[A case of X/X translocation: t(X;X) (q26;p11)]

An eight-year old girl showing a X/X-translocation (45,X/46,Xt(X;X)(q26;p11)) is presented. Besides short stature and congenital heart-anomaly no other phenotypical abnormalities were present. In all cells containing the abnormal X-chromosome, the latter was late labeling as shown by autoradiography and BrdU-labeling.

5-Methylcytosine in heterochromatic regions of chromosomes: chimpanzee and gorilla compared to the human

Fixed metaphase chromosomes of gorilla and chimpanzee were UV-irradiated to produce regions of single-stranded DNA and then treated with antibodies specific for the minor DNA base 5-methylcytosine (5 MeC). An indirect immunofluorescence technique was used to visualize sites of antibody binding. In the gorilla six pairs of autosomes contained major fluorescent regions, indicating localized regions of highly methylated DNA. These corresponded, with the exception of chromosome 19, to the major regions of constitutive heterochromatin as seen by C-banding. The Y chromosome also contained a highly fluorescent region which was located just proximal to the intense Q-band region. In the chimpanzee no comparable concentrations of highly methylated DNA were seen. Smaller regions of intense 5 MeC binding were present on perhaps six chimpanzee chromosomes, including the Y. Five of these corresponded to chromosomes which were highly methylated in the gorilla.--There is diversity among the human, gorilla and chimpanzee in both the size and location of concentrations of 5 MeC, supporting the idea that satellite DNA evolves more rapidly than DNA in the remainder of the chromosome.

Centromeric heterochromatin and comparison of G-banding in cattle, goat, and sheep chromosomes (Bovidae)

In contrast to findings in many other species, the centromeric heterochromatin in cattle, goats, and sheep is unstained when the C-band method of Arrighi and Hsu (1971) is used. However, a modified C-band technique stains the centromeric heterochromatin strongly. This material also stains strongly with an acridine-orange reverse-banding method. The G-band patterns of some of the chromosomes of these three species show striking similarities, suggesting identity. Even some parts of the metacentric chromosomes of sheep, presumably resulting from Robertsonian fusions, can be identified as nearly unchanged chromosomes of the goat or of cattle. Auto-radiographic studies reveal that these centromeric regions replicate their DNA late in the S phase. Both ³H-thymidine and ³H-deoxycytidine are incorporated at these centromeric regions.

Banding patterns in rat chromosomes (Rattus norvegicus)

By means of the Giemsa staining technique described previously, characteristic banding patterns can be made visible in rat chromosomes. All elements of the karyotype can be distinguished. At the centromeric regions of most chromosomes, striking dark spots can be detected. However, these dark regions are much less prominent than in mouse chromosomes. The X chromosome of <i>Rattus norvegicus </i>comprises 5.31% of the homogametic haploid set. The banding patterns of the X chromosomes in man, mouse, and rat are compared. In metaphase plates of <i>R</i>. <i>norvegicus, </i>an association between autosomes No. 3 and No. 11 is frequently observed. This finding could be interpreted like the analogous phenomenon occurring between the nucleolus organizer chromosomes in human cells.