[A rare variant of chromosome 1 in the house mouse: the presence of 2 supernumerary heterochromatin segments].

An abnormal chromosome 1 with two extra interstitial heterochromatin segments was found in the karyotype of a house mouse from the Maritime Territory. Until recently, variants of the abnormal chromosome 1 with the only extra C-block were known in house mouse of some European populations. Sizes of the abnormal chromosome 1 in a house mouse of the Maritime Territory are increased almost by 50%, in comparison with the normal homologue. C-banding showed that extra segments were localized in the area of D and F segments of the standard karyotype in house mouse, and stained homogeneously.