▪ Abstract Here we review the biology of early generation neopolyploids and discuss the profound changes that accompany their formation. Newly formed auto- and allopolyploids exhibit considerable meiotic complexity, including multivalent pairing, multisomic inheritance, and the production of unbalanced gametes. The cytogenetic behavior of allopolyploids and autopolyploids differ statistically, but are more similar than commonly believed. The progeny of neopolyploids include a high frequency of aneuploids, pseudoeuploids and homeologue-recombinant genotypes that may contribute to the phenotypic variability observed in early generation polyploids. We find no evidence to support the traditional view that autopolyploids possess lower fertility than allopolyploids, casting doubt on the paradigm that allopolyploids should be more frequent due to their inherent fertility. The fertility of early generation polyploids increases rapidly, owing largely to selection against meiotic configurations that generate unbala...

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Neopolyploidy in flowering plants

CONTENTS INTRODUCTION ... ..... ... .. 54 Cross-Specific Comparisons 55 LOWER EUCARYOTES .... 57 Criteria for Mutant Isolation 57 Fertility 57 Effects on specific meiotic events 58 Mitotic disturbances 58 Yeasts 59 Fertility mutants ........ ... ... 60 Mutants with altered meiotic exchange .. ...... 62 Defective mating-type control of sporulation 63

The genetic control of meiosis.

Publisher Summary This chapter discusses the genetic variation in chromosome pairing Alterations in the behavior of chromosomes at meiosis are known to result from genetic variation as well as from differences in several environmental factors The operation of selection on genetically controlled variation in the chromosomal phenotype is responsible for the development of meiotic mechanisms adapted to the requirements of the breeding structures of species and of their populations The fertility of an organism and consequently the fitness of the lineage to which it belongs are intimately related in sexual forms and in some apomicts, to the efficiency of the over-all meiotic process The prime function, upon which the efficacy of the process depends, is the segregation of homologous chromosomes Two distinct aspects of the process of meiotic chromosome pairing are therefore under genetic control The extent to which synapsis is realized within the chromosome complement is determined by the activities of major genes and polygenes and by interactions within the genetic system comprised of relevant genes of both kinds The specificity of synapsis is widened or narrowed by gene action to permit the pairing of chromosomes distantly or closely related genetically and evolutionarily

Genetic Variation in Chromosome Pairing

Publisher Summary This chapter discusses the cytology of coccids. The evolution of cytological mechanisms within the group and the bearing of the data on coccid systematic are briefly discussed. Only nuclear or chromosomal cytology is considered. The data of coccid cytology discussed is in reference to the analysis of the diverse mechanisms evolved in various groups. Their bearing on general cytological problems other than mitosis and sex determination has been only incidentally indicated. In structure and behavior, the salient features of the coccid chromosome stem directly from the diffuse nature of the kinetochore. The kinetic functions are a property of the chromosome as a whole and are not, as in most organisms, restricted to a specialized zone or organelle. Structurally this is evident in the absence of tall stages of the chromosome cycle of any primary constriction or localized kinetochore. In mitosis, the diffuse kinetochore results in distinctive types of orientation at metaphase, mode of formation of chromosomal fibers, and anaphase disjunction, and the potentiality realized to varying degrees in different tissues and species of complete spatial separation of the constituent chromonematal strands of the chromosome.

Cytology of coccids (Coccoïdea-Homoptera).

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-5223.1951.tb02891.x

The mechanism of co-orientation in bivalents and multivalents. The theory of orientation by pulling

Studies of asynapsis in rye

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-5223.1941.tb03261.x

Chromosomal aberrations in rye populations

The mode of chromosome pairing in phleum twins with 63 chromosomes and its cytogenetic consequences

A meiotic peculiarity in rye, simulating a terminal centromere

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-5223.1944.tb03310.x

R. Prakken

Papers

Studies of asynapsis in rye

Chromosomal aberrations in rye populations

The mode of chromosome pairing in phleum twins with 63 chromosomes and its cytogenetic consequences

A meiotic peculiarity in rye, simulating a terminal centromere

Contributions to the genetics and cytology of mirabilis