Graduate Thesis Or Dissertation
 

Influence of chelating agents on cytological exchanges and genetic recombination in Zea mays L.

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2z10wv37d

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  • The present investigation with the chromosomes of Zea mays was conducted to determine: (1) the effects of chelating agents on the process of cytological exchange, and (2) the effects of chelating agents on genetic recombination. To ascertain the influence of chelating agents on cytological exchange, four known heterozygolis paracentric inversion stocks of Zea mays were treated with several concentrations of ethylenediamine tetraacetic acid (EDTA) and dimethyl sulfoxide (DMSO) singly and in combination prior to meiosis. The four chromosomes with known inverted segments were: (1) chromosome two with an inversion involving 19 map units, (2) chromosome three with an inverted segment of 28 map units, (3) chromosome seven with a large inversion in most of the long arm, and (4) chromosome nine with an inverted segment of approximately 33 map units. Pollen mother cells were utilized for chromosome analysis after fixing in Carnoy's solution and staining with propionic carmine. Cytological exchanges produced by the different treatments were measured by counting the number of dicentric bridges and acentric fragments observed in anaphase I and II. Depending upon the concentration used, both EDTA and DMSO singly or in combination were found to produce significant increases in cytological exchanges in the four inversion stocks. Zea mays stocks, heterozygous for four known linkage groups involving seed and seedling characteristics, were treated with EDTA and DMSO and were crossed with untreated homozygous plants by means of hand pollination. The effects of the two chelating agents on genetic recombination were then determined by scoring the progeny from the testcrosses. Genetic recombination in the testcross stocks was significantly increased by EDTA and DMSO, singly or in combination, in all the testcrosses. In some instances genetic recombination and cytological exchange were both increased significantly in the same chromosome, whereas in other cases no such relationship was observed. The study may provide valuable clues as to the specific effects that chelating agents exert on genetic recombination and cytological exchange. Furthermore, through the utilization of both cytological and genetic techniques, a better understanding of the entire process of crossing over may be obtained.
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