The XY body: a specialized meiotic chromatin domain.

The sex chromosomes of mammalian spermatocytes form a specialized nuclear territory known as the XY body, where both transcription and homologous recombination are restricted. The array of proteins assembled into the XY body is typical of heterochromatin. This special subnuclear domain is in distinct contrast to the autosomal domain of the spermatocyte nucleus, where both homologous recombination and transcription occur. The special features of the XY body might reflect absence of homology between the sex chromosomes, rather than any form of dosage compensation, and may also serve to mark parental origin of the paternal X chromosome.