Open Access Medical Books

MEIOSIS

MEIOSIS

Edited by Carol Bernstein and Harris Bernstein .

132 pages .
Open Access .
ISBN 978-953-51-1197-9 .


Meiosis is the key process underlying sexual reproduction in eukaryotes, occurring in single-celled eukaryotes and in most multicellular eukaryotes including animals and most plants. Thus meiosis is of considerable interest, both at the scientific level and at the level of natural human curiosity about sexual reproduction. Improved understanding of important aspects of meiosis has emerged in recent years and major questions are starting to be answered, such as “How does meiosis occur at the molecular level?”, “How did meiosis and sex arise during evolution?”, “What is the major adaptive function of meiosis and sex?”. In addition, changing perspectives on meiosis and sex have led to the question: “How should meiosis be taught?” .
The first chapter in this book reviews a number of recent studies indicating that doublestranded DNA molecules can distinguish “self” from “non-self” and consequently can undergo self-assembly in a pair-wise manner even in a solution of heterogeneous doublestranded DNA species. These studies used experimental approaches involving electrophoretic analysis and atomic force microscopy, analysis of liquid-crystalline aggregates, and a technique involving parallel single molecule magnetic tweezers applied to isolated double-stranded DNA. In addition, this chapter reviewed evidence that this type of selective association between homologous DNA molecules also applies to nucleosomes.
Self-assembly of homologous double-stranded DNA molecules and homologous nucleosomes is a central molecular step in meiosis.
The next three chapters are concerned with the origin and function of meiosis. The first two of these chapters emphasize that central enzymatic features of meiosis were already present in the prokaryotic ancestors of eukaryotes. One of these chapters went further, indicating that the prokaryotic ancestor was likely able to undergo transformation, a process of DNA transfer between individual bacteria. In transformation, the central proteins catalyzing this process are homologous to proteins with similar functions in meiosis. The other of the first two chapters emphasizes the triggering role of DNA damage in initiating meiosis as well as the purging role of deleterious mutations in diploid-haploid cycles. The major function of meiosis, dealt with extensively in these two chapters, is DNA repair of unavoidable damages in germ line DNA. Especially discussed is the need for meiosis-provided homologous recombinational repair of double-strand breaks and cross-links in the germ line. Both chapters discuss difficulties with earlier proposals that the main selective advantage of meiosis is the long term benefit of producing genetic variation. The third chapter in this section points out characteristics of the eukaryotic cell (such as coding for mRNA capping enzymes and phage-type RNA polymerases in mitochondria) that could have been derived from symbiogenic complex viruses. These characteristics led the author to propose a viral eukaryogenesis theory. By this theory, meiosis is derived from the processes by which a postulated viral ancestor of the nucleus infected new hosts.
The last chapter of the book presents a practical approach to teaching meiosis and gives examples of how a low cost program can be set up. This program will allow students to understand the general processes employed by different types of plants that undergo meiosis. It emphasizes gross morphology and aspects of morphology that can be observed with a hand lens or under a microscope.

Carol Bernstein and Harris Bernstein
Department of Cellular and Molecular Medicine
University of Arizona, USA

CONTENTS : 


I - Molecular Basis of Meiosis .


 1 Intrinsic Homology-Sensing and Assembling Property of Chromatin Fiber 3 Jun-ichi Nishikawa, Yasutoshi Shimooka and Takashi Ohyama


II - Origin and Function of Meiosis .


 2 Meiosis and the Paradox of Sex in Nature 17 Elvira Hörandl

 3 Evolutionary Origin and Adaptive Function of Meiosis 41 Harris Bernstein and Carol Bernstein

 4 Meiosis: Its Origin According to the Viral Eukaryogenesis Theory 77 Philip Bell


III - Teaching Meiosis .


 5 Teaching of Meiosis and Mitosis in Schools of Developing Countries: How to Improve Education with a Plant Reproduction Project 101 Erica Duarte-Silva, Adriano Silvério and Angela M. H. D. Silva .




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