Possible role of DNA synthesis in formation of sister chromatid exchanges

Nature ◽  
1974 ◽  
Vol 252 (5485) ◽  
pp. 739-741 ◽  
Author(s):  
HATAO KATO
Keyword(s):  
Dna Synthesis ◽  
Sister Chromatid ◽  
Sister Chromatid Exchanges ◽  
Chromatid Exchanges

scholarly journals MICROFLUOROMETRIC ANALYSIS OF DEOXYRIBONUCLEIC ACID REPLICATION KINETICS AND SISTER CHROMATID EXCHANGES IN HUMAN CHROMOSOMES

1974 ◽  
Vol 22 (7) ◽  
pp. 478-491 ◽  
Author(s):  
SAMUEL A. LATT
Keyword(s):  
High Resolution ◽  
Dna Synthesis ◽  
Sister Chromatid ◽  
Deoxyribonucleic Acid ◽  
Sister Chromatid Exchanges ◽  
Human Chromosomes ◽  
Metaphase Chromosomes ◽  
Banding Patterns ◽  
Human Leukocytes ◽  
Chromatid Exchanges

Fluorescence of the dye 33258 Hoechst, when bound to chromosomes, is partially quenched by the incorporation of 5-bromodeoxyuridine into chromosomal deoxyribonucleic acid (DNA). This effect allows microfluorometric analysis of DNA synthesis. Metaphase chromosomes from cultured human leukocytes which have incorporated 5-bromodeoxyuridine for a portion of the DNA synthesis period exhibit reduced 33258 Hoechst fluorescence in 5-bromodeoxyuridine-containing regions. Regions synthesizing DNA during a particular interval can thus be highlighted by the appropriate protocol of 5-bromodeoxyuridine administration. Chromosomes from cells which have replicated twice in medium containing 5-bromodeoxyuridine exhibit one brightly and one dully fluorescing chromatid, reflecting incorporation of 5-bromodeoxyuridine into one or two chains of chromatid DNA, respectively. Sister chromatid exchanges, evident as sharply demarcated reciprocal alterations in fluorescence along chromosomes, can be located relative to quinacrine banding patterns. This fluorometric approach should be useful in many instances as a convenient, high resolution alternative to autoradiography.

Saccharomyces cerevisiae rad51 Mutants Are Defective in DNA Damage-Associated Sister Chromatid Exchanges but Exhibit Increased Rates of Homology-Directed Translocations

Genetics ◽  
2001 ◽  
Vol 158 (3) ◽  
pp. 959-972
Author(s):  
Michael Fasullo ◽  
Peter Giallanza ◽  
Zheng Dong ◽  
Cinzia Cera ◽  
Thomas Bennett
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Damage ◽  
Sister Chromatid ◽  
Sister Chromatid Exchanges ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
Dna Damaging Agents ◽  
Break Induced Replication ◽  
Chromatid Exchanges

Abstract Saccharomyces cerevisiae Rad51 is structurally similar to Escherichia coli RecA. We investigated the role of S. cerevisiae RAD51 in DNA damage-associated unequal sister chromatid exchanges (SCEs), translocations, and inversions. The frequency of these rearrangements was measured by monitoring mitotic recombination between two his3 fragments, his3-Δ5′ and his3-Δ3′::HOcs, when positioned on different chromosomes or in tandem and oriented in direct or inverted orientation. Recombination was measured after cells were exposed to chemical agents and radiation and after HO endonuclease digestion at his3-Δ3′::HOcs. Wild-type and rad51 mutant strains showed no difference in the rate of spontaneous SCEs; however, the rate of spontaneous inversions was decreased threefold in the rad51 mutant. The rad51 null mutant was defective in DNA damage-associated SCE when cells were exposed to either radiation or chemical DNA-damaging agents or when HO endonuclease-induced double-strand breaks (DSBs) were directly targeted at his3-Δ3′::HOcs. The defect in DNA damage-associated SCEs in rad51 mutants correlated with an eightfold higher spontaneous level of directed translocations in diploid strains and with a higher level of radiation-associated translocations. We suggest that S. cerevisiae RAD51 facilitates genomic stability by reducing nonreciprocal translocations generated by RAD51-independent break-induced replication (BIR) mechanisms.

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