The Barr body is a looped X chromosome formed by telomere association.

Walker, C L; Cargile, C B; Floy, K M; Delannoy, M; Migeon, B R · Proc Natl Acad Sci U S A · 1991

basic_science · Level V

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Abstract

We examined Barr bodies formed by isodicentric human X chromosomes in cultured human cells and in mouse-human hybrids using confocal microscopy and DNA probes for centromere and subtelomere regions. At interphase, the two ends of these chromosomes are only a micron apart, indicating that these inactive X chromosomes are in a nonlinear configuration. Additional studies of normal X chromosomes reveal the same telomere association for the inactive X but not for the active X chromosome. This nonlinear configuration is maintained during mitosis and in a murine environment.

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