The relation of meiosis and mitosis
C. H. Waddington in An Introduction to Modern Genetics, 1950
Fig. 54. Th e Relation of M itosis and Meiosis (according to Darlington).—The stages of mitosis are shown on the left, and the corresponding stages of meiosis on the right. Note that the chromosomes are double at their first appearance in mitosis, but not in the earliest (leptotene) stage of meiotic prophase. They pair in zygotene, beginning to become double (split) in pachytene, and are double in the last stages of meiotic prophase (diplotene and diakinesis). In mitosis anaphase begins by the division of the centromeres, but in meiosis this does not occur till the anaphase of the second division (not shown).
Mitosis and the Cell Cyc le
Murray Brookes, Anthony Zietman in Clinical Embryology, 1998
Cell proliferation is dependent on a complexprocess of cell division known as mitosis, compris ing karyokinesis (nuclear division) and cytokinesis (division of cell cytoplasm). It is the only event in the life cycle of a cell readily distinguishable in the light microscope. Chromatin, composed of gene-bearing DNA, is dispersed in the nucleoplasm at rest. The chro mosomes become visible in early mitosis as discrete threads of condensed chromatin. There are 22 num bered pairs of autosomes, i.e. homologous chromosomes in human cells; plus two sex chromosomes, either XY in males, or XX in females (Figures la, b, c).
Chromosomal abnormalities and structural variants
Tom Strachan, Andrew P Read in Human Molecular Genetics, 2018
Human chromosomes have been analyzed for research and diagnostic purposes for over 50 years. Chromosome structure and behavior are relevant in both mitosis and meiosis. However, when human chromosomes are studied under the microscope it is almost always during mitosis. The introduction of techniques that revealed chromosome banding patterns allowed each individual chromosome to be identified, and permitted more accurate definition of chromosomal abnormalities. Chromosomal abnormalities too small to be seen under the microscope were long suspected to be the cause of a number of unexplained recurrent syndromes and also of many individual cases in which a patient had a unique pattern of abnormalities. This chapter describes a range of abnormalities involving wrong numbers or structures of chromosomes or that, like gene conversion, are produced by essentially chromosomal mechanisms. It also describes genetic abnormalities that affect the phenotype of a person.
Poly(ADP-ribosyl)ation is recognized by ECT2 during mitosis
Published in Cell Cycle, 2014
Mo Li, Chunjing Bian, Xiaochun Yu
Poly(ADP-ribosyl)ation is an unique posttranslational modification and required for spindle assembly and function during mitosis. However, the molecular mechanism of poly(ADP-ribose) (PAR) in mitosis remains elusive. Here, we show the evidence that PAR is recognized by ECT2, a key guanine nucleotide exchange factor in mitosis. The BRCT domain of ECT2 directly binds to PAR both in vitro and in vivo. We further found that α-tubulin is PARylated during mitosis. PARylation of α-tubulin is recognized by ECT2 and recruits ECT2 to mitotic spindle for completing mitosis. Taken together, our study reveals a novel mechanism by which PAR regulates mitosis.
Sulla Terminologia dei Processi Mitotici
Published in Giornale botanico italiano, 1947
Summary The Author has proposed to establish a general plan for the best known modality of the mitosis discovered in these last years in the higher organism animals and vegetables. Two facts are taken in consideration: the distribution of the chromosomes in the anaphase and the chromosome structure. When the distribution of the chromosomes is unever, the mitosis is called with the phrase “mitosis with irregular distribution” (case of the distribution of the chromosomes non regular between the two poles), or “restitutional mitosis” (case of the forming of the restitution nucleus in metaphase or in the anaphase), or “endorestitutional mitosis” (case of the return of the resting stage before the end of the prophase). A special case is given when is present the accessory phenomenon of the somatic pairing, in which case the mitosis is called precisely “mitosis with somatic pairing”. The Author regards to the mechanism of the mitosis, observes that the determination of the structure gone beyond the chromatid has not value because the anaphase distributes as a rule whole chromatids. From this point of view the types of chromosomes experimentally observed in an undoubted manner are exactly: monochromosomes, diplochromosomes, polychromosomes, univalents, bivalents, polivalents, diplounivalents and diplobivalents. These two last types of the chromosomes are observed during the first mitosis of the spore, in cases in which the meiosis respectively fails in the interkinesis or before the heterotypic anaphase. The term diplounivalent is originated by the author to distinguish this type of chromosome (that though present in the mitosis is however of meiotic origin) from the other type (the diplochromosome) that has same structure but not of meiotic origin. (The diplochromosome is owing to a supernumerary reproduction of the usual mitotic chromosome). It is also describes, as far as it can be said accuracy, the course of the different types in metaphase and in anaphase. Keeping thus in mind the chromosome structure (the chromatid is considered as a unity) the mitosis is subdivided in the following types: 1° Mitosis with monochromosomes; 2° Mitosis with diplochromosomes; 3° Mitosis with polychromosomes; 4° Mitosis with diplounivalents; 5° Mitosis with diplobivalents. The terms proposed considering the chromosome distribution or the chromosome structure can be combinable so that the mitosis with monocromosomes (etc). can be called “restitutional mitosis with monochromosomes” (as for instance in the case of the action of the colchicine), or endorestitutional mitosis with monochromosomes (as for istance in the case of the tapetal cells of Spinacia). Not adding either the term restitutional or endorestitutional, it is understood that the course of the mitosis is regular right up to the end. In the course of his research the Autor shows a personal explanation for the “later divisions ” in Culex (Berger 1938, Grell 1946) and points out the necessarity of new researches on the mitotic, supramitotic, etc. chromosomes type of Trillium (Matssuura e Haga 1940).
Mitosis and mitotic activity in Codium fragile (Suringar) Hariot (Chlorophyceae)
Published in Phycologia, 1969
Carol Ann Borden, Janet R. Stein
The mitotic cycle and periodicity of mitosis in Codium fragile in culture were investigated, primarily using germlings. In most respects mitosis resembles “normal” mitosis. However, a persistent nucleolus-like body was observed during all stages of division using acetocarmine stain. Attempts to ascertain the chemical nature of this body were unsuccessful. Experiments on the periodicity of mitosis disclosed a series of peaks of mitotic activity which appear unrelated to the time of onset of the light or dark period. Mitosis within any one germling is asynchronous.