Identification of the heterochromatic block in CPA 11 on somatic and meiotic cells. (A) C-band staining of a somatic metaphase. CPA 11 chromosomes are clearly identified by black arrows indicating the presence of large terminal heterochromatic blocks. The inset shows one CPA 11 homolog with sequential G-C- banding. Homology with HSA 21 chromosome is marked through brackets. (B) Pachytene spermatocyte showing diminished RNA polymerase staining on two large domains: the XY body (arrow) and the heterochromatin block of CPA 11 (arrowhead). Bar represents 10μm.