In support of the telomere concept.
The frequency of recovered X-ray-induced (4000R) rearrangements that, in all probability mimic terminal deletions of the X chromosome was only one of, roughly, 10-5 X chromosomes screened for tip deficiencies. Although the single exception looks terminally deleted, it is probably capped by a very short or nonpolytene telomeric segment. It is apparent from these data that the probability of "healing" or stabilization of a terminally deleted X in the zygotic nucleus or developing embryo of Drosophila melanogaster is vanishingly small. The telomeric caps in two obviously interstitial deficiencies that were recovered represent, roughly, 1/500 of the length of a mitotic chromosome. These findings give some indication of the extreme difficulty of detecting short telomeric segments capping either deleted polytene chromosomes or deleted metaphase chromosomes of, for example, humans.
D000818:Animals; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D004331:Drosophila melanogaster / Q000196:embryology / Q000528:radiation effects* / Q000648:ultrastructure; D005260:Female; D006579:Heterozygote; D008297:Male; D008938:Mitosis; D011831:Radiation Genetics; D012730:Sex Chromosomes / Q000528:radiation effects / Q000648:ultrastructure*; D014965:X-Rays