Acquired Characters. See Inheritance of Acquired Characters Adoption
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Chromosomal Evolution in Raphicerus Antelope Suggests Divergent X
www.nature.com/scientificreports OPEN Chromosomal evolution in Raphicerus antelope suggests divergent X chromosomes may drive speciation through females, rather than males, contrary to Haldane’s rule Terence J. Robinson1*, Halina Cernohorska2, Svatava Kubickova2, Miluse Vozdova2, Petra Musilova2 & Aurora Ruiz‑Herrera3,4 Chromosome structural change has long been considered important in the evolution of post‑zygotic reproductive isolation. The premise that karyotypic variation can serve as a possible barrier to gene fow is founded on the expectation that heterozygotes for structurally distinct chromosomal forms would be partially sterile (negatively heterotic) or show reduced recombination. We report the outcome of a detailed comparative molecular cytogenetic study of three antelope species, genus Raphicerus, that have undergone a rapid radiation. The species are largely conserved with respect to their euchromatic regions but the X chromosomes, in marked contrast, show distinct patterns of heterochromatic amplifcation and localization of repeats that have occurred independently in each lineage. We argue a novel hypothesis that postulates that the expansion of heterochromatic blocks in the homogametic sex can, with certain conditions, contribute to post‑ zygotic isolation. i.e., female hybrid incompatibility, the converse of Haldane’s rule. This is based on the expectation that hybrids incur a selective disadvantage due to impaired meiosis resulting from the meiotic checkpoint network’s surveillance of the asymmetric expansions of heterochromatic blocks in the homogametic sex. Asynapsis of these heterochromatic regions would result in meiotic silencing of unsynapsed chromatin and, if this persists, germline apoptosis and female infertility. Te chromosomal speciation theory 1,2 also referred to as the “Hybrid dysfunction model”3, has been one of the most intriguing questions in biology for decades. -
Gabriel Dover)
Dear Mr Darwin (Gabriel Dover) Home | Intro | About | Feedback | Prev | Next | Search Steele: Lamarck's Was Signature Darwin Wrong? Molecular Drive: the Third Force in evolution Geneticist Gabriel Dover claims that there is a third force in evolution: 'Molecular Drive' beside natural selection and neutral drift. Molecular drive is operationally distinct from natural selection and neutral drift. According to Dover it explains biological phenomena, such as the 700 copies of a ribosomal RNA gene and the origin of the 173 legs of the centipede, which natural selection and neutral drift alone cannot explain. by Gert Korthof version 1.3 24 Mar 2001 Were Darwin and Mendel both wrong? Molecular Drive is, according to Dover, an important factor in evolution, because it shapes the genomes and forms of organisms. Therefore Neo-Darwinism is incomplete without Molecular Drive. It is no wonder that the spread of novel genes was ascribed to natural selection, because it was the only known process that could promote the spread of novel genes. Dover doesn't reject the existence of natural selection but points out cases where natural selection clearly fails as a mechanism. Molecular drive is a non-Darwinian mechanism because it is independent of selection. We certainly need forces in evolution, since natural selection itself is not a force. It is the passive outcome of other processes. It is not an active process, notwithstanding its name. Natural selection as an explanation is too powerful for its own good. Molecular drive is non-Mendelian because some DNA segments are multiplied disproportional. In Mendelian genetics genes are present in just two copies (one on the maternal and one on the paternal chromosome). -
Phylogenetic Systematics and the Evolutionary History of Some Intestinal Flatworm Parasites (Trematoda: Digenea: Plagiorchi01dea) of Anurans
PHYLOGENETIC SYSTEMATICS AND THE EVOLUTIONARY HISTORY OF SOME INTESTINAL FLATWORM PARASITES (TREMATODA: DIGENEA: PLAGIORCHI01DEA) OF ANURANS by RICHARD TERENCE 0'GRADY B.Sc, University Of British Columbia, 1978 M.Sc, McGill University, 1981 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES Department Of Zoology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March 1987 © Richard Terence O'Grady, 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Zoology The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: March 24, 1987 i i Abstract Historical structuralism is presented as a research program in evolutionary biology. It uses patterns of common ancestry as initial hypotheses in explaining evolutionary history. Such patterns, represented by phylogenetic trees, or cladograms, are postulates of persistent ancestral traits. These traits are evidence of historical constraints on evolutionary change. Patterns and processes consistent with a cladogram are considered to be consistent with an initial hypothesis of historical constraint. As an application of historical structuralism, a phylogenetic analysis is presented for members of the digenean plagiorchioid genera Glypthelmins Stafford, 1905 and Haplometrana Lucker, 1931. -
Molecular Evolution
SYSTEMATICS & EVOLUTION Molecular Evolution GINCY C GEORGE (Assistant Professor On Contract) Molecular Evolution Molecular Evolution • Molecular evolution is the area of evolutionary biology that studies evolutionary change at the level of the DNA sequence. Molecular Evolution • It includes the study of rates of sequence change, relative importance of adaptive and neutral changes, and changes in genome structure. Molecular evolution examines DNA and proteins, addressing two types of questions: How do DNA and proteins evolve? How are genes and organisms evolutionarily related? Study of how genes and proteins evolve and how are organisms related based on their DNA sequence • Molecular evolution therefore is the determination and comparative study of DNA and deduced amino acid sequences. • Sequences from different organisms or populations are matched or aligned • Evolution at molecular level is observable at the base (nucleotide) level changes in the DNA and amino acid changes in proteins • Both can be studied by examining the differences between species • Both polymorphism and evolutionary changes between species can be explained by two processes ie; • Natural selection and Neutral drift • The main factors that influence Natural selection and Neutral drift are population size and the selection coefficient of the different genotypes • If the population is small and the selection coefficient low; genetic drift dominates, • Whereas natural selection dominates if the population and selection coefficients are large • Evolution of Modern species -
Concerted Evolution at the Population Level: Pupfish Hindill Satellite DNA Sequences JOHN F
Proc. Nati. Acad. Sci. USA Vol. 91, pp. 994-998, February 1994 Evolution Concerted evolution at the population level: Pupfish HindIll satellite DNA sequences JOHN F. ELDER, JR.* AND BRUCE J. TURNER Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 Communicated by Bruce Wallace, October 18, 1993 ABSTRACT The canonical monomers (170 bp) of an organisms. There are very little data on their variation within abundant (1.9 x 10' copies per diploid genome) satellite DNA or divergence among conspecific natural populations. sequence family In the genome of Cyprinodon wriegau, a We report here sequence comparisons ofthe predominant "pph" that ranges along the Atlantic coast fom Cape Cod or "canonical" monomers of a satellite DNA array in sam- to central Mexico, are divergent in base sequence in 10 of 12 ples of 12 natural populations of Cyprinodon variegatus smle collected from natural populations. The divergence (Cyprinodontidae), a coastal killifish species. Ten of these Involves sbsitions, deletis, and insertions, is marked in samples have distinctive and characteristic canonical mono- scoe (mean pairwise sequence slarit = 61.6%; range = mers with high levels of intraindividual and intrapopulation 35-95.9%), Is largely ed to the 3' half of the monomer, homogeneity.t In other words, this satellite DNA has appar- and Is not correlated with the disace among cllg sites. ently undergone concerted evolution at or near the level of Repetitive loning and direct genomic sequencing expriments the local population. failed to detect intrapopulation and intraindividual variation, A preliminary account of some of our early findings has hig levels of sequence homogeneity within popu- appeared in a symposium volume (6). -
Soft Inheritance: Challenging the Modern Synthesis
Genetics and Molecular Biology, 31, 2, 389-395 (2008) Copyright © 2008, Sociedade Brasileira de Genética. Printed in Brazil www.sbg.org.br Review Article Soft inheritance: Challenging the Modern Synthesis Eva Jablonka1 and Marion J. Lamb2 1The Cohn Institute for the History and Philosophy of Science and Ideas, Tel-Aviv University, Tel-Aviv, Israel. 211 Fernwood, Clarence Road, London, United Kingdom. Abstract This paper presents some of the recent challenges to the Modern Synthesis of evolutionary theory, which has domi- nated evolutionary thinking for the last sixty years. The focus of the paper is the challenge of soft inheritance - the idea that variations that arise during development can be inherited. There is ample evidence showing that phenotypic variations that are independent of variations in DNA sequence, and targeted DNA changes that are guided by epigenetic control systems, are important sources of hereditary variation, and hence can contribute to evolutionary changes. Furthermore, under certain conditions, the mechanisms underlying epigenetic inheritance can also lead to saltational changes that reorganize the epigenome. These discoveries are clearly incompatible with the tenets of the Modern Synthesis, which denied any significant role for Lamarckian and saltational processes. In view of the data that support soft inheritance, as well as other challenges to the Modern Synthesis, it is concluded that that synthesis no longer offers a satisfactory theoretical framework for evolutionary biology. Key words: epigenetic inheritance, hereditary variation, Lamarckism, macroevolution, microevolution. Received: March 18, 2008; Accepted: March 19, 2008. Introduction 1. Heredity occurs through the transmission of germ- There are winds of change in evolutionary biology, line genes. -
The Yeast Sup35nm Domain Propagates As a Prion in Mammalian Cells Carmen Krammera, Dmitry Kryndushkinb, Michael H
The yeast Sup35NM domain propagates as a prion in mammalian cells Carmen Krammera, Dmitry Kryndushkinb, Michael H. Suhrec, Elisabeth Kremmerd, Andreas Hofmanne, Alexander Pfeifere, Thomas Scheibelc, Reed B. Wicknerb, Hermann M. Scha¨ tzla, and Ina Vorberga,1 aInstitute of Virology, Technische Universita¨t Mu¨ nchen, Trogerstrasse 30, 81675 Munich, Germany; bLaboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892; cLehrstuhl fu¨r Biomaterialien, Geba¨ude FAN/D, Universita¨t Bayreuth, Universita¨tsstrasse 30, 95447 Bayreuth, Germany; dInstitute of Molecular Immunology, Helmholtz Zentrum Mu¨nchen, Marchioninistrasse 25, 81377 Munich, Germany; and eInstitute of Pharmacology and Toxicology, Universita¨t Bonn, Reuterstrasse 2b, 53113 Bonn, Germany Contributed by Reed B. Wickner, November 13, 2008 (sent for review October 13, 2008) Prions are infectious, self-propagating amyloid-like protein aggre- for Sup35p aggregation (12). Stable maintenance of yeast prions gates of mammals and fungi. We have studied aggregation propen- relies on the activity of a variety of molecular chaperones (13). sities of a yeast prion domain in cell culture to gain insights into Deletion of the heat shock protein Hsp104 cures all known naturally general mechanisms of prion replication in mammalian cells. Here, we occurring yeast prions, strongly emphasizing its crucial role in prion report the artificial transmission of a yeast prion across a phylogenetic biogenesis (14). In concert with other heat shock factors, Hsp104 is kingdom. HA epitope-tagged yeast Sup35p prion domain NM was capable of disaggregating aberrant protein aggregates, and thereby stably expressed in murine neuroblastoma cells. Although cytosoli- likely generates prion seeds that can be passed on to daughter cells cally expressed NM-HA remained soluble, addition of fibrils of bac- (5, 15). -
Molecular Facts and Evolutionary Theory
Journal and Proceedings of The Royal Society of New South Wales Volume 120 Parts 1 and 2 [Issued September, 1987] pp.39-48 Return to CONTENTS Molecular Facts and Evolutionary Theory George L. Gabor Miklos Evolutionary biology has had a fascinating recent history. It was realized more than a century ago that the way of approaching many evolutionary problems lay in studies of morphology. However, as pointed out by Bateson in 1922, “discussions of evolution came to an end primarily because no progress was being made. Morphology having been explored in the minutest corners, we turned elsewhere. We became geneticists in the conviction that there at least must evolutionary wisdom be found.” At the same time, while it was clear that morphology must have its bases in embryology, it was instead the mathematically oriented theory of neo-Darwinism that rose to prominence over the next half century. This theory is essentially an amalgam of Mendelian genetics and classical Darwinian selection, firmly based on changes in gene frequencies at particular loci. In the late 1960s, it began to be evaluated at a crude molecular level using gel electrophoresis techniques that allowed the examination of polymorphisms at many enzyme coding loci. In the mid 1970s the technological advances of genetic engineering ushered in an entirely new era of molecular biology. The molecular biologist became the successor to the pure geneticist, and the focus switched back to the molecular analysis of development. The molecular biology of recombinant DNA revolutionized the previous concepts of genome organization and function and led to a reappraisal of the importance of neo-Darwinism. -
Cross.Corrected.Pdf (1.066Mb)
iii ANALYSIS OF THE HERITABILITY OF CORTICAL INVERSIONS THROUGH SEXUAL EXCHANGE IN Paramecium tetraurelia A Senior Scholars Thesis by REBECCA KANG CROSS Submitted to Honors and Undergraduate Research Texas A&M University in partial fulfillment of the requirements for the designation as UNDERGRADUATE RESEARCH SCHOLAR May 2012 Major: Molecular and Cell Biology iii ANALYSIS OF THE HERITABILITY OF CORTICAL INVERSIONS THROUGH SEXUAL EXCHANGE IN Paramecium tetraurelia A Senior Scholars Thesis by REBECCA KANG CROSS Submitted to Honors and Undergraduate Research Texas A&M University in partial fulfillment of the requirements for the designation as UNDERGRADUATE RESEARCH SCHOLAR Approved by: Research Advisor: Karl Aufderheide Associate Drirector, Honors and Undergraduate Research: Duncan MacKenzie May 2012 Major: Molecular and Cell Biology iii ABSTRACT Analysis of the Heritability of Cortical Inversions through Sexual Exchange in Paramecium tetraurelia. (May 2012) Rebecca Kang Cross Department of Biology Texas A&M University Research Advisor: Dr. Karl Aufderheide Department of Biology Paramecium tetraurelia is a large, single-celled, ciliated protist. Short cell cycle times (4.5-5 hours) and manipulable Mendelian genetics have made it an attractive research species, particularly for developmental genetics investigations. A genetic cross between cells with inverted ciliary rows and cells with normal cortexes was performed to determine the heritability of cortical inversions through sexual exchange in P. tetraurelia. A nuclear gene, nd6, which confers trichocyst nondischarge, was used in the cross to demonstrate a Mendelian inheritance pattern. Quantitative scoring of cortical phenotypes, including the location and size of the inversion, and the total number of ciliary rows was performed for the P1, F1, and F2 generations. -
Dancing with DNA and Flirting with the Ghost of Lamarck
Biology and Philosophy (2007) 22:439–451 Ó Springer 2006 DOI 10.1007/s10539-006-9034-x Book review Dancing with DNA and flirting with the ghost of Lamarck MARY JANE WEST-EBERHARD Smithsonian Tropical Research Institute, c/o Escuela de Biologı´a, Cı`udad Unı`versitaria, Costa Rica (e-mail: [email protected]; phone: +506-228-0001; fax: +506-228-0001) Review of: Evolution in Four Dimensions, Eva Jablonka and Marion J. Lamb, 2005, MIT Press, Cambridge, Massachusetts Evolution in Four Dimensions, by Eva Jablonka and Marion Lamb, is a dis- armingly good-humored book that challenges the overly gene-centered ‘Neo- Darwinian’ (mid-20th-Century-Synthesis) view of evolution via selection on phenotypes affected by random changes in DNA. Their remedy, more palat- able by the end of the book than I expected at the beginning, is to propose that we revise and expand our ‘‘unidimensional’ vision of heredity. Heredity, they argue, occurs in four dimensions: genetic inheritance, the conventionally rec- ognized mode of inheritance via transmission of DNA; epigenetic inheritance, or transmission of non-genetic information from parental cells to daughter cells, as in the cytoplasm of an egg; behavioral inheritance, or cultural trans- mission of learned traits; and symbolic transmission of information by means of abstract representation, especially language in humans. All four modes of inheritance provide variants on which natural selection can act. Therefore they portray evolution as occurring in four dimensions, corresponding to the four dimensions of inheritance. The style of the book makes it accessible to an educated lay reader. The text has been unburdened by removal of bibliographic citations to a single section of notes at the end of the book, and by a series of dialogues with a make-believe Devil’s advocate named Ifcha Mistabra (in Aramaic, ‘‘The opposite conjecture’’), where the authors anticipate and answer potential confusions and objections to their main points. -
Paramecium Tetraurelia Basal Body Structure Anne‑Marie Tassin*, Michel Lemullois and Anne Aubusson‑Fleury
Tassin et al. Cilia (2016) 5:6 DOI 10.1186/s13630-016-0026-4 Cilia REVIEW Open Access Paramecium tetraurelia basal body structure Anne‑Marie Tassin*, Michel Lemullois and Anne Aubusson‑Fleury Abstract Paramecium is a free-living unicellular organism, easy to cultivate, featuring ca. 4000 motile cilia emanating from lon‑ gitudinal rows of basal bodies anchored in the plasma membrane. The basal body circumferential polarity is marked by the asymmetrical organization of its associated appendages. The complex basal body plus its associated rootlets forms the kinetid. Kinetids are precisely oriented within a row in correlation with the cell polarity. Basal bodies also display a proximo-distal polarity with microtubule triplets at their proximal ends, surrounding a permanent cartwheel, and microtubule doublets at the transition zone located between the basal body and the cilium. Basal bodies remain anchored at the cell surface during the whole cell cycle. On the opposite to metazoan, there is no centriolar stage and new basal bodies develop anteriorly and at right angle from the base of the docked ones. Ciliogenesis follows a spe‑ cific temporal pattern during the cell cycle and both unciliated and ciliated docked basal bodies can be observed in the same cell. The transition zone is particularly well organized with three distinct plates and a maturation of its struc‑ ture is observed during the growth of the cilium. Transcriptomic and proteomic analyses have been performed in different organisms including Paramecium to understand the ciliogenesis process. The data have incremented a multi- organism database, dedicated to proteins involved in the biogenesis, composition and function of centrosomes, basal bodies or cilia. -
Unicellular Eukaryotes As Models in Cell and Molecular Biology
Unicellular Eukaryotes as Models in Cell and Molecular Biology: Critical Appraisal of Their Past and Future Value Martin Simon*, Helmut Plattner†,1 *Molecular Cellular Dynamics, Centre of Human and Molecular Biology, Saarland University, Saarbru¨cken, Germany †Faculty of Biology, University of Konstanz, Konstanz, Germany 1Corresponding author: e-mail address: [email protected] Contents 1. Introduction 142 2. What is Special About Unicellular Models 143 2.1 Unicellular models 144 2.2 Unicellular models: Examples, pitfals, and perspectives 148 3. Unicellular Models for Organelle Biogenesis 151 3.1 Biogenesis of mitochondria in yeast 152 3.2 Biogenesis of secretory organelles, cilia, and flagella 152 3.3 Phagocytotic pathway 153 3.4 Qualifying for model system by precise timing 155 3.5 Free-living forms as models for pathogenic forms 157 4. Models for Epigenetic Phenomena 158 4.1 Epigenetic phenomena from molecules to ultrastructure 161 4.2 Models for RNA-mediated epigenetic phenomena 163 4.3 Excision of IESs during macronuclear development: scnRNA model 170 4.4 Maternal RNA controlling DNA copy number 172 4.5 Maternal RNA matrices providing template for DNA unscrambling in Oxytricha 172 4.6 Impact of epigenetic studies with unicellular models 173 5. Exploring Potential of New Model Systems 175 5.1 Human diseases as new models 175 5.2 Protozoan models: Once highly qualified Now disqualified? 178 5.3 Boon and bane of genome size: Small versus large 179 5.4 Birth and death of nuclei, rather than of cells 183 5.5 Special aspects 184 6. Epilogue 185 Acknowledgment 186 References 186 141 142 Abstract Unicellular eukaryotes have been appreciated as model systems for the analysis of cru- cial questions in cell and molecular biology.