Before a cell undergoes division, its DNA is replicated and compressed into identical copies of each chromosome inside the cell nucleus. The chromosomes are then segregated during cell division, so that each daughter nucleus receives a complete copy of the genetic material. The stage when chromosomes are segregated and become separated is called anaphase. Normally, each set of chromosomes is pulled with equal force in opposite directions so that each daughter cell receives the same number of chromosomes.
But when the researchers exposed cells in culture to cigarette smoke, they found that the fused chromosomes were being pulled simultaneously from both directions much like a piece of taffy, forming so-called anaphase bridges between its two ends. Eventually, these chromosomes either tear apart, leaving two broken pieces, or if they don't break apart, the abnormal, elongated chromosomes may persist after anaphase is completed. Either way, a major change in the structure of the chromosomes is the end result.
"Others have found the presence of anaphase bridges is correlated with chromosome instability in cancer cells. Because cigarette smoking is linked to oral, larynx, lung, bladder and esophageal cancers, our results showing that cigarette smoke can produce anaphase bridges and destabilize a cell's chromosomes have added significance," said Dr. Saunders.
"The failure of the cell to accurately repair the cigarette smoke condensate-induced double-stranded breaks probably leads to anaphase bridge formation and chromosomal instability," added Li Z. Luo, Ph.D., a graduate student in the department of biological sciences, who will present the data.
According to their results, which also are detailed in an upcoming article in the journal Mutation Research, the development of anaphase bridges and chromosome instability is most likely due to reactive oxyg
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30-Sep-2004