Chromosomes Morphology

Outlined in this section will be the method of Maruyama et al. (12), who were successful in observing metaphase chromosomes inmeristem-atic cells of Vida faba when the fixation of freeze-fractured roots was performed after incubation in buffer solutions. The method allows for experimental studies on chromosome morphology. In fact, the published report also gives the effects of divalent cations on chromosome morphology. 

Grossman, A.I. and Cain, G.D. (1981) Karyotypes and chromosome morphologies of Megalodiscus temper-atus and Philophthalamus gralli. Journal of Helminthology 55, 71-78. 

HOMOLOGOUS CHROMOSOMES Chromosomes occurring in pairs, one derived from each of two parents, normally (except for sex chromosomes) morphologically alike and bearing the same gene loci each member of such a pair is the homologue of the other. 

II associates with chromatin before nuclear envelop breakdown (40). By cytological examination, chromosome-bound condensin I and condensin II do not overlap (36). Depletion of condensin I or condensin II causes distinct abnormalities in chromosome morphology (41), suggesting that the two complexes may not be functionally redundant. 

The use of NaOH as the denaturation solution is preferred to other methods, because the quality of interphase cell and chromosome morphology is not significantly damaged by this method. It is important, however, to make the NaOH stock solutions fresh for each denaturation. 

Chromosome morphology. Chromosomes become visible under the light microscope only at certain phases of the nuclear division cycle. Each chromosome in the genome can usually be distinguished from the others by such features as (1) relative length of the whole chromosome (2) the position of the centromere, a stmcture which divides the chromosome into a crosslike structure with two pairs of arms of different length (3) the presence of knobs of chromatin called chromomeres, and (4) the presence of small terminal extensions called satellites. (See Fig. 1-11.)... 

Goodpasture, C.E., and RE. Arrighi. 1976. Effects of food seasonings on cell cycle and chromosome morphology of mammalian cells in vitro with special reference to turmeric. Food Cos. Toxicol. 14(1) 9. 

Stubblefield, E. (1964), DNA synthesis and chromosomal morphology of Chinese hamster cells cultured in media containing N-deacetyl-N-methyl-colchicine (colcemide), in "Cytogenetics of Cells in Culture" (R. J. C. Harris, ed.) Academic Press, New York. 

Bui HT, Van Thuan N, Kishigami S, Wakayama S, Hikichi T, Ohta H, Mizutani E, Yamaoka E, Wakayama T, Miyano T. 2007. Regulation of chromatin and chromosome morphology by histone H3 modifications in pig oocytes. Reproduction 133(2) 371-382. 

Edema, N.E. and Okoloko, G.E. (1997) Effects of the water soluble fraction of Escravos light and Odidi well crude oils on root growth, mitotic cell division and chromosome morphology ot Allium cepa L. Bulletin of Science Association of Nigeria. 21,15-18... 

Morgenstern, E.K. 1962. Note on chromosome morphology in Picea rubens Sarg. and Picea mariana (MUl.) B.S.V. Silvae Genet. 11 163-164. 

Kato, Y.T.A. 1984. Chromosome morphology and the origin of maize and its races. Evol. Biol. 17 219. 

Depending on the experimental purpose, aceto-orcein squashes can be prepared by three different experimental regimes, which are summarized in Protocol 1.1. First, dissected brains can be squashed in aceto-orcein without colchicine treatment and hypotonic shock (i.e.. Protocol 1.1, with the omission of steps 3 and 4). This procedure allows observation of all phases of mitosis and permits evaluation of the mitotic index and the frequency of anaphases (Gatti and Baker 1989). However, chromosome morphology is poorly defined in these preparations. 

The methanol/acetic acid fixation techniques described above preserve chromosome morphology very well, but they remove a substantial fraction of chromosomal proteins. Thus, preparations obtained by these techniques are not suitable for immunolocalization of proteinaceous components of metaphase chromosomes. We have therefore developed a series of fixation procedures that result in good chromosomal quality with minimal removal of proteins. We stress here that different fixation protocols result in differential extraction of chromosomal proteins. Thus, for each protein under study, develop a fixation procedure that minimizes its removal from the chromosomes. In addition, we have... 

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