[Trisomy 4p. Three new observations (author's transl)]

Three new observations of trisomy 4p are reported. Two are due to a maternal translocation t(4;15). The third is due to a "mirror" duplication, it is the first case of trisomy 4p without balanced parental rearrangement. The very characteristic phenotype is compared to that of 13 other patients already reported in the literature.

[Chromosome analyses in parents of children with trisomy 21[]

In connection with a comparative study between parents of trisomic 21 children and control parents, the authors discuss the eventual role of the increase of association rates between acrocentric chromosomes on the appearance of non-disjunctions and translocations affecting chromosome 21. The results are analyzed and compared with data found in the literature.

[Epidemiological aspects of trisomy 21]

The authors analyse cytogenetic and epidemiological data of 4760 cases of trisomy 21 found in 22 European Centres of Genetics. This cytogenetic study is dealing with the frequency of regular free trisomies and those in mosaics and of trisomies by translocation. The frequency of the different types of translocation has been established thanks to an identification of the chromosomes through marking techniques. The risks and causes of recurrence are discussed. From the epidemiological aspect, the role of the mother's age was the subject of a special study which confirms the bimodal distribution of the trisomy 21. This distribution is discussed in association with the other epidemiological factors: X-ray, virus, auto-immunity and gynaecological disorders.

[Partial trisomy 11q and familial translocation 11--22 (author's transl)]

By heat denaturation, a reciprocal translocation was found in the mother of two malformed sibs. In her 46,XX,t(11 ;22)(q23 ;q11) caryotype, the rearranged elements exhibit no change of length. The 2 sibs are trisomic for the distal part of the long arm of chromosome 11.

[Trisomy 8 in mosaicism]

Case report of a 6 year old girl without clear dysmorphism or mental deficiency. Chromosome studies, performed on blood lymphocytes, showed trisomy 8 in 80 % of the cells. This case is discussed with regards to a short literature analysis.