Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

In phylogenetics, the unrooted model of phylogeny and the strict molecular clock model are two extremes of a continuum. Despite their dominance in phylogenetic inference, it is evident that both are biologically unrealistic and that the real evolutionary process lies between these two extremes. Fortunately, intermediate models employing relaxed molecular clocks have been described. These models open the gate to a new field of “relaxed phylogenetics.” Here we introduce a new approach to performing relaxed phylogenetic analysis. We describe how it can be used to estimate phylogenies and divergence times in the face of uncertainty in evolutionary rates and calibration times. Our approach also provides a means for measuring the clocklikeness of datasets and comparing this measure between different genes and phylogenies. We find no significant rate autocorrelation among branches in three large datasets, suggesting that autocorrelated models are not necessarily suitable for these data. In addition, we place these datasets on the continuum of clocklikeness between a strict molecular clock and the alternative unrooted extreme. Finally, we present analyses of 102 bacterial, 106 yeast, 61 plant, 99 metazoan, and 500 primate alignments. From these we conclude that our method is phylogenetically more accurate and precise than the traditional unrooted model while adding the ability to infer a timescale to evolution.

/pdf/relaxed-phylogenetics-and-dating-with-confidence-5ez5tgzy1b.pdf

Relaxed Phylogenetics and Dating with Confidence

BIOE 402. Medical Technology Assessment. 2 or 3 hours. Bioentrepreneur course. Assessment of medical technology in the context of commercialization. Objectives, competition, market share, funding, pricing, manufacturing, growth, and intellectual property; many issues unique to biomedical products. Course Information: 2 undergraduate hours. 3 graduate hours. Prerequisite(s): Junior standing or above and consent of the instructor.

“Bioinformatics” 특집을 내면서

Genotypes are frequently used to identify parentage. Such analysis is notoriously vulnerable to genotyping error, and there is ongoing debate regarding how to solve this problem. Many scientists have used the computer program CERVUS to estimate parentage, and have taken advantage of its option to allow for genotyping error. In this study, we show that the likelihood equations used by versions 1.0 and 2.0 of CERVUS to accommodate genotyping error miscalculate the probability of observing an erroneous genotype. Computer simulation and reanalysis of paternity in Rum red deer show that correcting this error increases success in paternity assignment, and that there is a clear benefit to accommodating genotyping errors when errors are present. A new version of CERVUS (3.0) implementing the corrected likelihood equations is available at http://www.fieldgenetics.com.

Revising how the computer program CERVUS accommodates genotyping error increases success in paternity assignment.

The RefSeq project at the National Center for Biotechnology Information (NCBI) maintains and curates a publicly available database of annotated genomic, transcript, and protein sequence records (http://www.ncbi.nlm.nih.gov/refseq/). The RefSeq project leverages the data submitted to the International Nucleotide Sequence Database Collaboration (INSDC) against a combination of computation, manual curation, and collaboration to produce a standard set of stable, non-redundant reference sequences. The RefSeq project augments these reference sequences with current knowledge including publications, functional features and informative nomenclature. The database currently represents sequences from more than 55,000 organisms (>4800 viruses, >40,000 prokaryotes and >10,000 eukaryotes; RefSeq release 71), ranging from a single record to complete genomes. This paper summarizes the current status of the viral, prokaryotic, and eukaryotic branches of the RefSeq project, reports on improvements to data access and details efforts to further expand the taxonomic representation of the collection. We also highlight diverse functional curation initiatives that support multiple uses of RefSeq data including taxonomic validation, genome annotation, comparative genomics, and clinical testing. We summarize our approach to utilizing available RNA-Seq and other data types in our manual curation process for vertebrate, plant, and other species, and describe a new direction for prokaryotic genomes and protein name management.

Reference sequence (RefSeq) database at NCBI: current status, taxonomic expansion, and functional annotation

The human colonisation of Polynesia was a major event in world prehistory. It represents one of the last human population migrations, and one which required crossing major water barriers. Though the subject of Pacific population origins has been approached by scholars from numerous fields for nearly a century, recent years have seen the problem addressed by human geneticists [1–5]. Since the initial report describing the recovery of DNA from skeletal remains [6], ancient DNA studies have also focused on the Pacific region [7, 8]. In this paper we present the results of ancient DNA analyses of Rattus exulans, an animal that was transported by ancestral Polynesians through the Pacific to the far reaches of the Polynesian triangle. Analysis of DNA of R. exulans skeletal remains has many advantages over studies of ancient human remains, yet the one drawback has been the recovery of ancient DNA from single bones of these very small rodents. We have successfully modified standard extraction protocols for ancient DNA [9] and have consistently extracted, amplified and sequenced mitochondrial DNA (mtDNA) from less than 0.1 g of R. exulans bone and tooth samples recovered from archaeological sites throughout the Pacific, ranging from 400 to 2000 years old.

Ancient DNA from polynesian rats: Extraction, amplification and sequence from single small bones

A molecular phylogeny of New Zealand's Petroica (Aves: Petroicidae) species based on mitochondrial DNA sequences.

Functionalism, structuralism and ways of seeing

DNA-based sex tests now exist for many avian species. However, none of these tests are widely applicable to ratites. We present DNA sequence data for a locus that is W chromosome-linked in the kiwi, ostrich, cassowary, rhea, and emu. At the amino acid level, this sequence has significant homology to X-linked genes in platyfish and Caenorhabditis elegans. Polymerase chain reaction (PCR) primers designed to this locus allow the assignment of sex in all species of living ratites.

A DNA test to sex ratite birds.

Interpreting the levels of genetic diversity in organisms with diverse life and population histories can be difficult. The processes and mechanisms regulating this diversity are complex and still poorly understood. However, endangered species typically have low genetic variation as a consequence of the effects of genetic drift in small populations. In this study we examine genetic variation in the critically endangered Chatham Island Taiko (Tchaik, Pterodroma magentae), one of the world’s rarest seabirds. The Taiko has a very small population size of between 120 and 150 individuals, including just 8–15 breeding pairs. We report surprisingly high mitochondrial and nuclear genetic diversity in this critically endangered long-lived species. We hypothesise that the present Taiko population has retained a significant proportion of its past genetic diversity. However, it is also possible that undiscovered birds are breeding in unknown areas, which could increase the population size estimate. Importantly, from a conservation perspective, we show that the high level of variation is unlikely to be maintained in the future since chicks currently being born have only a limited number of the mitochondrial DNA haplotypes found in adults. Reduced genetic variation will mean that our ability to infer past events and the population history of Taiko using genetics could soon be lost and the power to determine, for example, parentage and other close order relationships will be diminished. Therefore, the maintenance of genetic diversity in future generations is an important consideration for conservation management of the Taiko.

/pdf/high-mitochondrial-and-nuclear-genetic-diversity-in-one-of-pjn8wsdbdi.pdf

David M. Lambert

Papers

Ancient DNA from polynesian rats: Extraction, amplification and sequence from single small bones

A molecular phylogeny of New Zealand's Petroica (Aves: Petroicidae) species based on mitochondrial DNA sequences.

Functionalism, structuralism and ways of seeing

A DNA test to sex ratite birds.

High mitochondrial and nuclear genetic diversity in one of the world’s most endangered seabirds, the Chatham Island Taiko (Pterodroma magentae)