No abstract

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.

Chromosomes from a female mouse cell line were identified by Q-banding prior to in situ hybridization with ³H-labeled mouse minor satellite (satellite II) DNA. No cell was found in which every chromosome was labeled, but grain counts showed that every active centromeric region had minor satellite sequences. In the mouse T(10;13)199H translocation, the breakpoint was within the minor satellite array, leaving clusters of minor satellite at the C-bandless active centromere of the 13¹⁰ chromosome and at the interstitial C-band of the 10¹³ chromosome, which is not associated with centromeric activity. In a mouse A9 (L-cell derived) marker chromosome with one terminal and two interstitial C-bands, only the terminal C-band was adjacent to an active centromere, but minor satellite DNA was present at all three sites. Minor satellite DNA was not detected on the Y chromosome, although the presence of a small amount of divergent satellite sequences on this chromosome could not be ruled out.

The H-Y locus is on the short arm of the human Y chromosome in most individuals but on the long arm in at least one of 17 individuals with structural abnormalities of the Y.

Metaphase chromosome preparations of three male and one female Gorilla gorilla were stained to demonstrate quinacrine, Giemsa, centromeric heterochromatin, and, in one case, reverse-Giemsa bands. A standard karyotype is proposed based on chromosome banding pattern, centromeric index, and length. Three types of variation between homologous chromosomes are described: presence or absence of very bright fluorescence of the short arm or satellite region of acrocentric chromosomes, presence or absence of bright quinacrine bands at the distal ends of chromosome arms, and large differences in the size of the heterochromatic region on each of two biarmed chromosomes. At least half the chromosome pairs show polymorphisms of these types. Satellite associations were scored for each animal. In one case the two smallest pairs of chromosomes were preferentially involved in associations.