Presumptive monosomy for chromosome 21 was found in a male child with multiple malformations and severe psychomotor retardation. Chromosome analyses of cells from blood and skin samples were performed at intervals during the first few years of his life. In preparations stained with nonbanding as well as quinacrine, Giemsa, and reverse acridine orange banding techniques, only one No. 21 chromosome could be detected with no apparent abnormalities of the other chromosomes. The proband’s phenotypically normal father, paternal grandfather, brother, and paternal aunt have a deletion for a short segment of the long arm of a G-group chromosome. Genetic-marker studies allow the exclusion of a number of blood groups as being associated with No. 21. There is inconclusive evidence suggesting that expression of the Duffy blood group, which has been mapped to chromosome 1, may be influenced by genetic information on chromosome 21. This family is of potential value for further gene-mapping studies.
The modal chromosome number of 14 has been confirmed in Marmosa mitis by examining 622 metaphase spreads derived from heart and lung cell cultures as well as from direct bone marrow preparations. Nine adult individuals, seven females and two males, were investigated. Preferential Y chromosome elimination was observed in both males. It was found that four of the seven chromosome pairs could be identified morphologically while Q-banding allowed differentiation of all chromosomes. The ASG technique revealed that one X chromosome was consistently heterochromatic.
SummarySeveral slide preparation procedures were studied in order to render a semiquantitative indication of an optimum technique or techniques, concerning the over-all cytological quality of the chromosome spreads effected by each technique. A method of scoring for karyotypically analyzable spreads is given. It is concluded that one of the techniques (technique D) be utilized for routine karyotypic studies while a combination of two of the techniques (techniques D and E) should be employed for more extensive studies.
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