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Microsporidia branch at the base of eukaryotic phylogenies inferred from translation elongation factor 1alpha (EF-1alpha) sequences. Because these parasitic eukaryotes are fungi (or close relatives of fungi), it is widely accepted that fast-evolving microsporidian sequences are artifactually "attracted" to the long branch leading to the archaebacterial(More)
It has long been recognized that the rates of molecular evolution vary amongst sites in proteins. The usual model for rate heterogeneity assumes independent rate variation according to a rate distribution. In such models the rate at a site, although random, is assumed fixed throughout the evolutionary tree. Recent work by several groups has suggested that(More)
In theory, codon models that account for the dependence of nucleotide substitutions between codon positions as well as differences between synonymous and non-synonymous changes best describe the sequence evolution in protein coding genes. However, in practice we know little about the degree to which violations of the assumptions of codon model-based(More)
Understanding the early evolution and diversification of eukaryotes relies on a fully resolved phylogenetic tree. In recent years, most eukaryotic diversity has been assigned to six putative supergroups, but the evolutionary origin of a few major "orphan" lineages remains elusive. Two ecologically important orphan groups are the heterotrophic Telonemia and(More)
Cryptomonad algae acquired their plastids by the secondary endosymbiotic uptake of a eukaryotic red alga. Several other algal lineages acquired plastids through such an event [1], but cryptomonads are distinguished by the retention of a relic red algal nucleus, the nucleomorph [2]. The nucleomorph (and its absence in other lineages) can reveal a great deal(More)
Spliceosomal introns are hallmarks of most eukaryotic genomes and are excised from premature mRNAs by a spliceosome that is among the largest, and most complex, molecular machine in cells. The divergent unicellular eukaryote Giardia intestinalis, the causative agent of giardiasis, also possesses spliceosomes, but only four canonical (cis-spliced) introns(More)
Class 1 release factor in eukaryotes (eRF1) recognizes stop codons and promotes peptide release from the ribosome. The 'molecular mimicry' hypothesis suggests that domain 1 of eRF1 is analogous to the tRNA anticodon stem-loop. Recent studies strongly support this hypothesis and several models for specific interactions between stop codons and residues in(More)
It is generally accepted that new genes arise via duplication and functional divergence of existing genes, in accordance with Ohno's model, now called "Mutation During Redundancy," or MDR. In this model, one of the two gene copies is free to acquire novel (although likely related) activities through mutation, since only one copy is required for its original(More)
Flow is the holistic experience felt when an individual acts with total involvement. Although flow is likely associated with many functions of the prefrontal cortex (PFC), such as attention, emotion, and reward processing, no study has directly investigated the activity of the PFC during flow. The objective of this study was to examine activity in the PFC(More)
BACKGROUND Plastid replacements through secondary endosymbioses include massive transfer of genes from the endosymbiont to the host nucleus and require a new targeting system to enable transport of the plastid-targeted proteins across 3-4 plastid membranes. The dinoflagellates are the only eukaryotic lineage that has been shown to have undergone several(More)