Cytogenetic and Genome Research

Deaven, L.L.; Vidal-Rioja, L.; Jett, J.H.; Hsu, T.C.

doi: 10.1159/000130816pmid: 606503

In the genus Peromyscus cells of all species contain 48 chromosomes; however, the fundamental number varies from 56 (P. crinitus, P. boylei) to 96 (P. eremicus). In some cases biarmed chromosomes are the result of pericentric inversions, while in others they are the result of addition of large amounts of constitutive heterochromatin. Flow microfluorometric DNA-per-cell determinations demonstrated that in some species (P. eremicus) the genome is increased by 36 % over the amount of DNA found in most mammalian species. Studies of unique karyotypes with increased amounts of DNA added as constitutive heterochromatin may ultimately help in the elucidation of the mechanisms involved in karyotype evolution and speciation.

Sumner, A.T.

doi: 10.1159/000130817pmid: 75083

A method is proposed for estimating the sizes of polymorphic C-bands of human chromosomes by microdensitometric measurement of the DNA content of whole chromosomes. The method requires measurements of: a chromosome known not to be polymorphic, as a standard against which to normalize all measurements; the polymorphic chromosomes of interest; and a homologous polymorphic chromosome lacking the C-band. In an example studied here, the C-band of chromosome 9 was estimated to contain about 0.0296 pg of DNA.

Malcolm, S.; Williamson, R.; Boyd, E.; Ferguson-Smith, M.A.

doi: 10.1159/000130818pmid: 606504

Yosida, T.H.

doi: 10.1159/000130819pmid: 606505

F₁ hybrids between the Asian type (2n = 42) and Ceylonese type black rats (2n = 40) invariably showed 41 chromosomes, while those between the Oceanian type (2n = 38) and the Ceylonese type usually showed 39 chromosomes. Twelve F₂ hybrids (three litters) were obtained only from the latter combination. Among them, the karyotypes of nine rats were successfully analyzed. They were segregated into the Oceanian type (three rats) and the F₁ type (six rats). No Ceylonese type was obtained. From the results of fertility testing in F₁ hybrids between these three variants, the Oceanian type is assumed to be more closely related to the Ceylonese type than the Asian type. This coincided well with the results of karyotypic evolution of these geographic variants. Among the nine F₂ hybrids examined, one female consistently showed 37 chromosomes with one X chromosome. This XO female appeared to be a normal female and to have been a sporadic natural occurrence.

Benn, P.; Chern, C.J.; Bruns, G.; Craig, I.W.; Croce, C.M.

doi: 10.1159/000130820pmid: 606506

In human fibroblast cultures derived from adults, clones of cells with a common chromosome rearrangement have been widely reported. Cells derived from one of these clones have been used in hybridization experiments using mouse cells to localize the genes for β-glucuronidase and mitochondrial malate dehydrogenase on human chromosome 7. The results of this study indicate that the genes for these isozymes are located on the region pter→q22 of human chromosome 7.

Henderson, A.S.; Warburton, D.W.; Megraw-Ripley, S.M.; Atwood, K.C.

doi: 10.1159/000130821pmid: 414888

Hybridization in situ was used to identify the chromosomes that carry rDNA in representative lower primates, including the baboons, Papio cynocephalus and Papio hamadryas; the colobus monkey, Colobus polykomos; the tree shrew, Tupaia glis; the lemur, Lemur †ulvis; the saki, Pithecia pithecia; the marmoset, Saguinus nigricollis, and the spider monkey, Ateles geoffroyi. The marker chromosome, common to the Cercopithecines studied to date, carries the rDNA in the baboons. Another marker chromosome carries rDNA in a South American species, the spider monkey. A multichromosomal distribution of rDNA was demonstrated in the tree shrew, lemur, saki, and marmoset. None of the rDNA-containing chromosomes in the prosimians and New World monkeys show homology to the chromosomes that carry rDNA in the Hominids, Pongids, or Old World monkeys.

Campbell, C.E.; Worton, R.G.

doi: 10.1159/000130822pmid: 606507

The chromosome replication patterns of the established cell line CHO have been examined and compared with those of normal primary Chinese hamster cells, using the BudR-Hoechst fluorescence technique developed by Latt (1973). The results of this study indicate that the majority of CHO chromosomes replicate normally. There are four clear-cut exceptions to this rule, three of which are most easily explained as undetected or misinterpreted structural rearrangements of the CHO genome. Several other regions may also replicate differently in CHO and normal primary Chinese hamster cells, but uncertainties in the technique do not allow us to confirm this.

doi: 10.1159/000130823pmid: N/A