Changes in the fluorescence patterns of translocated Y chromosome segments in Drosophila melanogaster

Fluorescence analysis after quinacrine staining in squashes of Varese wild stock male larval ganglia confirmed that the Y chromosome has four characteristic sections of bright fluorescence. In one Y/X and in one Y/III translocation the section of bright fluorescence on the short arm of the Y is no longer bright when translocated onto the terminal portion of the X and on the right arm of the III chromosome, respectively. Fluorescence analysis has also permitted the identification of a structurally abnormal Y chromosome in a cell line of Drosophila melanogaster established in vitro. The findings in the two translocations call for caution in the interpretation of structural rearrangements by fluorescence analysis.     

Synaptonemal complex of the sex-autosome trivalent in a male Indian muntjac

Bright-field microscopy of silver-stained pachytene spermatocytes of a male Indian muntjac, Muntiacus muntjak revealed that (a) the synapsis between the autosomal homologs, including the long arm of the X and Y₂, was normal, (b) the nucleolus organizer regions were present in both the No. 1 bivalent and the long arm of the X and Y₂, (c) the accessory structures of the X chromosome short arm in the forms of light and dark thickenings and the hairpin-like bend were present despite the X-autosome translocation, (d) a short synaptonemal complex was present between the Y₁ (real Y) and the short arm of the X chromosome, and (e) the centromeric orientation of the Y₁ and Y₂ chromosomes was in Cis configuration as opposed to the X chromosome.     

Characterization of a new aberration of the human Y chromosome by banding methods and DNA restriction endonuclease analysis

Summary Comparative cytogenetic analyses were performed with ten different banding methods on a previously undescribed, inherited structural aberration of a Y chromosome, and the results compared with those of normal Y chromosomes occurring in the same family. The value of the individual staining techniques in investigations of Y chromosomal aberrations is emphasized. The aberrant Y chromosome analyzed can be formally derived from an isodicentric Y chromosome for the short arm with a very terminal long-arm breakpoint, in which the centromere, an entire short arm, and the proximal region on one long arm was lost. This interpretation was confirmed by determining the amount of the two Y-specific DNA sequences (2.1 and 3.4 kb in length) by means of HaeIII restriction endonuclease analysis. The karyotype-phenotype correlations in the men with this aberrant Y chromosome, especially the fertility dysfunctions (oligoasthenoteratozoospermia, cryptozoospermia), are discussed. The possibility of the existence of fertility factors involved in the control of spermatogenesis within the quinacrine-bright heterochromatic region of the Y long arm is presented.     

Heterochromatin, synaptonemal complex, and NOR activity in the somatic and germ cells of a male domestic dog, Canis familiaris (Mammalia, Canidae)

C-banding and silver staining of the somatic and germ cells of the male domestic dog. Canis familiaris, have shown that: (1) the amount of C-banding is small compared to most other mammalian species, (2) three pairs of autosomes have nucleolus organizer regions (NORs) at the terminal ends of their long arms, whereas the Y chromosome has an NOR on the terminal end of the short arm, (3) the organization of the synaptonemal complex (SC) is similar to that of other mammalian species, (4) a distinct SC is formed between the long arm of the Y chromosome and probably the short arm of the X chromosome, and (5) the differential axes of both sex chromosomes do not demonstrate fusiform thickenings nor do they stain darkly with silver as do the XY bivalents in many other mammalian species.     

Cytological localization of ribosomal cistrons in polytene chromosomes of Phaseolus coccineus

Tritiated ribosomal RNA (rRNA) was prepared from hypocotyls of Phaseolus coccineus grown in liquid culture in the dark and in presence of 5-³H-uridine. A mixture of the 18S and 25S ³H-rRNA fractions was used for hybridization with DNA in the polytene chromosome cells of the embryo suspensor of P. coccineus. It was shown that the ribosomal cistrons (rDNA) are located in the nucleolus organizing system (satellite, nucleolar constriction and organizer) of the satellited chromosome pairs I (S₁) and V (S₂), in the proximal heterochromatic segment of the long arm of chromosomes S₁ and in the terminal heterochromatic segment of chromosome pair II. The micronucleoli which are produced by the satellite and nucleolus organizer of the chromosome pair S₁ contain rDNA; on the contrary, no rRNA-DNA hybridization is found in the DNA containing granules which are produced by the satellite and nucleolus organizer of chromosome pair S₂. The DNA which is amplified during production of DNA puffs at some chromosomal regions apparently does not code for ribosomal RNA (no detectable rRNA-DNA hybridization).Publication no. 62 from the Laboratorio di Mutagenesi e Differenziamento, Consiglio Nazionale delle Ricerche, Pisa. Part of the investigation was supported by Contract SC 001/076-69-1 BIAN between the European Atomic Energy Community and the University of Pisa, Institute of Genetics.     

Cytological localization of the genes for the four classes of ribosomal RNA (25S, 18S, 5.8S and 5S) in polytene chromosomes of Phaseolus coccineus

Homologous tritiated 25S, 18S and 5.8S rRNAs were used separately for in situ hybridization to the polytene chromosomes of the embryo suspensor cells of Phaseolus coccineus. Hybridization occurred at the same chromosomal sites which were labeled in previous in situ hybridization experiments with 25+18S rRNAs in the same material (Avanzi et al., 1972), namely: nucleolus organizing system (satellite, nucleolar constriction and organizer) of chromosome pairs I (S₁) and V (S₂), proximal heterochromatic segment of the long arm of chromosome pair I, and terminal heterochromatic segment of chromosome pair II. Competition hybridization experiments confirmed for P. coccineus the high sequence homology between 25S and 18S rRNA already known for other plants.Homologous ¹²⁵I-5S rRNA was found to hybridize to three sites in the polytene chromosomes of P. cocdneus: the proximal heterochromatic segment in the long arm of chromosome pair I (which also bears the sequences complementary to 25S, 18S and 5.8S RNAs), most of the proximal heterochromatic segment plus a small portion of adjoining euchromatin in the long arm of chromosome pair VI and the large intercalary heterochromatic segment in the same chromosome pair. Simultaneous labeling of the two 5S RNA sites in chromosome VI was quite rare (3%), the rule being labelling of one site to the exclusion of the other, with a labeling frequency of 43.7% and 53.3% for sites no. 1 and no. 2 respectively. These results are interpreted as being due to differential hybridizability of chromosomal sites such as described in other materials.     

Morphology of the pachytene chromosomes ofPennisetum purpureum schumach

The morphology of the pachytene chromosomes ofPennisetum purpureum was studied. On the basis of relative lengths and arm ratios it was possible to identify them individually. They are numbered 1 to 14 in the order of their decreasing lengths and diagnostic characters are given for each chromosome. The first and the fourteenth chromosomes, the longest and the shortest of the complement respectively, are the nucleolus organizing chromosome. In all the fourteen chromosomes the centromeres are flanked by deep staining regions. This feature is common to the two species.P. typhoides andP. purpureum. Seven out of the fourteen chromosomes have terminal knobs in their long arms. This is a feature in which it differs from the other seven chromosome species.Pennisetum typhoides. These knobs, however, are not present uniformly in all populations; material obtained from Ghana did not show these knobs.     

Speciation and chromosomal evolution of the Baikalian endemic chironomids of the genus Sergentia Kief. (Diptera, Chironomidae): Karyotype divergence and chromosomal polymorphism in the populations of deep-water species Sergentia nebulosa Linevitsh et al. and Sergentia assimilis Proviz V. et Proviz L.

Specific karyotype structure and chromosomal polymorphism was investigated in the populations of Sergentia nebulosa Linevitsh et al., 1984 and Sergentia assimilis Proviz V. et Proviz L., 1999, the deep-water endemic chironomid species (Diptera, Chironomidae) from the Baikal Lake. The distinguishing feature of the karyotypes of these species, compared to the other Baikalian Sergentia, is well-developed nucleolus in region 6 of arm C. Both species display the presence of interspecific population polymorphism, determined by the structure of this arm. In some populations, chromosome regions from 4 to 6 contain a homozygous inversion, which is absent in the other populations. The distinguishing karyotype feature of S. assimilis, which shares fluctuating homozygous inversions with the other species, is the presence of two species-specific homozygous inversions. These are the secondary overlapping inversion in arm A, regions 2 to 7, and the inversion in regions 4 to 10 of arm G. Both species of interest contain nucleolus organizer in region 10 of arm G. In populations of S. nebulosa, six heterozygous inversions localized in arms A, B, C, F, and G were discovered. The highest number of heterozygotes for inversions (71%) was observed in the population from Southern Baikal. In arm B of S. assimilis, one heterozygous inversion and heterozygosity for nucleolus organizer in the chromosome region 16 was detected. Chromosomal evolution of Baikalian Sergentia, and the role of inversion polymorphism in the population adaptation is discussed. Original Russian Text ? V.I. Proviz, 2008, published in Genetika, 2008, Vol. 44, No. 12, pp. 1627–1637.     

A de novo satellited short arm of the Y chromosome possibly resulting from an unstable translocation

A satellited long arm of the Y chromosome (Yqs) is considered a normal variation, whereas the presence of a satellite on the short arm of the Y (Yps) has never been described in the literature. A Yps chromosome could be clinically significant if the translocation resulting in Yps has relocated the testis-determining gene, SRY, to another chromosome. A carrier of such a translocation would therefore be at increased risk for having XX male and XY female offspring. Here we describe the first reported case of de novo Yps present in a phenotypically normal male. This Yps chromosome was positive for C-banding and nucleolus organizer region (NOR) staining and showed a hybridization signal for the -satellite sequence. Fluorescence in situ hybridization (FISH) analysis indicated that SRY was retained on the Yps and the translocation breakpoint on Yps was distal to the pseudoautosomal region. At prenatal diagnosis, a normal appearing Y chromosome was found in his son, and thus the satellite on Yps was lost during meiotic Xp-Yp pairing. This Yps chromosome was likely the product of an unstable translocation.     

Chromosomes and DNA of Mus

Using C-banded preparations of Mus dunni it is possible to study the behavior of constitutive heterochromatin in early stages of meiotic prophase. The X and the Y chromosomes, both of which contain a large amount of heterochromatin, lie apart in leptotene but move toward each other during zygotene. They then form the sex vesicle at late zygotene. In autosomes zygotene pairing appears to start from the telomeric ends. The centromere of the Y chromosome associates end-to-end with the terminal end of the long arm of the X chromosome. The autosomal heterochromatic short arms show forked morphology in certain bivalents at pachytene, suggesting probable incomplete synapsis.     

Origin and Differentiation of a Sex Chromosome System in Parodon hilarii (Pisces, Parodontidae). Satellite DNA, G- and C-banding

A satellite DNA sequence of Parodon hilarii (named pPh2004) was isolated, cloned and sequenced. This satellite DNA is composed of 200 bp, 60% AT rich. In situ hybridization (FISH) results revealed that the satellite DNA pPh2004 is located in the terminal regions of several chromosomes, forming highly evident blocks in some and punctual marks in others. The comparison between the FISH and C-banding results showed that the location of this satellite DNA coincides with that of most terminal heterochromatins. However, some regions are only marked by FISH whereas other regions are only marked by C-banding. The possible existence of more than one satellite DNA family could explain these partial differences. The in situ hybridization with the satellite DNA and the G- and C-bandings confirmed the presence of a sex chromosome system of the ZZ/ZW type in P. hilarii, as well as the correct identification of the Z chromosome in the karyotype. This chromosome displays a segment of terminal heterochromatin in the long arm, similar to the segment observed in the short arm of the W chromosome, also showing a G-banding pattern similar to that of the short arm and part of the long arm of the W chromosome. A hypothesis on the origin of the W chromosome from an ancestral chromosome similar to the Z chromosome is presented.     

A cytogenetic analysis of X- ray induced male steriles on the Y chromosome of Drosophila melanogaster

A total of 1020 B ^s Yy ⁺chromosomes was screened for the induction of male sterile mutations by X irradiation. The 29 recovered mutations were analyzed by genetic complementation and the metaphase chromosomes stained with Hoechst 33258 and observed with fluorescence microscopy. The cytological and genetic maps derived from this analysis were compared to similar maps of the Y chromosome mutations isolated in an earlier study (Brosseau, 1960). Unlike the previous work we have identified only 6 male fertility loci (2 on the short arm, 4 on the long arm) on the Y chromosome. These loci are distributed along the length of the long arm and are likely to reside at two separate sites on the short arm. There is no apparent clustering of these fertility factors in this heterochromatic chromosome. The deletions obtained in this study were observed to be unstable and the nature of this instability was investigated. The original Y chromosome was marked at both telomeres with normally X-linked genes. The loss of one or the other of these markers was accompanied in many cases by the concomitant loss of large segments of Y chromosome material. The possible mechanism of this loss is discussed.Author to whom correspondence should be sent     

Patterns of replication in the neo-sex chromosomes ofDrosophila nasuta albomicans

Drosophila nasuta albomicans (with 2n = 6), contains a pair of metacentric neo-sex chromosomes. Phylogenetically these are products of centric fusion between ancestral sex (X, Y) chromosomes and an autosome (chromosome 3). The polytene chromosome complement of males with a neo-X- and neo-Y-chromosomes has revealed asynchrony in replication between the two arms of the neo-sex chromosomes. The arm which represents the ancestral X-chromosome is faster replicating than the arm which represents ancestral autosome. The latter arm of the neo-sex chromosome is synchronous with other autosomes of the complement. We conclude that one arm of the neo-X/Y is still mimicking the features of an autosome while the other arm has the features of a classical X/Y-chromosome. This X-autosome translocation differs from the other evolutionary X-autosome translocations known in certain species ofDrosophila.     

The genetic control of nucleolus formation in wheat

The wheat variety Chinese Spring has four pairs of nucleolus organisers of known rDNA content. The genetic control of these has been investigated in root tip cells by cytologically scoring the number of nucleoli per cell in (a) aneuploid derivatives each having a different dosage of a particular chromosome or chromosome arm and (b) in substitution lines where nucleolus organiser chromosomes have been replaced by homologues possessing different amounts of rDNA. It has been assumed that nucleolus organiser activity is correlated with nucleolus size and thus with the presence of a cytologically visible nucleolus. Those nucleolus organisers on chromosomes 1A and 5D, which together possess only 10% of the rDNA form a visible nucleolus only infrequently in the presence of the larger nucleolus organisers on chromosomes 1B and 6B. When a major pair of organisers on chromosomes 1B or 6B is deleted, the smaller nucleolus organisers form a visible nucleolus more frequently. Similarly, when the major nucleolus organisers are replaced by organisers with less rDNA, the smaller nucleolus organisers form visible nucleoli more frequently. When a small nucleolus organiser is replaced by one with much more rDNA, a larger nucleolus is formed. These and other findings lead to the general conclusions that there is a frequently, but not invariably, seen correlation between rRNA gene number and nucleolus size. However the relative size of the nucleolus formed depends principally upon the proportion of the total active rRNA genes in the cell which are localised at the nucleolus organiser in question. Varying the dosage of at least 13 non nucleolus organiser chromosomes also resulted in changes in the number of visible nucleoli per cell. This implies the genetic control of individual nucleolus organisers is complex. Inclusion in the wheat genome of the nucleolus organiser chromosome from Aegilops umbellulata, causes suppression of the wheat nucleolus organisers, the Aegilops umbellulata organiser remaining active. This suppression is similar to that observed in many interspecific plant and animal hybrids.     

An N-band marker for gene Lr18 for resistance to leaf rust in wheat

The leaf rust resistance gene, Lr18, of common wheat cultivars has been derived from Triticum timopheevi and is located on chromosome arm 5BL. Chromosome banding (N-banding) analyses revealed that in the wheat cultivars carrying Lr18 that were examined, which had been bred in 6 different countries, chromosome arm 5BL possessed a specific terminal band not carried by their susceptible parental cultivars. It was suggested that this terminal N-band was introduced from T. timopheevi together with Lr18. N-banding analysis of a T. timopheevi strain showed that one of two timopheevi chromosomes had provided Japanese wheat lines containing Lr18 with the terminal band.     

The quantitative analysis of chromosome pairing and chiasma formation based on the relative frequencies of M I configurations. III. Telocentric trisomics

The estimation of the crossing-over potentials of the two arms of a specific chromosome that can not be recognized in the diploid, was earlier found to be inefficient with the use of the primary trisomic. With the telocentric trisomics two groups of two different configurations each can be recognized that permit a reasonably exact estimation of the two parameters. Each telocentric trisomic yields estimates for both arms. The trisomic arm is underestimated as a result of partner-exchange and/or interference by the nucleolus in a nucleolus bearing arm. The other arm is estimated more correctly. Thus the two telocentrics together give a complete picture of the chromosome. After a correction for differences in overall chiasma frequencies the ratio of the crossing-over potentials of the two arms of the satellite chromosome ofSecale cereale was found to be approximately 2. This is large for a submedian chromosome in comparison with the ratio for the genome as a whole and it is attributed tentatively to the nucleolus interfering with chiasma formation in the short arm. It is suggested that the three homologous arms, especially the long arms, differ in respect to the tendency to pair and in chiasma frequency.     

The sex-determining region Y (SRY) gene is mapped to p12-p13 of the Y chromosome in pig (Sus scrofa domestica) by in situ hybridization

The sex-determining region Y is a gene located in the distal portion of the short arm of human (SRY) and mouse (Sry) Y chromosomes and considered to be the best candidate for the testis determining factor (TDF/Tdy). The gene is believed to be the key factor in sex differentiation in mammals and is conserved across mammalian species. We report herein that the SRY/Sry gene has been assigned to pi 2-p13 on the short arm of the Y chromosome in pig by in situ hybridization. The result confirms interspecies conservation of this chromosomal segment in the evolution of mammalian chromosomes, and suggests further use of this gene probe in genomic studies in other mammals. The assignment of the Sry gene is the second physical gene mapping data available for the Y chromosome in pigs. Such data can be used in the effort of constructing the pig gene map and for further establishment of a comparison of sex chromosome morphology in different mammalian species concerning sex-specific and pseudoautosomal regions.     

A chromosome rearrangement in Neurospora that produces segmental aneuploid progeny containing only part of the nucleolus organizer

In translocation T(ILVL)OY321 of Neurospora crassa a distal portion of the nucleolus organizer chromosome, including ribosomal DNA sequences and the nucleolus satellite, is interchanged with a long terminal segment of IL. When OY321 is crossed by Normal sequence, one-fourth of the meiotic products are segmental aneuploids that contain two copies of the long IL segment and that are deficient for the distal portion of the organizer. Each such product forms a nucleolus and is viable. The complementary aneuploid products are deficient for the IL segment and are therefore inviable. — In crosses of OY321xOY321, each product is capable of making two nucleoli; nucleoli formed by the separated nucleolus organizer parts usually fuse, but most 8-spored asci contain some nuclei in which two separate nucleoli can be seen. One nucleolus is then terminal on its chromosome while the second is interstitial and somewhat smaller. — In crosses of OY321 x Normal, half of the meiotic products are capable of making two nucleoli. However, only about 15% of 8-spored asci have one or more nuclei containing separate nucleoli. At pachytene and later in prophase I, the single fusion nucleolus is associated with three bivalent chromosome segments. Each nucleus of every ascus contains at least one nucleolus, even in asci where some nuclei display two nucleoli. — Crosses of Aneuploid x Normal are usually semibarren, producing a reduced number of ascospores, some of which are inviable. Some aneuploid cultures become fully fertile by reverting to a quasinormal sequence lacking a satellite. In some crosses of Aneuploid x Normal, individual asci may show at prophase I either complete loss, partial loss, or pycnosis of the translocated IL segment. This observation of pycnosis suggests chromosome inactivation. — Growth from aneuploid ascospores is initially slow, but can accelerate to the wild-type rate.     

Comparative cytogenetic studies in Sus verrucosus,Sus celebensis and Sus scrofa vittatus (Suidae,Mammalia)

Chromosome studies on the Javan warty pig (Sus verrucosus), the Sulawesi warty pig (S. celebensis) and a subspecies of the wild boar, S. scrofa vittatus, have revealed diploid chromosome numbers of 38. The morphology and C-band size of chromosome 10 are different in S. verrucosus and the two other species. Both S. verrucosus and S. celebensis have a Y chromosome that is larger than the Y chromosome of domestic and wild S. scrofa, and is submetacentric rather than metacentric. There are differences between all three species in the G-banding pattern of the long arm of the Y chromosome. The presence of 2n=38 chromosomes in the Javan warty pig and the Sulawesi warty pig provides new strong evidence that the basic chromosome number in the genus Sus is 38. The differences in karyotype between these pigs (chromosome 10 and the Y chromosome) confirm that they are separate species.     

Nucleolar organizing chromosomes ofRicinus

Summary Pachytene chromosome morphology was compared in nine races ofRicinus communis L. (2n = 20), using pollen mother cells (PMCs) and light microscopy. Of the ten bivalents, only the two possessing nucleolar organizing regions (NORs), chromosomes 2 and 7, exhibit structural variations among the races. The NORs are located in the short arms of these two chromosomes. Most of the observed structural variations affect these short arms, which are similar morphologically and consist largely of heterochromatic segments. The PMCs contain a single nucleolus and this is associated with the NOR of each of the two chromosomes at a particular frequency in each race. In eight races, a nucleolar constriction (NC) is present in either chromosome 2 or chromosome 7. In these races, the nucleolus is associated with the chromosome possessing an NC at a frequency of 100% and with the chromosome lacking an NC at a frequency ranging between 5.6 and 100%, depending upon the race. No microscopically visible NC is present in the ninth race. In this race, the nucleolus is associated with both chromosomes 2 and 7 at a frequency of 100%. The association of the nucleolus with a chromosome possessing an NC is at the NC and with a chromosome lacking an NC is at the terminal heterochromatic segment of the short arm. Several interpretations are offered to account for the variations in frequency of association between the nucleolus and each of the nucleolar organizing chromosomes. It is suggested that the two non-linked NORs have evolved through some intragenomic changes rather than polyploidy, that this species is highly intolerant to structural variations other than those occurring in or near the NORs, and that structural variations in the nucleolar organizing chromosomes are not associated with racial variations in plant phenotype.Paper of the Journal Series, New Jersey Agricultural Experiment Station