Routine Chromosome Analysis Research Articles

The importance of further cytogenetic and molecular investigation of acrocentric variants: justification by presentation of a case [t(8;14)(q24;p11)

On routine chromosome analysis a moderately retarded 18-year-old man was found to have an unusual short arm on one chromosome 14. With GTL-banding this chromosome showed an enlarged short arm with no evident secondary constriction. Negative CBG-banding of the short arm suggested the possibility of a translocation involving euchromatin. Interpretation of the abnormality as an unbalanced translocation relied on chromosome analysis using GTL-, CBG-, and Ag-NOR-banding of the proband's phenotypically normal mother, who was found to be carrying a balanced translocation involving chromosomes 8 and 14. In situ hybridization of sequences known to map to the short arm of chromosome 14 confirmed the interpretation and established that the breakpoint was within p11. The patient, whose karyotype is 46,XY, -14, +der(14)t(8;14)(q24.1;p11), is trisomic for the terminal end of the long arm of chromosome 8. The patient's clinical features are described and compared with those reported in patients trisomic for this region. This study demonstrates the importance of using a number of different banding techniques in conjunction with in situ hybridization for the investigation of morphologically unusual acrocentric short arm variants seen at routine diagnosis.

Familial pericentric inversion of chromosome 12.

A pericentric inversion in one of the chromosomes 12, found in two families living in the same region, is described. This inversion was detected during routine chromosomal analysis in two separate laboratories. The breakpoints were at 12p112 and 12q13. The inverted segment represented approximately 20% of the length of chromosome 12. Twenty nine descendants of carriers of the inversion were investigated, and the inversion was present in 23 of them. The other six descendants showed a normal karyotype. After correction for sample bias with the single selection scheme, a segregation ratio of 3:1 was estimated, indicating that the inverted chromosome 12 was preferentially transmitted. All the carriers of the inversion were phenotypically normal, without noticeable fertility disturbances.

Simultaneous production of R-bands and either replication patterns or sister chromatid differentiation

The dye triplet chromomycin/methyl green/DAPI and some related dye combinations were applied to bromodeoxyuridine (BrdU)-substituted and non-substituted chromosomes. In both kinds of chromosome preparations, tri-staining followed by observation at pH 7 resulted in well defined R-bands (excitation wavelength 436 nm) and a mixed DA-DAPI/Q-banding pattern (360 nm). Two approaches have given satisfactory expression both of reverse bands and of the differential BrdU-substitution present in metaphase chromosomes: (1) direct tri-staining at pH 7 and mounting of the preparations at pH 11; or (2) pretreatment of the preparations with Hoechst 33258 plus UV and hot buffer followed by tri-staining and mounting at pH 7. These methods should prove useful for routine chromosome analysis and, in combination with BrdU-labelling, in studies of chromosome structure and replication.

High resolution cytogenetic evaluation of couples with recurring fetal wastage.

Both high resolution and routine chromosome analyses were used to study couples with a history of two or more spontaneous abortions in early pregnancy. In the 20 couples studied, two of the women were found to have an inversion. One paracentric inversion, (13)(q13.1q22.3), was apparent on routine analysis. The small pericentric inversion (11)(p11.12q12.3), was only detected by high resolution techniques. Given the low yield and increased cost and effort involved, we do not believe that high resolution studies are justified for screening couples with repeated abortions.

A Total Population Study of Diagnosed Chromosome Abnormalities in Queensland, Australia

Aneuploidy and structural chromosome rearrangements comprise a significant group of abnormalities in the general population. The true incidence of such abnormalities can be obtained by large research studies of consecutive newborns. In practice, the observed incidence of such chromosome abnormalities is obtained by karyotyping subjects who present for clinical reasons. The difference between the observed clinically indicated rates and the assumed rate (by comparison with data from consecutive newborn studies) would allow the estimation of the unrecognised chromosome abnormality load in the general population. The difference between these two rates would provide valuable data concerning the appropriateness of selection techniques for routine chromosome analysis. This paper reports such a study, from Queensland, Australia. A total population 5-year survey (1976-1980) of the diagnosed chromosome abnormalities in this unselected primary population of 2.2 million people is reported. Five hundred and eighty-nine chromosome abnormalities were detected in a consecutive series of 6092 karyotypes performed (9.7%). This figure is significantly lower than that found in most other reported series where case selection for karyotyping is determined by clinical criteria. In this current study the annual diagnostic rate for chromosome abnormalities was 5.41 per 100,000 of the general population. Cumulative frequency histograms for all types of chromosome abnormality, by age, are presented. In current practice, 32% of chromosome abnormalities are not diagnosed until adult life. Fifty percent of cases of chromosome abnormality (of all types) remain undiagnosed by the age of 1 year, in spite of a relatively liberal acceptance rate on the part of laboratories offering routine karyotyping services. It is concluded that a positive diagnostic rate greater than 10%, in routine chromosome laboratories, probably indicates that more than half the true cases of chromosome abnormality in a population are being missed.

A total population study of diagnosed chromosome abnormalities in Queens land, Australia

Aneuploidy and structural chromosome rearrangements comprise a significant group of abnormalities in the general population. The true incidence of such abnormalities can be obtained by large research studies of consecutive newborns. In practice, the observed incidence of such chromosome abnormalities is obtained by karyotyping subjects who present for clinical reasons. The difference between the observed clinically indicated rates and the assumed rate (by comparison with data from consecutive newborn studies) would allow the estimation of the unrecognised chromosome abnormality load in the general population. The difference between these two rates would provide valuable data concerning the appropriateness of selection techniques for routine chromosome analysis. This paper reports such a study, from Queensland, Australia. A total population 5-year survey (1976-1980) of the diagnosed chromosome abnormalities in this unselected primary population of 2.2 million people is reported. Five hundred and eighty-nine chromosome abnormalities were detected in a consecutive series of 6092 karyotypes performed (9.7%). This figure is significantly lower than that found in most other reported series where case selection for karyotyping is determined by clinical criteria. In this current study the annual diagnostic rate for chromosome abnormalities was 5.41 per 100,000 of the general population. Cumulative frequency histograms for all types of chromosome abnormality, by age, are presented. In current practice, 32% of chromosome abnormalities are not diagnosed until adult life. Fifty percent of cases of chromosome abnormality (of all types) remain undiagnosed by the age of 1 year, in spite of a relatively liberal acceptance rate on the part of laboratories offering routine karyotyping services. It is concluded that a positive diagnostic rate greater than 10%, in routine chromosome laboratories, probably indicates that more than half the true cases of chromosome abnormality in a population are being missed.

Indications for chromosome analysis illustrated by a case of ring 22

A child with multiple anomalies and a suggested diagnosis of Hurler's syndrome was studied. Routine chromosome analysis revealed a ring 22. This case illustrates the importance of chromosome analysis in the evaluation of individuals with developmental problems.

A 46,XX,10Q+ chromosome constitution in a girl. Partial long arm duplication or insertional translocation?

A girl with slight psychomotor retardation, microphthalmia, and colobomata of the left eye, a hypotrophy of the right arm and a surnumerary digit on the right hand is described. The routine chromosome analysis and a G-banding analysis revealed an elongated long arm of chromosome 10. An extra light and dark band was present proximally. Both parents had normal chromosomes. While the visual comparison of the abnormal with the normal chromosome 10, did not enable the extra bands of the normal bands q21 and q22 to be distinguished. However, measurements of length, surface area, and relative reflection of the different light and dark bands of the long arm on tracings or directly on the normal and abnormal chromosomes, enabled us to precisely locate the extra bands and to determine that the abnormal chromosome was a result of an insertional translocation. The value of such measurements is discussed.

Giemsa banding of chromosome 1gh+ and linkage analysis.

A four-generation transmission of 1qh+ chromosome was ascertained by routine chromosome analysis of a mildly dysmorphic and retarded 61/2-year-old female. Concordance between synophrys and the 1qh+ marker was the only consistent phenotypic relationship. The variant chromosome did not appear uncoiled, and Giemsa centromeric staining (C-bands) revealed an increased width of the heterochromatin commensurate with the increased length of the long arm. Giemsa banding of the entire chromosome (G-bands) revealed two heterochromatin bands, identical in appearance, in the centromeric region with the remainder of the chromosome showing normal banding. The distribution of Duffy blood groups in the pedigree was consistent with the locus being on chromosome No. 1.

Two different chromosome abnormalities resulting from a translocation carrier father

Summary The importance of differential chromosome stains despite an apparently normal routine chromosome analysis is emphasized by the studies presented here. Trypsin-Giemsa banding revealed a partial trisomy 7 in an 18-month-old girl with failure to thrive, slow development, and multiple physical anomalies. The father was found to be a balanced translocation carrier. Before amniocentesis could be carried out in a succeeding pregnancy, the mother aborted and the fetus was found to be partially monosomic for the No. 7 chromosome.

Identification of D-D translocations in mentally retarded patients.

Routine chromosome analysis of two patients with severe mental retardation revealed two 45,D-,D-,t(DqDq)+karyotypes. With the aid of a Giemsa banding technique the translocation chromosomes were identified as a t(13q14q) and a t(14q15q).

Partial F trisomy associated with familial F/13 translocation detected and identified by parental chromosome studies

Routine chromosome analyses were initially interpreted as normal in 3 siblings with mental retardation and multiple congenital defects. Subsequent investigation showed that their mother is a balanced carrier of an F/13 chromosome translocation which resulted in a partial F trisomy in her 3 affected children. The clinical syndrome is characterized by moderate mental retardation, multiple craniofacial abnormalities (especially prominent cheeks), congenital heart lession, hypotonicity, and a tendency to increased digital arches. This paper emphasizes the need to study parental chromosomes to detect a hidden or small chromosome change in an affected child, especially if more than one child is affected with the same syndrome.

Double monosomy mosaicism (45,X-45, XX,21-) in a retarded child with multiple congenital malformations.

Double monosomy mosaicism was observed in a three-year-old girl who had mental and physical retardation. Routine blood-lymphocyte and bone-marrow chromosome studies showed an apparent 45, X pattern, which was confirmed by autoradiographic studies with tritiated thymidine. Routine and fluorescent chromosome analyses from bilateral skin biopsies revealed a 45,XX,21– karyotype, which was consistent with the positive sex-chromatin pattern in these fibroblasts as well as in the buccal smear and hair-root-sheath cells. Although her clinical features bore some resemblance to patients with Turner’s syndrome and to patients with G monosomy, our patient did not closely fit either of these syndromes.