Non-random position of homologous chromosomes (no. 9 and YY) in interphase nuclei of human fibroblasts (author's transl)]

The position of chromosomes No. 9 and of the Y chromosomes in interphase nuclei was observed by means of the Giemsa-11 staining and the quinacrine mustard fluorescence staining respectively. 3 fibroblast cultures from normal female persons and 1 culture from a person with the karyotype 47/XYY were used. The distance between the two homologous chromosomes was compared with the theoretical expected distance between two points which are randomly positioned in a circular area. The distance between the chromosomes No. 9 as well as between the two Y chromosomes is significantly smaller than expected with a random position. This tendency for a somatic association is stronger in the case of the two Y chromosomes than in the two chromosomes No. 9.     

Chromatin diminution and a chromosomal mechanism of sexual differentiation in Strongyloides papillosus

Eggs obtained from feces of rabbits infected with Strongyloides papillosus were squashed and the karyotypes were determined. They contained cells with either two long and two medium sized chromosomes (2L2M), or one long, three medium and one short chromosome (L3MS). Two types of parasitic female gonad could be distinguished on the basis of oocyte chromosome morphology at prometaphase of the maturation division. All the oocytes in a gonad contained either two upaired long chromosomes and two unpaired medium sized chromosomes, or two unpaired medium sized chromosomes and two unpaired chromosomes segmented into beads in one region. At the maturation division in mitotic parthenogenesis the beads appear to be lost from one of the chromosomes. This generates a medium sized and a shorter chromosome, which together with the undiminished chromosomes make up the L3MS karyotype. Animals with beaded oocyte chromosomes lay eggs that develop into males. It is suggested that males are heteromorphic for the long homologue due to chromatin diminution, that occurs in the maturation division of mitotic parthenogenesis.     

Distributive Disjunction of Authentic Chromosomes in Saccharomyces Cerevisiae

Distributive disjunction is defined as the first division meiotic segregation of either nonhomologous chromosomes that lack homologs or homologous chromosomes that have not recombined. To determine if chromosomes from the yeast Saccharomyces cerevisiae were capable of distributive disjunction, we constructed a strain that was monosomic for both chromosome I and chromosome III and analyzed the meiotic segregation of the two monosomic chromosomes. In addition, we bisected chromosome I into two functional chromosome fragments, constructed strains that were monosomic for both chromosome fragments and examined meiotic segregation of the chromosome fragments in the monosomic strains. The two nonhomologous chromosomes or chromosome fragments appeared to segregate from each other in approximately 90% of the asci analyzed, indicating that yeast chromosomes were capable of distributive disjunction. We also examined the ability of a small nonhomologous centromere containing plasmid to participate in distributive disjunction with the two nonhomologous monosomic chromosomes. The plasmid appeared to efficiently participate with the two full length chromosomes suggesting that distributive disjunction in yeast is not dependent on chromosome size. Thus, distributive disjunction in S. cerevisiae appears to be different from Drosophila melanogaster where a different sized chromosome is excluded from distributive disjunction when two similar size nonhomologous chromosomes are present.     

CYTOLOGICAL STUDIES OF OEDOGONIUM. II. CHROMOSOME NUMBERS IN TWELVE SPECIES OF OEDOGONIUM

Mitotic chromosome counts are reported for 12 species of Oedogonium with the following distribution: two species with 13 chromosomes, two species with 16 chromosomes, five species with 17 chromosomes one species with 19 chromosomes, one species with 32 chromosomes, and one species with 38 + 1 chromosomes. Diploid strains of two species are illustrated and discussed. Cytological comparison of species establishes that there is great diversity in Oedogonium with relation to chromosome number, size, and morphology.     

Origin of B chromosomes in cultivated rye.

Cultivated rye (Secale cereale) and its weedy relative (S. segetale) carry B chromosomes. The B chromosomes are known to be morphologically alike at somatic metaphase and they are of the standard type in natural populations. To clarify the cytogenetic relationship between the standard B chromosomes of S. cereale and those of S. segetale, we made four crosses between Afghan S. segetale with two standard B chromosomes as a pistillate parent and Turkish, Iranian, Korean, and Japanese S. cereale, all with two standard B chromosomes as pollen parents. We observed the pairing of B chromosomes at diakinesis in pollen mother cells in all F1 hybrids with four standard B chromosomes, two from each of the pistillate and the pollen parents. The degree of pairing of B chromosomes in all F1 hybrids with four standard B chromosomes was similar to or somewhat lower than, that in parental strains with four standard B chromosomes. These results showed that the standard B chromosomes in S. segetale from Afghanistan are homologous with those in S. cereale from Turkey, Iran, Korea, and Japan. We therefore propose monophyletic origin of the standard B chromosomes in S. segetale and S. cereale.     

Meiotic Disjunction of Homologs in Saccharomyces Cerevisiae Is Directed by Pairing and Recombination of the Chromosome Arms but Not by Pairing of the Centromeres

We explored the behavior of meiotic chromosomes in Saccharomyces cerevisiae by examining the effects of chromosomal rearrangements on the pattern of disjunction and recombination of chromosome III during meiosis. The segregation of deletion chromosomes lacking part or all (telocentric) of one arm was analyzed in the presence of one or two copies of a normal chromosome III. In strains containing one normal and any one deletion chromosome, the two chromosomes disjoined in most meioses. In strains with one normal chromosome and both a left and right arm telocentric chromosome, the two telocentrics preferentially disjoined from the normal chromosome. Homology on one arm was sufficient to direct chromosome disjunction, and two chromosomes could be directed to disjoin from a third. In strains containing one deletion chromosome and two normal chromosomes, the two normal chromosomes preferentially disjoined, but in 4-7% of the tetrads the normal chromosomes cosegregated, disjoining from the deletion chromosome. Recombination between the two normal chromosomes or between the deletion chromosome and a normal chromosome increased the probability that these chromosomes would disjoin, although cosegregation of recombinants was observed. Finally, we observed that a derivative of chromosome III in which the centromeric region was deleted and CEN5 was integrated at another site on the chromosome disjoined from a normal chromosome III with fidelity. These studies demonstrate that it is not pairing of the centromeres, but pairing and recombination along the arms of the homologs, that directs meiotic chromosome segregation.     

Comportement des chromosomes surnuméraires et relation avec le taux de mortalité dans une population africaine de Locusta migratoria migratorioides

Transmission of supernumerary chromosomes is studied in adults and embryos of an African population of Locusta migratoria migratorioides; 34% of the animals show one or two B chromosomes (24% one, 10% two). This percentage is the same in both sexes. During mitosis, B chromosomes are very stable. At meiosis, in some cases they show pairing, in other cases they enter as univalents. The eventuality of synapsis or association is discussed. These two kinds of behaviour could not be explained by the presence of two different B chromosomes as is shown from the study of parthenogenetic progeny. Repartition of B chromosomes in the progeny is different depending on whether the male or the female parent supplies them; so the behaviour of these supernumerary should be conditioned, not by their own structure, but by a connection with the cell. — One B chromosome apparently is neutral. When there are two B chromosomes, in case of synapsis, the number of animals with two B in the progeny is slightly lower than previous; in case of asynapsis, there is a higher lethality of individuals and oocytes with two B chromosomes.     

RanGTP and the actin cytoskeleton keep paternal and maternal chromosomes apart during fertilization

Zygotes require two accurate sets of parental chromosomes, one each from the mother and the father, to undergo normal embryogenesis. However, upon egg–sperm fusion in vertebrates, the zygote has three sets of chromosomes, one from the sperm and two from the egg. The zygote therefore eliminates one set of maternal chromosomes (but not the paternal chromosomes) into the polar body through meiosis, but how the paternal chromosomes are protected from maternal meiosis has been unclear. Here we report that RanGTP and F-actin dynamics prevent egg–sperm fusion in proximity to maternal chromosomes. RanGTP prevents the localization of Juno and CD9, egg membrane proteins that mediate sperm fusion, at the cell surface in proximity to maternal chromosomes. Following egg–sperm fusion, F-actin keeps paternal chromosomes away from maternal chromosomes. Disruption of these mechanisms causes the elimination of paternal chromosomes during maternal meiosis. This study reveals a novel critical mechanism that prevents aneuploidy in zygotes.     

Studies on rodent chromosomes

The karyotype ofTatera indica cuverii consists of 68 chromosomes with two X chromosomes in the female and an X and a Y chromosome in the male. The X chromosomes are the largest and can be distinguished from each other morphologically. Autoradiographic studies indicate that the two morphologically distinguishable X chromosomes are out-of-phase in DNA replication in approximately equal proportion and thus substantiate the random inactivation hypothesis.     

High resolution chromosome analysis: one and two parameter flow cytometry

Isolated mammalian chromosomes have been quantitatively classified by high resolution flow cytometry. Chinese hamster chromosomes stained with 33258 Hoechst and excited in the UV showed a fluorescence distribution in which the 14 types of Chinese hamster chromosomes were resolved into 16 groups seen as distinct peaks in the distributions. Chinese hamster chromosomes were also stained with both 33258 Hoechst (HO) and chromomycin A3 (CA3); the two dye contents were measured by selective excitation in the UV and at 458 nm in a dual beam flow cytometer. The resulting two parameter distribution (HO versus CA3) showed 10 chromosome groups¹. Human strain LLL 761 chromosomes stained with HO and excited in the UV showed a fluorescence distribution in which the 23 types of human chromosomes were resolved into 12 groups. Human chromosomes stained with both HO and CA3 and measured in the dual beam flow cytometer produced two parameter fluorescence distributions which showed 20 groups. The chromosomes associated with each group were determined by quinacrine banding analysis of sorted chromosomes and by DNA cytophotometry of preidentified metaphase chromosomes. The relative HO and CA3 stain content and frequency of occurrence of chromosomes in each group were determined from the fluorescence distributions and compared to the results from DNA cytophotometry. The chromosome to chromosome variations in HO and CA3 staining are attributed to variations in chromosomal base composition.     

萝卜蚜和豆蚜染色体C-带带型比较与分析

本研究利用C-带技术,显示出萝卜蚜和豆蚜的染色体C-带带型,并进行了初步分析。萝卜蚜与豆蚜的染色体在组型上只有第4对染色体稍有区别;在带型上两者有很明显的差异。萝卜蚜有2对散漫着丝粒染色体,豆蚜没有该种染色体。豆蚜的第4对染色体在端部缺少-C带带纹。萝卜蚜的第2对染色体与豆蚜的第2对染色体带型相似。根据萝卜蚜和豆蚜的C-带带型,讨论了二者在进化中的亲缘关系。     

Comparative karyotype analysis ofCeratozamia mexicana andMicrocycas calocoma (Zamiaceae) using fluorochrome banding (CMA/DAPI) and fluorescence in situ hybridization of ribosomal DNA

Orcein staining, differential staining with CMA and DAPI, and FISH with an rDNA probe were used to compare somatic chromosomes ofCeratozamia mexicana andMicrocycas calocoma. CMA-positive dots and hybridization signals appeared on chromosomes at early interphase and mitotic prophase, but in significantly different number in the two species. InCeratozamia mexicana, the CMA-positive and DAPI-negative bands and the hybridization signal were located at the terminal region of the long arm of three median-centromeric chromosomes, the terminal region of the short arm of two median-centromeric chromosomes and the terminal region of the long arm of two subterminal-centromeric chromosomes. InMicrocycas calocoma, they were located at the pericentric region of two median-centromeric chromosomes. These chromosome data suggested thatMicrocycas has no simple Robertsonian relationship toCeratozamia.     

C-banded karyotypes of two Silene species with heteromorphic sex chromosomes.

Mitotic metaphase chromosomes of Silene latifolia (white campion) and Silene dioica (red campion) were studied and no substantial differences between the conventional karyotypes of these two species were detected. The classification of chromosomes into three distinct groups proposed for S. latifolia by Ciupercescu and colleagues was considered and discussed. Additionally, a new small satellite on the shorter arm of homobrachial chromosome 5 was found. Giemsa C-banded chromosomes of the two analysed species show many fixed and polymorphic heterochromatic bands, mainly distally and centromerically located. Our C-banding studies provided an opportunity to better characterize the sex chromosomes and some autosome types, and to detect differences between the two Silene karyotypes. It was shown that S. latifolia possesses a larger amount of polymorphic heterochromatin, especially of the centromeric type. The two Silene sex chromosomes are easily distinguishable not only by length or DNA amount differences but also by their Giemsa C-banding patterns. All Y chromosomes invariably show only one distally located band, and no other fixed or polymorphic bands on this chromosome were observed in either species. The X chromosomes possess two terminally located fixed bands, and some S. latifolia X chromosomes also have an extra-centric segment of variable length. The heterochromatin amount and distribution revealed by our Giemsa C-banding studies provide a clue to the problem of sex chromosome and karyotype evolution in these two closely related dioecious Silene species.     

Microdissection and PCR Amplification of Single Soybean Chromosome

Glass needles were successfully used to dissect the soybean (Glycine max L. ) single chromosome under the micromanipulator in this research. Two dissected soybean chromosomes were digested by Sau3A in two 0.5 mL Eppendorf tubes respectively. The two ends of chromosomal fragments were ligated with Sau3A linker adoptor. After two rounds of PCR amplification, smear DNA fragments ranged from 0.3 to 3 kb were acquired. Southern hybridization result showed the PCR products from the two single soybean chromosomes were homogeneous with the soybean genomic DNA, indicating that DNAs from the two single chromosomes have been successfully amplified. At the same time, the amplified products from the two of the distinguished single chromosome appeared somewhat different. The authors dissected the small chromosomes only by a traditional inverted microscope. Therefore, this research provides a plausible chance for amplification and microcloning of single small chromosomes.     

A brief history of human autosomes.

Comparative gene mapping and chromosome painting permit the tentative reconstruction of ancestral karyotypes. The modern human karyotype is proposed to differ from that of the most recent common ancestor of catarrhine primates by two major rearrangements. The first was the fission of an ancestral chromosome to produce the homologues of human chromosomes 14 and 15. This fission occurred before the divergence of gibbons from humans and other apes. The second was the fusion of two ancestral chromosomes to form human chromosome 2. This fusion occurred after the divergence of humans and chimpanzees. Moving further back in time, homologues of human chromosomes 3 and 21 were formed by the fission of an ancestral linkage group that combined loci of both human chromosomes, whereas homologues of human chromosomes 12 and 22 were formed by a reciprocal translocation between two ancestral chromosomes. Both events occurred at some time after our most recent common ancestor with lemurs. Less direct evidence suggests that the short and long arms of human chromosomes 8, 16 and 19 were unlinked in this ancestor. Finally, the most recent common ancestor of primates and artiodactyls is proposed to have possessed a chromosome that combined loci from human chromosomes 4 and 8p, a chromosome that combined loci from human chromosomes 16q and 19q, and a chromosome that combined loci from human chromosomes 2p and 20.     

Evolutionary implications of permanent odd polyploidy in the stable sexual, pentaploid of Rosa canina L

In Rosa canina (2n = 5x = 35), the pollen and ovular parents contribute, respectively, seven and 28 chromosomes to the zygote. At meiosis I, 14 chromosomes form seven bivalents and 21 chromosomes remain as univalents. Fluorescent in situ hybridization to mitotic and pollen mother cells (PMC) of R. canina showed that 10 chromosomes (two per genome) carry ribosomal DNA (rDNA) loci. Five chromosomes carry terminal 18S-5.8S-26S rDNA loci; three of these also carry paracentric 5S rDNA loci and were designated as marker chromosomes 1. Five chromosomes carry only 5S rDNA loci and three of these were designated as marker chromosomes 2. The remaining four of the 10 chromosomes with rDNA loci were individually identifiable by the type and relative sizes of their rDNA loci and were numbered separately. At PMC meiosis, two marker chromosomes 1 and two marker chromosomes 2 formed bivalents, whereas the others were unpaired. In a gynogenetic haploid of R. canina (n = 4x = 28), obtained after pollination with gamma-irradiated pollen, chromosomes at meiosis I in PMC remained predominantly unpaired. The data indicate only one pair of truly homologous genomes in R. canina. The 21 unpaired chromosomes probably remain as univalents through multiple generations and do not recombine. The long-term evolutionary consequence for the univalents is likely to be genetic degradation through accumulated mutational change as in the mammalian Y chromosome and chromosomes of asexual species. But there is no indication that univalents carry degenerate 5S rDNA families. This may point to a recent evolution of the R. canina meiotic system.     

Chromosome evolution in fish: BrdU replication patterns demonstrate chromosome homeologies in two species of the genus Astyanax

A comparison of R-banding patterns obtained by 5-bromodeoxyuridine incorporation was made between the chromosomes of two fish species of the genus Astyanax (Characiformes: Tetragonopterinae), A. altiparanae with 2n = 50 chromosomes, and A. schubarti with 2n = 36 chromosomes. The two species present the highest and the lowest chromosome numbers found in this fish genus, respectively, for which the modal chromosome number is 50. R-band homeology was detected, involving eleven chromosomes of A. schubarti and seventeen chromosomes of A. altiparanae, indicating a close chromosomal relationship between the two species, in spite of their great difference in chromosome number. A chromosome fusion in the past history of the group was hypothesized as a possible cause of the discrepant chromosome numbers of the two species.     

Mapping of rDNA on the chromosomes of Eleusine species by fluorescence in situ hybridization

Mapping of rDNA sites on the chromosomes of four diploid and two tetraploid species of Eleusine has provided valuable information on genome relationship between the species. Presence of 18S-5.8S-26S rDNA on the largest pair of the chromosomes, location of 5S rDNA at four sites on two pairs of chromosomes and presence of 18S-5.8S-26S and 5S rDNA at same location on one pair of chromosomes have clearly differentiated E. multiflora from rest of the species of Eleusine. The two tetraploid species, E. coracana and E. africana have the same number of 18S-5.8S-26S and 5S rDNA sites and located at similar position on the chromosomes. Diploid species, E. indica, E. floccifolia and E. tristachya have the same 18S-5.8S-26S sites and location on the chromosomes which also resembled with the two pairs of 18S-5.8S-26S rDNA locations in tetraploid species, E. coracana and E. africana. The 5S rDNA sites on chromosomes of E. indica and E. floccifolia were also comparable to the 5S rDNA sites of E. africana and E. coracana. The similarity of the rDNA sites and their location on chromosomes in the three diploid and two polyploid species also supports the view that genome donors to tetraploid species may be from these diploid species.     

Heterochromatin and chromosomal aberration in microtus agrestis: role of chromosomal association

Mitomycin C (MC) -induced chromatid aberrations among the chromosomes of Microtus agrestis are preferentially localized in the constitutive heterochromatic regions, i.e., major part of the sex chromosomes and the centromeric regions of the autosomes. In the sex chromosomes, intrachanges predominate, while interchanges between the two X chromosomes are very rare. This pattern of distribution of different types of aberrations is interpreted as due to the individual chromocentres that are formed by the two X chromosomes in the interphase.     

Variation of wheatgrass chromosomes in wheat-wheatgrass alien addition line "TAI-27"revealed by fluorescence in situ hybridization (FISH)

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