Primary amenorrhea in a black female with duplication and inversion of the secondary constriction regions of chromosome 9

Pericentric inversions. Problems and significance for clinical genetics

A review is given of the incidence, cytogenetics, and biologic relevance of pericentric inversions (pii). In 251 cases in the literature and our patients, 96 different inversion forms with different breakpoints are found. Eighteen of these cases have been observed several times in unrelated families; they are classified as types. The problem of pii in the heterochromatic regions of chromosomes 1 and 9 is especially emphasized and the investigations required are pointed out. The significance of the individual pii is checked with regard to their behavior in meiosis and their phenotypical relevance. An approximately 1:1 segregation is found. Fertility, stillbirth, and rates of abortion are not statistically altered. The gonadal findings available at present in man are reported and commented on. The occurrence of aneusomic recombinants among the live offspring of carriers shows a marked dependence on the length of the relative inversion segments. Since these are distinctly below average in inversion types, they only result in recombinants in exceptional cases. Certain pointers to an above-random common occurrence of other chromosomal aberrations are not found in families with pii. A correlation between pii and clinical symptoms likewise cannot be detected. However, in this connection it is pointed out that trisomic mosaics were observed jointly with pii(9) and pii(22). The review is completed by a brief examination of the literature concerning the significance of pii in evolution.

Human chromosomal heteromorphisms in American blacks. III. Evidence for racial differences in RFA color and QFQ intensity heteromorphisms

One hundred normal American Blacks (B) were studied by sequential QFQ and RFA banding techniques in order to estimate the type and frequency of heteromorphisms. Color heteromorphisms were classified into one of six colors by RFA and intensity variation into one of five levels by QFQ. The data are compared with a previously studied Caucasian population (C). The frequencies of QFQ and RFA heteromorphisms were significantly higher in the Black than in the Caucasian population. No racial difference was noted for chromosome 21 by QFQ, while RFA demonstrated a clear difference. It is concluded that the maximum characterization of racial differences of human chromosomal heteromorphisms was far greater by RFA than with QFQ. The present study suggests differences in QFQ and RFA heteromorphisms among the two races.