Cytogenetic and Genome Research

doi: 10.1159/000130293pmid: N/A

Stock, A.D.; Arrighi, F.E.; Stefos, K.

doi: 10.1159/000130294pmid: 4462977

Improved techniques for culturing avian tissue in combination with a trypsinurea chromosome banding technique has allowed an analysis of chromosome homology in three bird species. Three macrochromosomes of the domestic chicken (Galliformes) showed homology with those of the ring-necked dove and the domestic pigeon (Columbiformes). The ring-necked dove and domestic pigeon displayed similar banding patterns, except that the pigeon possessed an additional four pairs of microchromosomes, which are fused to form two pairs of macrochromosomes in the dove. Both G- and C-banded metaphase chromosomes of the three species are presented, and chromosome evolution and phyletic relations are discussed.

Bull, J.J.; Moon, R.G.; Legler, J.M.

doi: 10.1159/000130295pmid: 4462978

Male heterogamety, interpreted as an XX/XY sex-chromosome system, occurs in the turtle genus Staurotypus (family Kinosternidae). Meiotic analysis showed that the basis for the heteromorphism resides in relatively small regions of a pair of macrochromosomes. Heteromorphism was not observed in the three other genera belonging to the same family. Available data for reptiles and higher vertebrates strongly suggest that sex-chromosome heterogamety has evolved independently at least three times in reptiles (in turtles, lizards, and snakes) and, therefore, that the sex chromosomes of birds do not share a common ancestry with those of snakes.

Kajii, T.; Meylan, J.; Mikamo, K.

doi: 10.1159/000130296pmid: 4477981

A family with five successive early abortions and no live births is described. The paternal grandfather and the father have a balanced reciprocal translocation, 46,XY,t(Dq–18q+). Labeling studies of the grandfather’s karyotype have revealed the translocation to involve chromosomes 13 and 18. The last three abortuses were karyotyped and had unbalanced forms of the translocation, each resulting from the segregation of an unbalanced complement: 47,XY,+13q–; 46,XX,13q–; 47,XX,t(13q–;18q+),+18. The role of reciprocal translocation in the causation of recurrent spontaneous abortions is discussed.

Gee, P.A.; Ray, M.; Mohandas, T.; Douglas, G.R.; Palser, H.R.; Richardson, B.J.; Hamerton, J.L.

doi: 10.1159/000130297pmid: 4462979

A mutant Chinese hamster cell line was selected from wild-type CHW cells in 30 µg/ml 8-azaguanine, after exposure for 2 h to 10^–3 M methyl methanesulphonate. This line was subsequently cloned and one clone, isolated in 10 µg/ml 8-azaguanine (CHW-1102), was selected for further study. CHW-1102 showed stability of resistance to 8-azaguanine after six months of growth in nonselective medium and an LD₅₀ to 8-azaguanine of between 10 and 20 µg/ml, compared to 2.5 µg/ml for the wild-type CHW cell line. The doubling time in culture was found to be 13 h, compared to a doubling time of 12 h for CHW. Biochemical studies showed that the mutant cell line CHW-1102 had a specific activity of HPRT of about 1–2 nmol/mg protein per hour compared to a specific activity of the wild type of 200 nmol/mg protein per hour. The spontaneous reversion rate from 8-azaguanine resistance to 8-azaguanine sensitivity was 4.23 × 10–8/locus per generation. Both the parental line (CHW) and the mutant (CHW-1102) have a modal chromosome number of 22 and a relatively stable karyotype. Both lines show some chromosome rearrangement and, in particular, the presence of one long acrocentric marker chromosome, which consists largely of material from chromosomes 6 and 8. Much of the distal part of the long arm of the X chromosome, which is heterochromatic, has been lost in both CHW and CHW-1102. So far as can be determined, no autosomal material, except perhaps the paracentromeric region of chromosome 6, is missing in CHW-1102, although even this material may be represented by a small marker chromosome M₂. Both cell lines show characteristics that are of value for the study of mammalian cell genetics, and CHW-1102 represents a useful addition to the stock of mutant mammalian cell lines.

Norby, D.E.; Hegreberg, G.A.; Thuline, H.C.; Findley, D.

doi: 10.1159/000130298pmid: 4462980

An orange female kitten born to a blue-and-white queen that had been mated to a tortoise-shell torn had a chromosome count of 37 and a karyotype consistent with an XO sex-chromosome constitution. The kitten lived only three days. Co-arctation of the aorta was found. The presence of the XO condition in cats can explain some previously observed exceptions to the sex-linked inheritance of black and orange.

Kim, H.J.; Hsu, L.Y.F.; Hirschhorn, K.

doi: 10.1159/000130299pmid: 4462981

We have studied a family with an X/X translocation which was found in a 16-year-old daughter and in her 34-year-old mother. The daughter had short stature, secondary amenorrhea, and many Turner’s stigmata. The mother, 5-ft tall, had a few Turner’s stigmata and had developed secondary amenorrhea at age 24. Both peripheral leukocyte and skin fibroblast cultures of the daughter revealed, by conventional karyotype analysis, 46 chromosomes with one C-group chromosome missing and with an extra No. 2-like chromosome in all metaphase cells examined. By both Q- and G-banding techniques, this abnormal karyotype was identified as 46,X, + t(X;X)(p22;ql3). An identical translocation chromosome was demonstrated in the mother’s cells, but 50 % of the cells had a 45,X chromosomal constitution. Autoradiographic studies showed that the X/X translocation chromosome was the late-replicating X in all cells examined from both the daughter and the mother. The difference in the phenotypic manifestations of the daughter and of her mother can be explained perhaps by the different contents of the other active X chromosomes. When the same X chromosome is inactivated in all cells, mutations present in the active X chromosome are not compensated and therefore are expressed.

Short, R.V.; Chandley, A.C.; Jones, R.C.; Allen, W.R.

doi: 10.1159/000130300pmid: 4462982

Male and female Przewalski horse/domestic horse hybrids are fertile, unlike all other known interspecific equine hybrids, in which meiosis is almost totally arrested in prophase. In the male Przewalski/horse hybrid (2n = 65) we have shown that a trivalent is formed at the first meiotic division, segregation from which gives two classes of genetically balanced spermatozoa. Both of these are capable of producing normal offspring if they fertilize the eggs of a domestic mare. Chromosome banding studies show a close homology between the karyotypes of the Przewalski horse (2n = 66) and the domestic horse (2n = 64), and it is evident that a single Robert-sonian translocation has occurred, transforming four acrocentric chromosomes of E. przewalskii into two metacentric chromosomes in E. caballus. Thus the parental genetic backgrounds are sufficiently similar to permit normal gametogenesis, with regular segregation from the trivalent of the F₁ hybrid at meiosis. The significance of this is discussed in relation to the evolution of the Equidae.

Bruère, A.N.; Zartman, D.L.; Chapman, H.M.

doi: 10.1159/000130301pmid: 4477982

G-banding of three different Robertsonian translocations of domestic sheep (MI, MII, and MIII) has shown that the arm components of each are nonhomologous. The C-bands of the MI and MIII translocation chromosomes showed heavy blocks of centric heterochromatin which were distributed evenly on either side of the centromeric constriction and which suggested a dicentric structure. The C-band pattern of the MII translocation was regularly exocentric, suggesting that it may be formed by reciprocal translocation. The need for caution on the use of the term “Robertsonian translocation” is discussed. The amounts of centromeric heterochromatin in each of the translocation chromosomes is apparently greater than in the regular metacentrics, which suggests that they are of a more recent origin.