite the well-known trend for buried residues to be more conserved, proteins with a higher fraction of buried residues, nonetheless, tend to evolve their sequences more rapidly. We suggest that this effect is due to the increased designability of structures with more buried residues. Our results provide evidence that protein structure plays an important role in shaping the rate of sequence evolution and provide evidence to support recent theoretical advances linking structural designability to contact density.

Analysis of Variance↗
PubMed1992

Analysis of nonuniformity in intron phase distribution.

The distribution of different intron groups with respect to phases has been analyzed. It has been established that group II introns and nuclear introns have a minimum frequency of phase 2 introns. Since the phase of introns is an extremely conservative measure the observed minimum reflects evolutionary processes. A sample of all known, group I introns was too small to provide a valid characteristic of their phase distribution. The findings observed for the unequal distribution of phases cannot be explained solely on the basis of the mobile properties of introns. One of the most likely explanations for this nonuniformity in the intron phase distribution is the process of exon shuffling. It is proposed that group II introns originated at the early stages of evolution and were involved in the process of exon shuffling.

Animals↗
PubMed1996

Preference for guanosine at first codon position in highly expressed Escherichia coli genes. A relationship with translational efficiency.

The variation in base composition at the three codon sites in relation to gene expressivity, the latter estimated by the Codon Adaptation Index, has been studied in a sample of 1371 Escherichia coli genes. Correlation and regression analyses show that increasing expression levels are accompanied by higher frequencies of base G at first, of base A at second and of base C at third codon positions. However, correlation between expressivity and base compositional biases at each codon site was only significant and positive at first codon position. The preference for G-starting codons as gene expression level increases is discussed in terms of translational optimization.

Amino Acids↗
PubMedDate not supplied

Litter sizes of Ha(ICR) mice: a preference for even numbers?

The frequency distributions of litter sizes at birth for eight sublines derived from the same Ha(ICR) mouse stock with or without selection for large litters have their modes at even numbers of young. Each of the eight sublines produced a majority of even-numbered litters. An upward integral shift relationship among the medians of the frequency distributions was established. These findings are interpreted to mean that, in response to continued plus selection, ovarian and uterine performance of the Ha(ICR) bipartite reproductive system tends to be maximal bilaterally, which results in an excess of even-numbered litter sizes.

Animals↗
PubMedDate not supplied

Comparison of crossbred and purebred selection for a heterotic trait in highly selected populations of Tribolium.

Selection on the basis of crossbred performance (RRS) was compared for 11 generations to within-line selection based on purebred performance (WLS) for a heterotic trait, 13-day larval weight in Tribolium populations previously subjected to 30 generations of purebred selection. RRS crossbreds gained slightly less than crossbreds of WLS populations. RRS purebreds showed a much smaller composite populations were greater than those observed for the continued populations. A model for the genetic control of larval weight is suggested in which there are both dominant and overdominant loci and homozygotes are less fit than heterozygotes.

Animals↗
PubMedDate not supplied

Inversion polymorphism in Drosophila obscura.

The inversion polymorphism of Drosophila obscura Fallen, a European species of the obscura group of the subgenus Sophophora, is described. A total of 21 inversions have been recorded; they are located in the five large chromosomes of the species (a dot chromosome is also present) and form 25 gene arrangements present in the species' natural populations. Strains from five different countries were studied. Two of these inversions were found to be pericentric, and the remaining were paracentric. The presence of "hot" points (multibreaks) was noticed. The distribution of the relative lengths of inversions conformed to the Van Valen-Levins distribution, contrary to what happens in D. subobscura. Observations also showed that there is no crossover inhibition between nonoverlapping inversions. The phylogeny of chromosome C was reconstructed; the existence of several arrangements not found was postulated; and the primitive gene arrangement, linking D. obscura to its closely related species was identified, as well as the primitive gene arrangements of the other chromosomes. Photographic maps of the chromosomes of D. obscura are provided here.

Animals↗
PubMed2001

Exploring the demographic history of DNA sequences using the generalized skyline plot.

We present an intuitive visual framework, the generalized skyline plot, to explore the demographic history of sampled DNA sequences. This approach is based on a genealogy inferred from the sequences and provides a nonparametric estimate of effective population size through time. In contrast to previous related procedures, the generalized skyline plot is more applicable to cases where the underlying tree is not fully resolved and the data is not highly variable. This is achieved by the grouping of adjacent coalescent intervals. We employ a small-sample Akaike information criterion to objectively choose the optimal grouping strategy. We investigate the performance of our approach using simulation and subsequently apply it to HIV-1 sequences from central Africa and mtDNA sequences from red pandas.

Africa↗