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

The distribution of satellite DNA and nucleolar organiser activity have been 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 the nucleolar organiser regions (NOR'S). However, at least one 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-band in this region.