Increased rates of telomeric recombination and pericentromeric instability in the alternative pathway of telomere lengthening (ALT) generate neoacrocentric minute chromosomes. Human ALT minute chromosomes are two to five times smaller in size than chromosome 21 and bear centromeric and telomeric repeats. Multicolor FISH in a pseudocolored metaphase spread from the ALT U2-OS cell line shows that minute chromosomes also carry genomic DNA. These autonomous DNA entities can provide important information for the function of normal and cancer genome and could be exploited as putative nonintegrating large-scale cloning vectors for gene therapy. For details, see the article by Gagos and colleagues on page 8146 of this issue.

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