Intensity heteromorphisms of human chromosome 15p by DA/DAPI technique

Summary We suggest that the short arms of human chromosome 15 (15p) exhibit intensity heteromorphisms by DA/DAPI technique. A method for classification of variable intensities is proposed. The different intensities can be classified into at least five classes. They are: negative, pale, medium, intense, and brilliant. Therefore we suggest that 15p is not always positive by DA/DAPI technique. The present findings reveal that the heteromorphism on 15p is far greater than previously thought.     

DA/DAPI fluorescent bands in the chromosomes of Pan paniscus

The fluorochrome pattern produced by DA/DAPI double staining in Pan paniscus chromosomes is reported. The location of DA/DAPI prominent bands differs from that reported for all other hominoid species. However, the pattern in the pygmy chimpanzee is most similar to that seen in Pan troglodytes. Comparison of the DA/DAPI pattern of the other hominoid species allows the construction of a proposed hominoid ancestral karyotype and a preliminary phylogenetic reconstruction of DA/DAPI bands for the great apes and man.     

Satellite DNA sequences in the human acrocentric chromosomes: information from translocations and heteromorphisms.

Satellite III DNA has been located by in situ hybridization in chromosomes 1, 3--5, 7, 9, 10, 13--18, 20--22, and Y and ribosomal DNA (rDNA) in the acrocentric chromosomes 13--15, 21, and 22. In the acrocentric chromosomes, the satellite DNA is located in the short arm. Here we report comparisons by in situ hybridization of the amount of satellite DNA in Robertsonian translocation and "normal variant" chromosomes with that in their homologs. In almost all dicentric Robertsonian translocations, the amount of satellite DNA is less than that in the normal homologs, but it is rarely completely absent, indicating that satellite DNA is located between the centromere and the nucleolus organizer region (NOR) and that the breakpoints are within the satellite DNA. The amount of satellite DNA shows a range of variation in "normal" chromosomes, and this is still more extreme in "normal variant" chromosomes, those with large short arm (p+ or ph+) generally having more satellite DNA than those with small short arms (p- or ph-). The cytological satellites are heterogeneous in DNA content; some contain satellite DNA, others apparently do not, and the satellite DNA content is not related to the size or intensity of fluorescence of the satellites. The significance of these variations for the putative functions of satellite DNA is discussed.     

Population heteromorphisms of Ag-stained nucleolus organizer regions (NORs) in the acrocentric chromosomes of East Indians

Summary The nucleolar organizer regions (NORs) of acrocentric chromosomes in 70 normal East Indians were examined by Ag-staining (NSG) and acridine orange reverse banding (RFA) techniques. The Ag-stainability of NORs was variable from one individual to another but characteristics were constant within each individual. The average modal number of Agpositive NORs per individual was eight. A racial difference in the expression of NORs is suggested. to study the heteromorphism of NORs, the NSG technique was found to be more useful than RFA. Furthermore, it is concluded that there is no direct relationship between a heteromorphism of NORs identified by NSG and that identified by the RFA technique. Quantitative data on these differences is provided. In addition NOR-regions are classified into five sizes namely; very large, large, medium, small, and very small using subjectively defined criteria.     

Non-random participation of chromosomes 13, 14 and 15 in acrocentric associations

Summary The patterns of association of chromosomes 13, 14 and 15 have been examined in a sample of 23 normal individuals. Significant deviations from the expectation of equality of participation have been detected in many of the individuals studied. The implications of the findings in terms of the aetiology of chromosome abnormality in the D group have been discussed.     

rDNA and acrocentric chromosomes in man

Summary A malformed female infant was found to have a 46,XX complement with a chromosome 8 shorter than normal with a secondary constriction and satellites on the short arm. Chromosome studies on the clinically normal father showed a balanced translocation between chromosome 8 and 13, i.e., 46,XY,t(8;13) (p21 p12). The proposita, carrier of the unbalanced form of the translocation, resulted partially monosomic for short arm of chromosome 8 (8p-) and partially trisomic for short arm of chromosome 13.The levels of DNA complementary to rRNA (normal in the father who had 10 NOR and increased in the proposita who had 11 NOR) confirmed our interpretation of the rearrangement.     

Ribosomal cistrons and acrocentric chromosomes in man

Summary DNA derived from patients with trisomy 21, from probands with a normal karyotype, and from donors with the karyotype 45XXD-G-t(DqGq)+ was hybridized with labeled (18s+28s) ribosomal RNA from HeLa cells. The saturation plateaus obtained with DNA of five of the six patients with trisomy 21 tested reveal the presence of increased numbers of ribosomal cistrons. Quantitatively the increase exceeds the expected amount (10%) in two of these five patients. One patient was found to have a normal saturation value.Two of four translocation carriers D/G showed significantly lower saturation plateaus than persons with a normal karyotype, suggesting the loss of rDNA upon formation of the translocation chromosome in some but not in all cases of this chromosomal constitution.

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Zusammenfassung Die DNA von Patienten mit Trisomie 21, von gesunden Probanden mit normalem Karyotyp und von Spendern mit dem Karyotyp 45XXD-G-t(DqGq)+ wurde mit markierter (18s+28s) ribosomaler RNA aus HeLa-Zellen hybridisiert. Bei 5 der 6 untersuchten Patienten mit Trisomie 21 fanden sich erhöhte Sättigungs-Plateaus, die das Vorhandensein einer gegenüber der Norm erhöhten Anzahl ribosomaler Gene anzeigen. Bei 2 dieser Patienten übersteigt der Überschuß an rDNA den Erwartungswert von 10%.Ein Patient mit Trisomie 21 zeigte normale Sättigungswerte. 2 von 4 untersuchten Translokationsträgern (D/G) hatten signifikant erniedrigte Sättigungswerte, während die anderen 2 Probanden im Normbereich lagen. Dieser Befund weist darauf hin, daß es bei der Bildung des Translokations-Chromosoms in manchen Fällen zum Verlust von nucleolusorganisierendem Material kommt.

     

Chromosome heteromorphisms in the gorilla karyotype. Analyses with distamycin A/DAPI, quinacrine and 5-azacytidine

The chromosomes of one male and three female gorillas were extensively studied with various regional banding methods. The chromosomes were stained with the fluorescent dyes quinacrine mustard and distamycin A/DAPI (DA/DAPI), which label different subsets of heterochromatin in the chromosome complement. Furthermore, lymphocyte cultures were treated with the cytidine analog 5-azacytidine (5-azaC). The 5-azaC-induced undercondensations were found in most of the DA/DAPI-bands as well as in many telomeric C-bands. The karyotype of the gorilla exhibits a considerable number of heterochromatin variants. Of the different types of heteromorphisms noted, the most striking is that involving the short arm regions of chromosomes 12 to 16 and 23 (satellite stalk regions) and the paracentromeric heterochromatin of chromosomes 17 and 18. There also are numerous heteromorphic C-bands localized in the telomeric regions of homologous chromosome arms. In comparison, only few heteromorphisms occur between C-bands in the centromeric and pericentromeric regions of homologs. Finally, a variability in the fluorescence intensity of quinacrine-bright satellites in the short arms of chromosomes 12 to 16, 22, and 23 is observed.     

Polymorphism of 5-methylcytosine-rich DNA in human acrocentric chromosomes

Summary The acrocentric chromosomes of 18 unrelated individuals were analyzed by sequential staining by the chromomycin A₃/methyl green R-banding technique to identify the chromosomes, followed by an indirect immunoperoxidase technique to detect 5-methylcytosine (5MeC)-rich DNA. The short arms of both chromosomes 15 usually (92% of the chromosomes) had a large collection of 5MeC-rich DNA, which was always rich in AT base pairs. Much less commonly (11% of the possible occasions), a collection of 5MeC-rich DNA was seen on the short arm of a chromosome 13, 14, 21 or 22, and this DNA was always rich in GC base pairs. Sequential distamycin A/DAPI (DA/DAPI) and R-banding studies were carried out in 13 of these 18 individuals. There was bright DA/DAPI fluorescence of the 5MeC-rich region on the short arm of chromosome 15 but not on that of any other acrocentric chromosome. One implication of these findings is that bisatellited or other abnormal chromosomes that are DA/DAPI negative and 5MeC positive cannot be derived from number 15. In the case of a de novo chromosome of this type, the specific origin from any other acrocentric chromosome could be demonstrated by examining 5MeC-binding of the parental chromosomes.