A Cytological Basis for a Map of the Nucleolar Chromosome in Man*

Schultz, Jack C.; Lawrence, Patricia

doi:10.1093/oxfordjournals.jhered.a105979

Cited by 55 publications

(7 citation statements)

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“…However, where the male is heterogametic and all the products of meiosis are functional, non-randomness could have no role without the further assumptions that there is, in fact, an orientation of the second meiotic division spindle with respect to ihe first and that some physiological or genetic mechanism (as, for instance, chi-omatid bridges involving any one of the autosomes) operates to eliminate certain of the spermatids differentially. Evidence available at present does not support such a scheme (SCHULTZ and ST. LAWRENCE 1949) but without a more thorough knowledge of the chromosome behaviour in such cases it cannot be dismissed as a possibility to account for some measure of the observed discrepancies in the primary sex ratio.…”

Section: Methodsmentioning

confidence: 99%

NONRANDOM DISJUNCTION IN DROSOPHILA

Novitski¹

1967

Annu. Rev. Genet.

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HE stability of the ring chromosomes in Drosophila melanogaster raises T certain questions about the nature of chromosome structure and reduplication, since it seems possible that such chromosomes would be subject to loss by interlocking of daughter chromatids after reduplication. In a set of experiments designed to determine the extent to which newly derived ring chromosomes might be lost at the meiotic divisions, it has been found that the generalization that disjunction of chromatids at the second meiotic division is random does not appear to be completely valid when the chromatids are structurally different. The evidence for such non-randomness is presented below. EXPERIMENTS INVOLVING ATTACHED X CHROMOSOMESThe type of genetic constitution which regularly manufactures ring chromosomes is that used by SIDOROV, SOKOLOV and TROFIMOV (1935, 1936) and by STURTEVANT and BEADLE (1936) in their demonstration of single crossing over within heterozygous inversions. The essential features of their analyses of the results of crossing over in this type of tetrad are incorporated into figure 1. At the reduction division the X-chromatids separate from the Ychromatids ; the figure shows only the second division segregation for the X-chromatids. The tetrads with no, one, or two exchanges are represented by the symbols EO, E1 or EQ, respectively. The two exchange tetrads (Ez) may involve 2, 3, or 4 strands and are designated as Ez-2s, EQ-3s and E2-4s. It is to be noted that there are two different genetic consequences from the single exchange tetrads (El), and two from each of the three types of two exchange tetrads (Ez-Zs, Ez-3.S and E2-4~). These different possibilities are distinguished by the letters a and b following the tetrad type. Three exchange tetrads are not considered here since, as will be shown below, they are relatively rare and can contribute little to the analysis.From figure 1 it is clear that 50 percent is the maximum frequency with which rings may be expected, regardless of the distribution of tetrads of the different ranks since the no-exchange tetrads give rise only to attached X's and the two-exchange tetrads to 50 percent more attached, X's than rings in the viable X-chromosome-bearing gametes.Neither the work of SIDOROV, SOKOLOV and TROFIMOV nor that of STURTE-VANT and BEADLE suggests any deficiency of the ring class. In the first case,

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Section: Methodsmentioning

confidence: 99%

NONRANDOM DISJUNCTION IN DROSOPHILA

Novitski¹

1967

Annu. Rev. Genet.

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“…1 and/or No. 9) have been questioned as to their role in nucleoli organization (16,44). At late telophase stages in the Chinese hamster and human cells, at least eight to ten sites for nucleoli organization are inferred from the maximum number of nucleoli seen at this stage.…”

Section: Sites Of Nueleolar Persistence Related To Sites Of Nucleolarmentioning

confidence: 99%

Persistence of Nucleoli in Short Term and Long Term Cell Cultures and in Direct Bone Marrow Preparations in Mammalian Materials

Heneen¹,

Nichols²

1966

The Journal of Cell Biology

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Persistent nucleoli were studied in Chinese hamster and human long term cultures, human peripheral blood short term cultures, as well as direct bone marrow preparations. No colchicine or hypotonic treatments were applied and the cells were differentially stained with the Feulgen method and light green. Nucleoli were found to persist in the three systems studied, although to a much greater extent in the long term culture. The persistent nucleolar materials were usually in the form of individualized nucleoli mainly at chromosome ends. They also sometimes existed in a fluidlike or dropletlike condition around the chromosomes. Association of acrocentrics in humans and end-to-end associations in hamsters are likely to result from persistence of nucleoli and the possible effects of colchicine and hypotonic treatments that are usually applied. Other phenomena, such as stickiness at metaphase and separation difficulties and fragmentation at anaphase, may result from persistence of nucleoli. Nucleoli were often associated with large chromosomes and sometimes at sites exhibiting faint or clear constrictions. The possibilities of a partial correspondence between sites of persistence and sites of organization, as well as of the organization of nucleolar materials at sites other than the main organizers, are discussed. The persistent nucleoli were not included in daughter nuclei. They either degenerated in the cytoplasm or were eliminated from the cell. The three systems used may represent different intensities of metabolism reflected in the amounts of nucleolar materials built up and the amount that persists.

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“…More recently there has again been some confusion about the human nucleolus by Schultz and St Lawrence (1949), who described what they call the 'nucleolar chromosome' of man at pachytene. They have attempted to make a pachytene map of this 'nucleolar chromosome' but experienced some ditliculty in that the 'nucleolus ' appeared to be sometimes attached to the middle, sometimes to the end, and sometimes near the end of a pachytene pair of chromosomes.…”

Section: The Formation Of a Sex Vesicle At Meiosismentioning

confidence: 99%

Sex-Linkage and the Sex Chromosomes in Man

Sachs

1952

Annals of Eugenics

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A Cytological Basis for a Map of the Nucleolar Chromosome in Man*

Cited by 55 publications

References 0 publications

NONRANDOM DISJUNCTION IN DROSOPHILA

NONRANDOM DISJUNCTION IN DROSOPHILA

Persistence of Nucleoli in Short Term and Long Term Cell Cultures and in Direct Bone Marrow Preparations in Mammalian Materials

Sex-Linkage and the Sex Chromosomes in Man

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