Satellite DNA loss and nucleolar organiser activity in an individual with a de novo chromosome 13,14 translocation

Abstract

The distribution of satellite DNA and nucleolar organizer activity were studied in a female with a new dicentric translocation chromosome derived from the maternal chromosomes 13 and 14. More than half the satellite DNA (60.5%) was lost in the translocation, together with both nucleolar organizer regions (NOR). At least 1 NOR (chromosome 21) which was inactive in the mother (by the AgI reaction) is active in the subject, and this may be an example of functional compensation. The somatic cells of the mother of the subject, which do not have the translocation, show a high frequency of acrocentric associations, but these do not include any obvious excess of associations involving chromosomes 13 and 14, indicating that the high frequency of association in somatic cells is not in itself a predisposition to Robertsonian translocation in germ line cells. The father''s chromosomes 9 both have more satellite DNA in the secondary constriction than normal, but this is not reflected in any obviously larger size of the C[constitutive heterochromatin]-band in this region.