The Relationship Between Satellite Association and Trisomy 'G'

Abstract

A hypothesis was put forward, based on a personal observation, that there appeared to be an increased frequency of satellite associations between the acrocentric chromosomes in a young parent of a child with trisomy 'G'. It was therefore considered that there might be a predisposition towards trisomy in some families, and that satellite association was a possible factor in the production of such. The literature covering the cytogenetics and technical significance of satellite association, together with the clinical, cytogenetical, and parental age involvement in trisomy 'G', has been reviewed. The design of this investigation was divided into two parts, namely methodological and clinical. In the first part of the study, a standardised technique was developed to provide the lowest frequency of satellite associations and accurate identification of participating chromosomes. Blood samples from thirty-five normal controls were used. A standard cultural method was employed to compare the satellite association frequencies observed in potassium chloride, sodium citrate, and Hanks/water used as hypotonic solutions. Two further experiments were used to evaluate the effect of time and molarity of the hypotonic solutions on satellite association frequency. Hanks/water was used as the hypotonic solution of choice, giving fewer satellite associations per cell. The second part of this investigation dealt with the cytogenetic analysis of eighteen parents of regular Down's infants matched for age with control parents of normal children. The specific identification of the individual chromosomes involved, and the category of associations was recorded in both groups. Application of the results to statistical analysis showed that in certain specific configurations, there was a significant increase in satellite association frequency in parents of Down's infants. The possible role and causes of satellite association are discussed.