Several studies on aneuploidy and aging have shown a significant incre
ase in the loss of chromosomes in both males and females with age. Oth
ers have observed a significant increase in micronucleus formation in
lymphocytes with age. The objectives of this investigation were to det
ermine the relationship between sex chromosome loss and increased micr
onucleus frequencies with age, to establish sex chromosome loss freque
ncies unbiased by cellular survival factors or slide preparation, and
to determine the effect of smoking on sex chromosome loss. Blood sampl
es were obtained from 8 newborn females and 38 adult females ranging i
n age from 19 to 77. Isolated lymphocytes were cultured according to s
tandard techniques and blocked with cytochalasin B. Two thousand binuc
leated cells per donor were scored using a modified micronucleus assay
to determine the kinetochore status of each micronucleus. Slides were
then hybridized with a 2.0 kb centromeric X chromosome-specific probe
labeled with biotinylated dUTP, and detected with fluorescein-conjuga
ted avidin. All micronucleated cells were relocated and their X chromo
some status was determined. We found the X chromosome to be present in
72.2% of the micronuclei scored; additionally our results show a sign
ificant increase with age in the number of micronuclei containing an X
chromosome.