bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronology and pattern of human chromosome replication
Authors: Takagi N. , Sandberg A.A.
Published: April 2008

DNA synthesis in diploid human cells was studied at the cellular and chromosomal levels by means of 3H-thymidine labeling and autoradiography. It was observed that the rate of DNA synthesis increased slowly at the beginning and decreased rapidly at the end of the S period, with a peak midway in the period. The rate and duration of DNA synthesis in individual chromosomes were found to be characteristic for each chromosome pair. Even though there is a certain tendency for the longer chromosomes to have a longer S period, enough variation existed to indicate that the structural make-up of the chromosomes may play an important role in the rate and length of time during which chromosomal DNA synthesis occurs.
The chromosomes of Spermophilus townsendi (Rodentia: Sciuridae) and report of a new subspecies
Authors: Nadler C.F.
Published: April 2008

Chromosomes were analyzed from five subspecies of the ground squirrel, Spermophilus townsendi. The diploid chromosome number was 46 in S. t. vigilis and S. t. canus, 38 in S. t. idahoensis and S. t. mollis and 36 in S. t. townsendi. A chromosomally homogenous population of ground squirrels, separated from S. t. townsendi by the Yakima River and having 38 instead of 36 chromosomes, was recognized as a new subspecies, S. townsendi nancyae. Chromosomal evidence linked with zoogeography suggest that the subspecies of S. townsendi radiated from an ancestral population (2n = 46), probably originating in Oregon, with eventual spread north across the Columbia River (S. t. townsendi and nancyae) and southeast into Idaho, Utah and Nevada (S. t. mollis and idahoensis). Robertsonian centric fusion rather than dissociation of metacentric chromosomes receives strong zoogeographic support as the mechanism responsible for karyotype evolution in S. townsendi.
A case of multiple chromosomal rearrangements with persistence of foetal haemoglobin
Authors: Nuzzo Fiorella , Marini A. , Baglioni C. , Ford C.E. , De Carli L. , Piceni Sereni Lucia
Published: April 2008

The karyotype analysis of a mentally retarded baby with persistence of embryonic and foetal haemoglobin showed three abnormal chromosomes. One was identified as a No. 3 with an extra segment, another as No. 6 or 7, or X, with a deletion and the last one was assigned to pair 15 by autoradiography. The parents of the propositus were both haematologically and chromosomally normal. The possible mechanisms of origin of the multiple chromosomal rearrangements arc discussed. The data are also compared with those reported by other authors in connection with different chromosomal abnormalities. Particular attention is paid to trisomy D, which has been found associated with persistence of foetal haemoglobin. Although the possibility of a nonspecific effect of the observed karyotypic alterations cannot be ruled out, the suggestion is made that one or more of the abnormal chromosomes are carriers of gene(s) controlling the synthesis of e and γ chains.
3H-thymidine-induced chromosome aberrations in cultured human leukocytes
Authors: Vig B.K. , Kontras Stella B. , Paddock E.F.
Published: April 2008

Short-term human leukocyte cultures from two individuals with different cytological backgrounds were treated with 3H-thymidine. Gaps, deletions, fragments and translocations were observed. The two cases responded much differently probably owing to differences in genetic background. Using autoradiographic procedures, it was observed that aberrations arise more or less in equal frequency in the synthesizing regions of chromosomes as in regions which had completed DNA synthesis. Gaps are attributed to subchromatid breaks and are randomly located, i.e., not necessarily restricted to late-replicating, heterochromatic regions.
Studies on the male meiosis of Ellobius lutescens Th.
Authors: Castro-Sierra E. , Wolf U.
Published: April 2008

Studies were carried out on the male meiosis of Ellobius lutescens. The testicles of 29 male specimens were used for this purpose. Among 100 pachytene figures, 25 revealed an association between the sex vesicle and an autosomal bivalent of medium size, whereas in 75 figures the sex vesicle appeared as an isolated structure. The importance of this finding in relation to the proposed translocation of a segment of the Y chromosome to an autosome as well as the significance of this event in relation to a mechanism of sex determination in E. lutescens without zygote lethality is discussed.
High frequency of a specific chromosome abnormality in leukocytes of a normal female
Authors: Gooch P.C. , Fischer C.L.
Published: April 2008

A high frequency of spontaneous chromosomal aberrations was found in a phenotypically normal female with no history of either radiation therapy or clinical abnormalities. The aberrations appear to be in a specific chromosome which we identified as a number 10.
Minute Y chromosome in the lizard genus Uta (family Iguanidae)
Authors: Pennock L.A. , Tinkle D.W. , Shaw Margery W.
Published: April 2008

Evidence is presented for an XX/XY sex-determining mechanism in five species of the genus Uta. All species examined have a somatic diploid complement of 12 macrochromosomes and 22 microchromosomes. The Y chromosome is morphologically distinguishable as the smallest microchromosome in the males. It is paired in metaphase I figures with an X chromosome which is two to three times its size. The size of the X chromosome does not distinguish it from other small microchromosomes in the karyotype.
Sex chromatin frequency in buccal mucosal tissue: the normal female population
Authors: Curtis Diana J.
Published: April 2008

A method of recording sex chromatin scores with a reproducibility of ±3% at two standard deviations is described. In 25 clinically normal women (control group) the frequency of sex chromatin was 40.8 ± 2.56%. The sex chromatin frequency in eight pregnant women did not differ significantly from that found in the control group (t31 = 1.54; P > 0.05). The sex chromatin frequency in 20 newborn females was significantly lower than that recorded for the control group (t40 = 10.97; P < 0.001). Regression analysis showed that increasing sex chromatin frequency over the first six days of life was strongly related to the effect of days. Reasons are given for attributing this finding to a difference in the buccal mucosal tissue between the newborns and adult females rather than to the effect of different hormonal levels.
Comments on the “cytologically verified” hybrids between Bufo and Rana, two genera of anuran amphibians
Authors: Bogart J.P. , Blair W.F. , Hubbs C.
Published: April 2008

Kiley and Wohnus (1968) have reported hybrids between Bufo and Rana. We disagree with their conclusion, in part based on the existence of ‘paternal chromosome markers’ in the maternal karyotype.
Hybridization in the rodent genus Meriones
Authors: Lay D.M. , Nadler C.F.
Published: April 2008

Laboratory hybridization has been achieved between two partially sympatric species of jird, Meriones shawi (2n = 44) and M. libycus (2n = 44). The parental karyotypes differ by at least three autosomal rearrangements and a remodeling of the X chromosome. F1 hybrid karyotypes contain a haploid set derived from each parent, and the species origin of four chromosomes, including the X, can be identified. The FI females are fertile, whereas F1 males are infertile owing to completely or markedly diminished spermatogenesis. The F1 females backcrossed with M. shawi males are fertile and produce normal-sized litters with normal sex ratios; male progeny from this cross have normal spermatogenesis and are fertile. The F1 females backcrossed with M. libycus males exhibit reduced fertility, small litters and an absence of male offspring. The taxonomic status of M. shawi and M. libycus is evaluated with respect to the chromosomal and hybridization data, and the isolating mechanisms involved with speciation in Meriones ate considered.
Elimination of XX cells in the testes of heterosexual bovine twins with XX/XY chimerism
Authors: Weiss E. , Hoffmann R.
Published: April 2008

In five heterosexual male bovine twins and three freemartins, all not older than three months, XX/XY chimerism in the blood and gonads has been found. One heterosexual male bovine triplet showed at the age of 18 or 22 months XX/XY chimerism in the blood but not in the testes. In another male co-twin of a freemartin, XX/XY chimerism has been detected in the blood and the testes (at biopsy) at the age of two months. In the same animal, the blood chimerism was still present at the age of 18 months, whereas the chimerism of the testes had vanished at that time. Therefore, it can be concluded that, in the course of time, the XX cells of the testes have been eliminated. This elimination, which possibly occurs in embryonic life, partially explains why male co-twins of freemartins do not have malformations of the genital organs and are fertile. Possibly, the XY cells of the testes have an eliminating influence against neighbouring cells with an XX karyotype. The eliminating effect could be directed at the two active X chromosomes of these germ cells. The hypothesis would also account for the observation that blood lymphocytes with an XX karyotype, which have, according to the Lyon hypothesis, only one active X chromosome, are not eliminated with time.
A 39, X/41, XYY mosaic mouse
Authors: Evans E.P. , Ford C.E. , Searle A.G.
Published: April 2008

A sterile mouse was found to be a chromosomal mosaic with two cell lines, one containing 39 chromosomes, the other 41. Both types were present in approximately equal numbers in the bone marrow, but the 41-chromosome line alone was identified in spermatogonia and spermatocytes. Evidence from chromosome morphology at mitotic metaphase and from spermatocytes at diakinesis and metaphase I identified the two cell-lines as XO and XYY respectively. The alternative possibilities of exclusion of the XO line from the seminiferous elements by chance and by selection are discussed and the latter interpretation favoured. The possibility is raised that the Y chromosome of mammals carries genetic information essential for normal spermatogenesis, as distinct from its established function in embryonic gonadal determination.
Rates of DNA synthesis in heterochromatic and euchromatic segments of the chromosome Complements of two rodents
Authors: Schmid W. , Leppert M.F.
Published: April 2008

In vitro studies were carried out on kidney epithelial cells and fibroblasts of female Microtus agrestis and fibroblasts of male and female Cricetulus griseus. By means of pulse labeling with tritiated thymidine, the duration of DNA synthesis within the S period of the cell cycle was determined for the autosomal ‘euchromatic’ portions of the chromosome complements, for the large and well-defined, structurally heterochromatic segments and for the active and the ‘Lyon-ized’, inactive X portions in the females. (Both species possess composite-type X chromosomes.) Strikingly similar results were found in both species and both types of tissues studied. In partially overlapping sequences DNA synthesis starts first in the autosomal euchromatin and in the active X, later in the inactive X and finally in the structural heterochromatin; it ends in the same order. “While DNA replication in given euchromatic segments takes nearly four hours, it requires less than two hours in the structurally heterochromatic segments. Interestingly, DNA replication was found to take considerably longer in the active than in the inactive X. This indicates that in the functional X chromosomes the rate of DNA synthesis is not dependent on the number of replicons (which must be assumed to be identical) but is accelerated in the genetically inactivated X chromosome.
Cytogenetical analysis of an ovine male pseudohermaphrodite and the possible role of the Y chromosome in cryptorchidism of sheep
Authors: Bruère A.N. , McDonald M.F. , Marshall R.B.
Published: April 2008

A previously unreported type of male pseudohermaphrodite sheep is described. The animal had XY sex chromosomes in all tissues studied and was chromatin negative. It had female external genitalia and undescended testicular gonads, with an histology distinct from that of previously reported sheep intersexes. Its origin could not be explained on the same basis as the more commonly reported female (XX) intersexes seen in man and other domestic animals. Comparison, however, of this sheep with the ovine cryptorchid suggests that the germ-cell aplasia seen in the latter is genetically determined and due to a possible gene locus or loci deletion of the Y chromosome.
Kinetics of two-break aberration production by X-rays in human leukocytes
Authors: Bender M.A. , Barcinski M.A.
Published: April 2008

An attempt was made to confirm the linear dose-effect kinetics reported by H. J. Evans for the production of two-break aberrations in X-irradiated human leukocyte cultures fixed after 52 to 56 h incubation. Although Evans’ experiments were carefully duplicated, the yield of two-break aberrations showed the same essentially dose-square kinetics observed at all fixation times by other workers using different culture methods. Thus Evans’ suggestion that culture technique influences dose-effect kinetics was not confirmed.
Late-replicating Y chromosome in spermatogonia of the Chinese hamster (Cicetulus griseus)
Authors: Fraccaro M. , Gustavsson I. , Hultén Maj , Lindsten J. , Tiepolo L.
Published: April 2008

The Y chromosome of the Chinese hamster is late replicating in spermatogonial mitoses labelled in vivo. During the last two hours of the S phase the long arm of the Y replicates the majority of its DNA. The short arm terminates replication before this. Replication of the long arm of the X takes place earlier in S, whereas the short arm of the X is synchronous with that of the Y. Two small metacentric autosomes are also late replicating, in synchrony with the long arm of the Y. The distinct pattern of late replication of the Y chromosome of spermatogonia is in agreement with our experience with other mammals. The replication patterns of spermatogonia and a morphological study of the XY bivalent in primary spermatocytes indicate that the X and Y chromosomes pair by their short arms.
Established hyperdiploid hematopoietic cell line with a minute marker chromosome persisting both in culture and in the ‘normal’ donor
Authors: Moore G.E. , Fjelde Audrey , Huang C.C.
Published: April 2008

A permanent human lymphoid cell line with 46 normal chromosomes and one minute marker chromosome was established from a normal human female. The abnormal karyotype was also present in a ‘direct’ three-day culture of the buffy coat and in a second permanent cell line derived from a later sampling of the donor’s leukocytes. The abnormality appears to be a persistent feature of the donor’s apparently mosaic karyotype and persists in the oldest culture line as a marker chromosome two years after establishment.
Placental chorangiomata and mental deficiency in a child with 2/15 translocation: 46, XX,t(2q—;15q+)
Authors: Wurster Doris H. , Hoefnagel D. , Benirschke K. , Allen, Jr. F.H.
Published: April 2008

Clinical, cytogenetic and other laboratory studies are reported in a set of dizygous twins, their parents and siblings. The proposita was a girl with profound mental deficiency of unknown cause; she had been born with a placenta showing marked chorangiomatosis. In addition, she was found to have a chromosomal error consisting of a translocation of material of the long arms of a No. 2 chromosome to the long arm of a No. 15 chromosome. Studies of normal marker loci failed to provide evidence that any of them had been lost or inactivated as a consequence of the translocation.
A karyological study of turtles from the Brazilian Amazon Region
Authors: Ayres M. , Sampaio M.M. , Barros R.M.S. , Dias L.B. , Cunha O.R.
Published: April 2008

The karyo types of five turtles of the genus Podocnemis from the Amazon Region of Brazil were determined. Four species, P. cayennensis, P. expansa, P. sextuberculata and P. unifilis have 28 (2n) chromosomes and one, P. dumeriliana, has 26 (2n). No morphologically distinguishable sex chromosomes could be observed. The difference in number in P. dumeriliana can be explained by the occurrence of a centric fusion. The chromosome numbers in this genus are extremely low when compared with the range previously found in Chelonia (2n = 50 to 64).
Karyotypic analyses of the genus Neotoma (Cricetidae, Rodentia)
Authors: Baker R.J. , Mascarello J.T.
Published: April 2008

Examination of 154 specimens representing nine species of the genus Neotoma revealed diploid numbers of 38, 52, 54 and 56. Six species had the diploid number of 52. Extensive polymorphism was found in two species, N. lepida and N. micropus. Chromosomal variation in the subgenus Neotoma was primarily in Fundamental Number and not in diploid number.
The chromosomes of the chamois (tribe Rupicaprini Simpson)
Authors: Gropp A. , Giers D. , Fernandez-Donoso R. , Tiepolo L. , Fraccaro M.
Published: April 2008

Cytogenetic studies of somatic cells in the chamois, belonging to the tribe Rupicaprini of the family Bovidae, revealed a karyotype with 58 acrocentric chromosomes and with one pair of large metacentrics. The fundamental number of 60 and the presence of Robertsonian changes as a dominating mechanism of karyotype variation seem to be characteristic for the tribe Rupicaprini, as they are for some related tribes of the Bovidae, mainly the Caprini.
Robertsonian-type chromosome variation in the tobacco mouse, M. poschiavinus, and in M. poschiavinus × M. musculus hybrids
Authors: Gropp A. , Tettenborn U. , von Lehmann E.
Published: April 2008

Cytogenetic studies were made in dark-colored wild mice, previously described as M. poschiavinus Fatio, 1869. These mice are found only at a single locality, a Swiss high-altitude valley, the Val Poschiavo/Grisons. The karyotype is characterized by the presence of 26 chromosomes, with seven pairs of meta-centrics, five pairs of acrocentric autosomes and the acrocentric sex-chromosomes (2n = 26; N.F. = 40). The F1 resulting from crossbreeds of M. poschiavinus and the laboratory mouse has invariably a somatic set of 33 chromosomes, 7 metacentrics and 26 aerocentrics (2n = 33; N.F. = 40). Meiotic diakinesis figures of the F1 show seven trivalents, five bivalents and one end-to-end-associated X-Y bivalent. M. poschiavinus, M. musculus and their hybrids seem to display an ideal Robertsonian variation. However, there is marked reduction of fertility in the F1 and in subsequent generations. The analysis of meiotic metaphase II in the male leads to the assumption that meiotic nondisjunction and embryonic aneuploidy are a major cause of the reduced fertility. The infrequent and small litters in the hybrid generations probably represent the viable products of only the balanced genetic combinations. The sequence of Robertsonian fusions that have led to the actual karyotypic conditions in M. poschiavinus seems to have built up an effective barrier, providing cytologic isolation of this species and securing its coexistence with M. musculus. The system of chromosomal variation in M. poschiavinus and its hybrids with the laboratory mouse provides an appropriate material for studies of phenotype variation and of genetic control of biochemical markers.
Chromosomes of Peromyscus (Rodentia, Cricetidae)
Authors: Kreizinger Jean D. , Shaw Margery W.
Published: April 2008

A karyotypic and autoradiographic study was undertaken in an effort to identify the Y chromosome in five subspecies of the deer mouse, Peromyscus maniculatus. Three cells from each of seven male animals were analyzed. Although three of the animals were from the same subspecies and two were from the same location, all seven animals had different karyotypes. The existence of large groups of similar chromosomes, more than one heteromorphic pair of chromosomes or cell-to-cell variation within an animal precluded karyotypic identification of a Y in four animals. However, in all seven animals a probable Y could be designated from autoradiography since one chromosome consistently completed DNA replication later than the rest of the complement. The Y as identified by karyotyping corresponded to the latest labeling chromosome in only two animals. Observations are also presented on the proposed X in males.
The somatic chromosomes of the small Indian mongoose: autoradiographic analysis of an unbalanced translocation heterozygote
Authors: Cohen M.M. , Chandra H.S.
Published: April 2008

The somatic karyotype of the small Indian mongoose (Herpesies auropunctatus Hodgson)was investigated and found to contain 2N = 36 in the female (NF = 68) and 2N = 35 in the male (NF = 66). The female specimen studied was a mosaic (approximately 25%) for an unbalanced translocation, which was ascertained through a large submetacentric marker chromosome. Sex-chromatin determinations revealed approximately 30 % of positive cells to contain two sex-chromatin masses. Autoradiographic analysis identified the X chromosome as a medium-sized metacentric element. However, only one arm of the X was late replicating, and in 30% of the cells both X chromosomes showed late-replication patterns of only one arm. No discernable Y chromosome was evident in male cells.
Genetic studies on a minute centric fragment transmitted through three generations
Authors: Hoehn H. , Reinwein H. , Engel W.
Published: April 2008

Karyotypes of six members of a family in three generations consistently exhibited an additional minute centric chromosome. Except for the mentally retarded propositus, the remainder of the family proved to be clinically normal. The early replicating fragment was frequently found to be associated with acrocentric chromosomes and was located peripherally in the majority of metaphase spreads. As compared to similar cases reported by various authors, the chromosomal minute is considered to be genetically inert, and coincidence with certain clinical features is likely to be fortuitous. It is suggested that the fragment represents one counterpart of a centric fusion event, occurring more often in the general population than has been previously assumed owing to lack of phenotypic expression in carrier persons.
Spontaneous aberrations in lampbrush chromosome XI from a specimen of Triturus vulgaris meridionalis (Amphibia, Urodela)
Authors: Mancino G. , Nardi Irma , Barsacchi Giuseppina
Published: April 2008

Comparison between the standard maps of the Triturus vulgaris meridionaiis lampbrush chromosomes and the lampbrush karyotype of an adult female (♀-IX) belonging to the same subspecies revealed the occurrence of two different chromosomal rearrangements in one bivalent of ♀-IX: lampbrush chromosome XI showed, in fact, a paracentric inversion in one homologue and an intercalary deletion in the other one. The same inversion was detected in all oocytes, whereas the deletion was present only in some of them. These rearrangements appeared in a region of the homologues in which chiasmata are not usually formed. The specimen, freshly collected from nature, appeared phenotypically normal and possessed well-developed ovaries. The occurrence of the heterozygous inversion in all oocytes suggests that very likely it has been transmitted to ♀-IX from one of the parents; the occurrence of the deletion in only a few oocytes indicates that it might arise at meiotic prophase I because of difficulties in pairing brought about by the presence of the inversion.
A comparative chromosome study of the North American species of sticklebacks (Teleostei: Gasterosteidae)
Authors: Chen T.-R. , Reisman H.M.
Published: April 2008

The five North American species of the stickleback family Gasterosteidae were studied karyologically. They constitute two diploid-count groups; one with 46 includes Λpeltes quadracus and Culaea inconstans, and the other with 42 consists of Gasterosteus aculeatus, G. wheatlandi and Pungitius pungitius. The common occurrence of a distinctly large submetacentric pair in complements of all five species suggests a monophyletic origin of this character. The consistent presence of three additional large chromosome pairs in all members of the 2n = 42 group suggests their close relationship. Culaea probably possesses the closest karyotype to that of the progenitor of the 2n = 42 group. Apeltes is perhaps an offshoot of, and distantly related to, their common ancestor. The phylogenetic scheme constructed from the karyological data agrees with that constructed from grosmorphological and behavioral characters. The possible routes of chromosome evolution among the species and genera are discussed. Although pericentric inversions or reciprocal translocation or both might have achieved specific and generic differences, centric fusions or tandem translocations or both are required to separate the 2n = 46 group from the 2n = 42 group. Both the female Apeltes quadracus and the male Gasterosteus wheatlandi had a heteromorphic pair that was not detectable in the karyotype of the opposite sex. This may indicate a probable occurrence of cytologically expressed heterogamety in these two species.
Chronology and pattern of human chromosome replication
Authors: Hossfeld D.K. , Ikeuchi T. , Sandberg A.A.
Published: April 2008

An abnormal subtelocentric, satellited chromosome which was found in a patient with chronic lymphocytic leukemia and in 50% of his family members was studied autoradiographically. It was demonstrated that this chromosome is an altered chromosome 13 with elongated short arms. The theories as to the origin of the extra chromatin were discussed in the light of the autoradiographic results. Some evidence is presented that other chromosomes of the D group may be involved in a similar anomaly.
Chromosomal rearrangements in three generations of a Jamaican family
Authors: Martin Patricia A. , Thorburn Marigold J. , McNeil Smith-Read Elaine H.
Published: April 2008

Chromosomal rearrangements are described in a three-generation family whose members were all normal but for the propositus, who had phenotypic abnormalities suggestive of Patau’s syndrome. The rearrangements appeared to involve chromosomes of the D and E groups in four members of the family, and in the mother and the abnormal propositus, who had identical karyotypes, there was also a questionable abnormality of a B chromosome. Autoradiographic studies indicated that chromosomes 13 and 17 may be involved in the translocation and that the B-group abnormality involved possibly a chromosome No. 5. Genetic-marker studies were noncontributory. The explanation favored for the rearrangement was an insertion type of exchange following three breaks in the D and E groups, and hence the abnormal propositus could be explained as an example of recombinational imbalance.
Systematic problems in the amphibian family Lepto-dactylidae (Anura) as indicated by karyotypic analysis
Authors: Bogart J.P.
Published: April 2008

Somatic chromosomes obtained from corneal squash preparations of nine species representing four genera of the anuran family Leptodactylidae were analyzed and compared. Batrachyla leptopus, Crossodactylus gaudichaudii, Cyclorhamphus fuliginosus, Eupsophus coppingeri, E. taeniatus and Thoropa miliaris were found to possess 26 chromosomes (n = 13). E. roseus has 30 chromosomes (n = 15), E. vertebralis has 28 chromosomes (n = 14) and E. nodosus has 22 chromosomes (n = 11). The karyotypes of some species of Eupsophus are more similar intergenerically than intragenerically. This suggests that Eupsophus is an unnatural assemblage of species. Characters previously used to delimit genera of leptodactylid frogs are criticized.
Whole-mount electron microscopy of the centromere region of metacentric and telocentric mammalian chromosomes
Authors: Comings D.E. , Okada T.A.
Published: April 2008

Whole-mount electron microscopy of metaphase mouse L-cells showed that in many cases the region of the centromere was located at one extreme end of the chromosome with no evidence for short arms of any significant size. In such telocentric chromosomes there was only a single area of chromatid association. By contrast, the region of the centromere in mouse metacentric chromosomes was much longer. When well dispersed, it was seen to consist of two distinct areas of chromatid association, each of which was comparable in length to that of the telocentric chromosomes. In the region between these two areas there was a decrease in the density of the chromatin fibers. A similar quadripartite morphology was seen in human, Chinese hamster, and sheep metacentric chromosomes. These findings are most simply interpreted by the proposal that the quadripartite centromere of the metacentric chromosomes has resulted from the fusion of two telocentric chromosomes with bipartite centromeres.
A gross reduction in chiasma formation during meiotic prophase and a defective DNA repair mechanism associated with a case of human male infertility
Authors: Pearson P.L. , Ellis J.D. , Evans H.J.
Published: April 2008

Meiotic and histological studies have been carried out on testicular biopsies from an azoospermic human male who exhibited normal secondary sex characteristics. A failure in the formation of chiasmata during the first meiotic prophase resulted in a breakdown of the subsequent meiotic and spermatogenic processes. The few spermatozoa formed exhibited a range of DNA contents consistent with a random orientation and movement of the meiotic chromosomes. Radiation studies carried out on peripheral lymphocytes demonstrated that the patient had a reduced facility for chromosomal DNA repair. It is suggested that this defect gives an explanation for the failure of chiasma formation since chiasma formation probably involves a breakage, crossingover and repair of chromosomal DNA during the first meiotic prophase.
Deletions of the X chromosomes in Microtus agrestis cells in vitro
Authors: Cooper J.E.K. , Arrighi Francis E. , Hsu T.C.
Published: April 2008

A cell line from a female Microtus agrestis has been established in vitro, with most cells showing the normal female complement with two entire X chromosomes. Cloning of this line yielded stable cell strains, some of which showed deletions of the X chromosomes. Karyotypically, the deletions include (1) loss of the long arm of one X chromosome, (2) loss of one entire X chromosome, and (3) loss of one entire X chromosome together with loss of the long arm of the other X chromosome. In the last case, only the “functional” portion of the presumably active X chromosome remained. Radioautography has confirmed the actual loss of both constitutive and facultative heterochromatin from the X chromosomes in these clones. In addition, the parent cell line yielded a clone tolerant to 5-bromodeoxyuridine (BUdR) at 5 µg/ml. This cell strain retains thymidine kinase activity, however, as evidenced by uptake of thymidine, and by incorporation of BUdR into the DNA.
Apparent convergence of karyotypes in two species of pocket gophers of the genus Thomomys (Mammalia, Rodentia)
Authors: Berry D.L. , Baker R.J.
Published: April 2008

Intraspecific variation in chromosome morphology is greater in two species of pocket gophers than within any other presently studied mammalian species. Diploid number varies only from 76 to 78. Therefore, the majority of the differences appear to be the results of pericentric inversions. These geographical chromosomal differences in Thomomys bottae and T. umbrinus are best explained as adaptations to habitat characteristics. Within both species, populations occurring in arid or shallow soil habitats have karyotypes characterized by a high number of acrocentrics, whereas populations in more favorable conditions have karyotypes composed entirely of metacentrics or submetacentric elements. These parallel trends suggest that the symmetry of the karyotype as a whole may have functional significance.
The idiogram of the Venezuelan vole mouse, Akodon urichi venezuelensis Allen (Rodentia, Cricetidae)
Authors: Reig O.A. , Olivo Nelly , Kiblisky P.
Published: April 2008

The Venezuelan vole mouse, Akodon urichi venezuelensis, is a small South American cricetid which can be reared in the laboratory. Their somatic chromosomes have been morphologically and statistically investigated. The chromosome number is 2n = 18. The eight pairs of autosomes are metacentric; four pairs are similar in size and arm ratio, but the others are easy to identify. In males there is an XY sex-chromosome pair; the X is a submetacentric and duplicate type. Polymorphism has been found in the small-sized Y chromosome; in two out of six individuals it was an acrocentric and in the remaining four, a fully telocentric chromosome. In the females, the two X chromosomes are slightly heteromorphic; there is an X! quite similar to the male X chromosome and a longer X2, which differs also from the X1 in arm ratio. The risk of reversals of order in similar chromosomes is discussed.
Size classes of the head and flagellum of Drosophila spermatozoa
Authors: Beatty R.A. , Burgoyne P.S.
Published: April 2008

Among the different species and spermatozoan types of the genus Drosophila there is immense variation in the whole length of the spermatozoon (ca. 55 to 15,000 µ) and in the length of its head (ca. 7.5 to 60µ). The width of the head and tail is of the order of 0.5 µ. There are either one, two, or three principal size classes of spermatozoa in every male, the number being species-specific. More than one size class in individual animals will be referred to as polymegaly. Both the head and flagellum exhibit a closely related polymegaly. The correlation between head and flagellum length within a size class is zero. According to the species, Drosophila spermatozoa in the testis are known to occur in bundles of, for example, 128 spermatozoa, each bundle derived from a single spermatogonium. Polymegaly is found to exist between but not within bundles. Polymegaly cannot, therefore, be due to meiotic segregation of factors affecting spermatozoan size. An hypothesis that polymegaly arises by omission of one or more of the successive waves of mitotic division during formation of the bundle is apparently untenable. In species with polymegaly, spermatozoa of a length intermediate between those of the size classes typical of the species are virtually never released from the testis. All size classes of spermatozoa are motile and reach the female genital tract but seem not to be randomly disposed between the female storage organs. Much of the variation between size classes both within and between species of the genus seems to reflect an harmonious underlying pattern of a restricted number of size modules that follow a geometric progression. The modular size or sizes would be determined by the genome of the species, perhaps also by the sex-chromosome complement in particular and by the rearing temperature.
Length variation in the quinacrine-binding segment of human Y chromosomes of different sizes
Authors: Bobrow M. , Pearson P.L. , Pike M.C. , El-Alfi O.S.
Published: April 2008

The affinity of the long arm of the Ychromosome for quinacrine dihydrochloride has been used in a study of size variation in this chromosome. Measurements made on cells from 12 subjects with Y chromosomes of different sizes have clearly indicated that it is variation in the fluorescent area which accounts for the size differences. The nonfluorescent region of the chromosome is apparently stable. The possible significance of these findings is discussed.
Developmental anomaly in the mouse associated with triploidy
Authors: Wróblewska Joanna
Published: April 2008

Morphological studies of mouse embryos (F1hybrids between inbred strains of CBA females and CBA-T6T6 males) on the 9th, 10th, and 11th day of development revealed a characteristic disturbance in embryogenesis, inhibited development of the embryonic part of the egg-cylinder. This disturbance first appeared on the 9th day but did not affect the fetal membranes, which retained their normal appearance until the 11th day. All the egg-cylinders characterized by this anomaly were triploid. The presence of only one T6 marker chromosome showed that triploidy occurred as a result of digyny.
Chromosomal polymorphism in Peromyscus polionotus
Authors: Te G.A. , Dawson W.D.
Published: April 2008

Twenty-three oldfield mice, Peromyscus polionotus, representing six sources, were karyotyped. A structural polymorphism involving a moderately small pair of auto-somes was detected. This pair may be either acrocentric or bi-armed, resulting in karyograms showing 12, 12½, and 13 acrocentric pairs. The variation could be attributed to a single inversion widely distributed in the species. Minor structural variations in other autosomes also occurred. The karyotype of the F1 interspecific hybrid of P. maniculatus x P. polionotus was examined. The hybrid had an acro-centric:bi-armed chromosome ratio intermediate to the parent species.
Meiotic studies on a subfertile patient with a ring Y chromosome
Authors: Chandley Ann C. , Edmond P.
Published: April 2008

An account is given of a subfertile male carrying a ring Y chromosome in his blood. Meiotic investigations revealed that the X and ring Y chromosome remained unpaired at diakinesis, and maturation arrest between the first and second meiotic divisions was observed. The possible causes of the maturation arrest are discussed.
Sex-reversed mice: XX and XO males
Authors: Cattanach B.M. , Pollard C.E. , Hawkes S.G.
Published: April 2008

An autosomally inherited condition is described in the mouse which causes genetic females to develop as phenotypic males. XX males are phenotypically normal with the exception of small testes, which, in the adult, are devoid of germ cells. During late fetal and early postnatal development, male-type germ cells are present but progressively become lost, so that none is present by 10 days of age. XO males are also phenotypically normal, but spermatogenesis is active in the testis, and spermatozoa are produced. Cytological evidence of a Y-autosome translocation was completely lacking, and it is proposed that an autosomal dominant gene mutation, analogous to that found in other mammalian species, is responsible for the sex reversal.
Autosomal trisomy in lethal brachygnathia of cattle
Authors: Herzog A. , Höhn H.
Published: April 2008

Three further cases of the recently discovered “trisomy-brachygnathia syndrome” in cattle have been described. The syndrome consists of autosomal trisomy, brachygnathia inferior, and, in some cases, malformations such as arthrogryposis, hydrocephalus, cryptorchism, and heart anomalies. An indication of the possible genetical etiology of the syndrome is given by the teratograms of the sires.
Autoradiographic studies of cytogenetic effects induced by UV-inactivated measles virus (fusion factor) in human cells
Authors: Henry Sally , Cohen M.M. , Karzon D.T.
Published: April 2008

Two types of extensive chromosome changes (pulverization and uncoiling) as well as a combination of these phenomena in the same cell were induced by exposure to UV-inactivated measles virus (FF). The DNA-labeling patterns of these nuclear events were investigated. These types of extensive changes not only appeared to be morphologically distinguishable but also to be induced at different stages of the cell cycle. Pulverization occurred in very actively DNA-synthesizing cells. In contrast, G1, G2, or M cells were sensitive to uncoiling changes.
Isolation of aneusomic clones from Chinese hamster cell line following induction of nondisjunction
Authors: Kato H. , Yosida T.H.
Published: April 2008

A brief exposure of cells to Colcemid induces chromosomal nondisjunction. Making use of this behavior, we isolated several trisomic as well as monosomic cell clones from a cloned pseudodiploid Chinese hamster cell line. Karyotype analyses of these clones demonstrated that mainly small chromosomes such as Nos. 9 and 10 (or No. 11) were involved in chromosomal addition or loss. Nondisjunction was found to occur randomly in every member of the complement, but progeny cells possessing unbalanced chromosome constitutions, such as aneusomies of large chromosomes, appeared to die off or undergo karyotype remodeling by the time of the third or fourth mitosis after induction of nondisjunction.
Double monosomy mosaicism (45,X/45,XX,21–) in a retarded child with multiple congenital malformations
Authors: Weber Felice M. , Sparkes R.S. , Muller Helga
Published: April 2008

Double monosomy mosaicism was observed in a three-year-old girl who had mental and physical retardation. Routine blood-lymphocyte and bone-marrow chromosome studies showed an apparent 45, X pattern, which was confirmed by autoradiographic studies with tritiated thymidine. Routine and fluorescent chromosome analyses from bilateral skin biopsies revealed a 45,XX,21– karyotype, which was consistent with the positive sex-chromatin pattern in these fibroblasts as well as in the buccal smear and hair-root-sheath cells. Although her clinical features bore some resemblance to patients with Turner’s syndrome and to patients with G monosomy, our patient did not closely fit either of these syndromes.
Study of a patient with apparent monosomy 21 owing to translocation: 45,XX,21–,t(18q+)
Authors: Wyandt H.E. , Hecht F. , Lovrien E.W. , Stewart R.E.
Published: April 2008

A five-year-old girl with mild mental retardation and dyschondrosteosis was found to have 45 chromosomes. A G (21-22) chromosome was missing. The parents were chromosomally normal. Measurements confirmed the presence of an unusually long chromosome No. 17 or 18 in the girl’s karyotypes. Late labeling with 3H-thymidine and autoradiography showed it to be No. 18. By quinacrine fluoromicroscopy the apparently missing G chromosome proved to be No. 21. Thus, the apparent autosomal monosomy was the result of a de novo 18/21 translocation with loss of the short arm and centromere of No. 21 and of material from the long arms of No. 18 or No. 21 or both equivalent to two thirds of a G long arm. Although no evidence was found for deletion of a genetic marker, heterozygosity at five gene loci (MNSs, Jk, Hp, PGM, and AcP) excluded their deletion. We suggest that other instances of apparent autosomal monosomy may on careful study be found to be the result of similarly subtle chromosome rearrangements.
Autoradiographic study of DNA synthesis in homologous chromosomes distinguishable by morphology
Authors: de Capoa Adriana , Rocchi Angela , Miller Dorothy A. , Miller O.J.
Published: April 2008

Autoradiographic terminal labeling studies performed on leukocyte cultures of a man (A. de J.) and his son (H. de J.), both carriers of an enlarged satellite on a D-group chromosome, demonstrated that the morphological marker was a No. 15. Counts of grains on the long arms of the two chromosomes 15 showed that the marker chromosome was less heavily labeled than its normal homolog. This difference was highly significant in both cases. The marker chromosome was also shorter than its homolog, though not significantly so in one case. Possible interpretations of these findings, i.e., chromosomal polymorphism or autosomal lyonization, were discussed.
The in vitro stimulation of lymphocytes from peripheral blood and lymph nodes of the laboratory mouse
Authors: Bryan J.H.D. , Hybertson R.L.
Published: April 2008

The results of comparative studies of the efficacy of phytohemagglutinin (PHA-P) and pokeweed mitogen (PWM) as mitotic stimulators for in vitro cultures of mouse lymphocytes are reported. These studies have established that clearly defined optimal concentration ranges exist for each mitogen and that higher than optimal levels of either mitogen exert an inhibitory effect on cell proliferative activities. The levels of mitotic stimulation achieved with peripheral-blood cultures and with cultures of lymph-node lymphocytes should facilitate a variety of cytogenetic studies not heretofore practicable with the mouse.
Late labelling as an aid to chromosomal sexing of cultured mouse blood cells
Authors: McLaren Anne
Published: April 2008

A method is described for karyotypic sexing of cultured mouse blood cells, using both the morphological and the late-replicating properties of the Y chromosome. The misclassification rate is low, even when metaphase plates of poor quality are included.
Somatic pairing in Dipteran cells in culture
Authors: Nichols W.W. , Bradt Carole , Dwight Selena , Bowne W.
Published: April 2008

Somatic pairing of homologous chromosomes of Diptera insect cells is maintained in long-term tissue culture. In prophase and prometaphase the pairing extends throughout the length of the chromosomes and resembles meiotic pachytene. By metaphase the homologs are associated only in the pericentromeric areas, which persists through anaphase. The material is an excellent model for studies of this process and balanced somatic crossingover, which it permits.
Timing of DNA replication of autosomal heterochromatin in the hedgehog
Authors: Citoler P. , Gropp A. , Natarajan A.T.
Published: April 2008

The time sequence of DNA synthesis of autosomal constitutive heterochromatin and euchromatin was studied in kidney-cell cultures of the European hedgehog which had been pulse labeled with 3H-thymidine. The mean length of the S-period is 10.4 h for euchromatin and 5.2 h for constitutive heterochromatin. Thus the latter replicates DNA twice as fast as euchromatin. Constitutive heterochromatin starts replicating DNA about 7 h later and finishes 1.5 h later than euchromatin. The asynchrony of DNA synthesis between the two types of chromatin is particularly marked in the beginning of the S-phase. The inactive X chromosome also synthesizes DNA faster than euchromatin; it begins a short time before and finishes slightly after constitutive heterochromatin. The finding of accelerated DNA synthesis in autosomal heterochromatin lends itself to several possible explanations, although it remains difficult to understand fully at present.
Asynchronous centromere division in the Chinese hamster
Authors: Bregman A.A.
Published: April 2008

Asynchronous centromere division, i.e., variation in the distance between sister centromeres in the same cell, has been observed in bone-marrow cells of the Chinese hamster (2n = 22). The cells were harvested with brief hypotonic treatment but without colchicine. In each of 20 cells, the chromosomes were arranged in a sequence according to decreasing intercentromeric distance, i.e., the distance between sister centromeres. The 20 sequences exhibited a significant degree of concordance, permitting the construction of a best-estimate or overall sequence. There appears to be the same sequence among the chromosomes of each haploid set, although the two homologs of each pair ranked, on the average, 7.6 positions apart. The data on the X and Y chromosomes, which are morphologically distinguishable, indicate that the intercentromeric distance of the X is significantly larger than that of the Y. The concordance could be either an artifact of the harvest procedure (hypotonic treatment, flattening, etc.) or a result of the chromosomes dividing in a sequence at the onset of anaphase. These alternatives are discussed along with the relation of the findings to such chromosome characteristics as length and the time of DNA replication.
Comparison of banding patterns of human chromosomes obtained with heating, fluorescence, and proteolytic digestion
Authors: Dutrillaux B. , Finaz Catherine , De Grouchy J. , Lejeune J.
Published: April 2008

Banding patterns of human chromosomes obtained with various new techniques-quinacrine mustard staining, staining after heating, and staining after proteolytic digestion —are compared. Depending on the technique, the same band may be stained or not, but the sequence of the bands is identical with all techniques.
Pericentric inversions of chromosome 9 in two families
Authors: Wahrman J. , Atidia J. , Goitein R. , Cohen T.
Published: April 2008

Two similar pericentric inversions of chromosome 9 are transmitted in two unrelated families, each of which includes a consanguineous marriage. In both instances the inverted segment comprises the centromere region and the proximal part of the long arm, including the secondary constriction. The inverted chromosome was found in one homozygote and in three heterozygotes of the six karyotyped individuals of one family; in the second family, three of five karyotyped individuals were heterozygotes. The health problems of the propositi are apparently not associated with their chromosomal constitution.