Comparative chromosome banding studies in the family Cercopithecidae

Comparative banding studies in eight species of the family Cercopithecidae, subfamily Cercopithecinae allowed us to identify the chromosomes that have been conserved and those that have undergone structural changes. The results suggest that while the ancestral karyotype of the Cercopithecini was probably similar to that ofCercopithecus aethiops, the ancestral complement of the cercopithecinae was probably of the type now found in the Papionini. Thus, after their divergence, one of the groups maintained an extremely stable chromosomal complement (Papionini 2n=42) while the other underwent extreme chromosomal rearrangements (Cercopithecini 2n=48–72).     

Supernumerary chromosomal elements in lymphocytes cultured from phenotypically normal human adult males

In a group of phenotypically normal men there were approximately 0.24% of metaphase lymphocytes with extra chromosomal elements along with the regular 46 chromosomes. They ranged in size from small acrocentric-acentric elements to elements longer than any chromosome arm. These elements have been referred to as supernumerary chromosomal elements. No significant effects due to donor's age, smoking history, season, storage of blood samples prior to culture, or culture medium, were found either in the frequency of supernumerary elements per cell or in the frequency of cells with supernumerary elements. Furthermore, the same subject did not consistently exhibit supernumerary elements. Furthermore, the same subject did not consistently exhibit supernumerary elements when sampled during four successive quarters of the year. Some of these elements in pairs were identified by G-banding technique as translocation chromosomes bearing long arms of chromosome number 2 and presumptive short arms of chromosome 8, acentric long arms of chromosome 4, and iso-acentric chromosomes for the long arms of chromosome 5. Presumably, more than one type of cytogenetic event occurred in their formation. Circumstantial evidence has been presented to show that the means of elimination of these supernumerary elements is a process of chromosomal disintegration.     

Molecular characterization and chromosomal localization of two families of satellite DNA in Prochilodus lineatus (Pisces,Prochilodontidae), a species with B chromosomes

Prochilodus lineatus, an abundant species in the Mogi-Guaçu river basin, represents a large part of the region's fishing potential. Karyotypic analyses based on classic cytogenetic techniques have revealed the presence of 54 meta-submetacentric type chromosomes, together with the occurrence of small supernumerary chromosomes with intra and interindividual variations. This paper describes the genomic organization of two families of satellite DNA in the P. lineatus genome. The chromosomal localization these two repetitive DNA families through fluorescence in situ hybridization (FISH) demonstrated that the SATH1 satellite DNA family, composed of approximately 900 bp, was located in the pericentromeric region of a group of chromosomes of the standard complement, as well as on all the B chromosomes. The SATH2 satellite family has a monomeric unit of 441 bp and was located in the pericentromeric regions of some chromosomes of the standard complement, but was absent in the B chromosomes. Double FISH analyses showed that these two families participate jointly in the pericentromeric organization of several chromosomes of this species. The data obtained in this study support the hypothesis that the B chromosomes derive from chromosomes of the standard complement, which are carriers of the SATH1 satellite DNA.     

Congenital anomalies and developmental delay in a boy with double chromosome 6 derived supernumerary marker

The frequency of small supernumerary marker chromosomes has been estimated to approximately 0.45 per 1000 newborns. They are usually seen as single marker chromosomes in a mosaic state. Two cytogenetically identical markers have been observed only occasionally. We report on a boy, with congenital heart defect, neonatal hypotonia, hypogenitalism, delayed psychomotor development and mild dysmorphic facial features. The GTG karyotype performed on peripheral blood lymphocytes revealed a mosaic male karyotype with three cell lines. One cell line had a normal karyotype. In the other two either single or double chromosome 6 derived supernumerary markers were present, leading to partial trisomy or partial tetrasomy of chromosome 6, respectively.     

Unusual supernumerary chromosomes: types encountered in a referred population,and high incidence of associated maternal chromosome abnormalities

Summary In a 6-year period 128 patients with supernumerary autosomes were identified in our laboratory. The majority had primary trisomy, but 19 (15%) had extra, unusual chromosomes, not just a normal chromosome present in an extra copy. Of these, 18 were complex and did not resemble any one part of the standard chromosome complement. There was a preponderance of females among the 19 cases. Chromosome analysis of the parents in the 14 most recent cases revealed maternal chromosome abnormalities in 11 (79%). Of these 11, eight mothers had balanced reciprocal translocations; nondisjunction led to the smaller of their translocation chromosomes being passed on as the supernumerary chromosome in their offspring. Thus, nondisjunction of maternal translocations accounts for a major proportion of the unusual supernumerary chromosomes found by our laboratory. Advanced maternal age was noted in this group of mothers. Three mothers had supernumerary chromosomes themselves. We conclude that unusual supernumerary chromosomes (1) are not rare among patients referred for chromosome studies; (2) are generally not simple products of breakage; (3) are very frequently the result of malsegregation of a balanced maternal reciprocal translocation; and (4) are very difficult to characterize unless a balanced parental translocation is identified. Parental karyotypes should be obtained whenever a patient has an extra, unusual chromosome.     

DNA replication,G- and C-bands and meiotic behaviour of supernumerary chromosomes of Rattus rattus (Linn.)

Supernumerary chromosomes have been observed in a few individuals of three subspecies of Rattus rattus from India and Nepal. The supernumerary chromosomes are late replicating and positively heteropycnotic during meiosis which characterize their heterochromatic nature. Their G-banding patterns do not exactly resemble the patterns exhibited by the chromosomes of similar size and morphology of the normal complement. The supernumerary chromosomes become conspicuous for the lack of a centromeric C-band in them as compared to the prominent C-bands in other chromosomes of the complement.     

The evolution of double fertilization and endosperm: an ”historical” perspective

 One hundred years ago, the developmental origin of endosperm from double fertilization was discovered independently by Navashin and Guignard. For much of the twentieth century, specific events related to the evolutionary origin of the endosperm of flowering plants remained a mystery. However, during the past 20 years, advances in phylogenetic reconstruction of seed plants, genetic theory associated with kin selection, and comparative study of the reproductive biology of the closest living relatives of angiosperms (Gnetales) have advanced our understanding of the evolutionary events associated with the origin of double fertilization and endosperm. Recent developmental analyses of Ephedra and Gnetum (members of Gnetales) indicate that these nonflowering seed plants undergo a regular process of double fertilization that yields two diploid zygotes. Use of explicit genetic and developmental criteria for analysis of evolutionary homology demonstrates congruence with the hypothesis that double fertilization processes in Gnetales and angiosperms were inherited from a common ancestor of the two lineages. In its rudimentary form, the second fertilization event in the ancestors of flowering plants yielded a supernumerary diploid embryo that was genetically identical to the normal embryo, a process most similar to what occurs in extant Ephedra. Subsequent to the divergence of the angiosperm stem lineage, the supernumerary embryo derived from double fertilization was developmentally modified into an embryo-nourishing structure, endosperm, that now characterizes angiosperms. Received: 25 September 1997 / Accepted: 3 November 1997     

Effects of microwaves on the puffing pattern of <Emphasis Type="Italic">D. melanogaster</Emphasis>

The influence of electromagnetic field exposure on puffing pattern of salivary gland polythene chromosomes, viability and fertility of Drosophila melanogaster of the wild type Canton-S line was studied. Experimental conditions: Electromagnetic field characteristics: frequency — 36.64 GHz, power density — 0.4 W/m², exposure time −10 seconds. Electromagnetic field exposure was conducted on the egg stage. Results: in larvae developed from the exposed eggs 3 of 8 chromosomal puffs tested (71CE, 82EF, and 83E) had significantly smaller dimensions than these in control at the prepupal stage. Viability of Drosophila estimated by the number of adult flies hatched from exposed eggs decreased, while the number of dominant lethal mutations increased. Conclusion: the exposure to a low-level microwave irradiation suppressed puffing activity at ecdysone-inducible loci of Drosophila polythene chromosomes, increased frequency of dominant lethal mutations and decreased Drosophila viability but did not influence Drosophila fertility.     

Supernumerary chromosome variation and heterochromatin distribution in the endemic New Zealand frog Leiopelma hochstetteri

Specimens of the endemic New Zealand frog Leiopelma hochstetteri from Tapu on North Island were found to have six, nine or ten supernumerary chromosomes in their karyotypes. In comparison with previously published data, these results further indicate probable geographic variation in supernumerary chromosome number between populations. Increased numbers of supernumeraries in these frogs is correlated with apparent decrease of centromeric heterochromatin in the five large metacentric chromosomes of the karyotype, as detected by C-banding. Meiosis was abnormal in a male with a high number of supernumeraries. In lampbrush preparations from a single female with one supernumerary univalent, the supernumerary often had a denser, beaded appearance in comparison with the regular bivalents. Evidence is consistent with the notion that these supernumerary chromosomes may have arisen from centromeric fragments.     

Axillary shoot proliferation and in vitro flowering in an adult giant bamboo, Dendrocalamus giganteus Wall. Ex Munro

Summary Continuous axillary shoot proliferation and in vitro flowering were achieved using single node explants from a mature (over 70-yr-old) field clump of Dendrocalamus giganteus (giant bamboo). The shoots proliferated in a basal Murashige and Skoog medium with 6 mgl⁻¹ (26.6 μM) N⁶-benzyladenine (BA) and 2% sucrose. The rate of shoot proliferation gradually increased to over three-fold before in vitro flowering took place. In vitro flowering was not the expression of a species-specific mechanism believed to occur during gregarious flowering, as the mother clump did not flower. The rate of shoot proliferation decreased at flowering, accompanied by reversion of flowering. The development of axillary meristems into vegetative or generative shoots depended on the level of BA. The possible role of BA, changes in the rate of shoot proliferation decreased at flowering, accompanied by reversion of flowering. The development of axillary meristems into vegetative or generative shoots depended on the level of BA. The possible role of BA, changes in the rate of shoot proliferation leading to build up, and release of stress in relation to flowering and its reversion are discussed.     

Karyotypic diversity in polyploid gibel carp,Carassius auratus gibelio Bloch

Polyploid gibel carp, Carassius auratus gibelio, is an excellent model system for evolutionary genetics owing to its specific genetic background and reproductive modes. Comparative karyotype studies were performed in three cultured clones, one artificially manipulated group, and one mated group between two clones. Both the clones A and P had 156 chromosomes in their karyotypes, with 36 metacentric, 54 submetacentric, 36 subtelocentric, 24 acrocentric, and six small chromosomes. The karyotype of clone D contained 162 chromosomes, with 42 metacentric, 54 submetacentric, 36 subtelocentric, 24 acrocentric, and six small chromosomes. All the three clones had six small chromosomes in common. Group G, being originated from the clone D by artificial manipulation, showed supernumerary microchromosomes or chromosomal fragments, in addition to the normal chromosome complement that was identical to the clone D. The offspring from mating between clones D and A had 159 chromosomes. Comparing with the clone A, the DA offspring showed three extra metacentric chromosomes. In addition, variable RAPD fingerprint patterns and unusual SCAR marker inheritance were, respectively, detected among individuals of artificial group G and in the mated DA offspring. Both the chromosome and molecular findings suggest that genome reshuffling might have occurred by manipulation or mating of the clones.     

The evolution of embryogeny in seed plants and the developmental origin and early history of endosperm

For almost a century, the formation of endosperm from a second and distinctive fertilization event has been viewed as a unique feature of flowering plants. However, until recently, the evolutionary origin of this unique embryo-nourishing entity remained a mystery. Based upon comparative developmental analysis of reproduction among basal angiosperms and their closest extant relatives, the Gnetales (Ephedra, Gnetum, and Welwitschia), it is possible to construct an explicit hypothesis of the events that led to the evolutionary establishment of double fertilization and endosperm. The formulation of this historical record is derived entirely from and dependent upon the determination of reproductive features that are likely to have characterized the common ancestors of angiosperms and Gnetales. Current evidence is most congruent with the concept that a process of double fertilization first evolved in a common ancestor of the Gnetales and angiosperms. Initially, however, the second fertilization product was diploid and yielded a supernumerary embryo. Subsequent to the divergence of the angiosperm lineage from its closest relatives (which include the Gnetales), modification of the development of the supernumerary embryo (derived from the second fertilization event) led to the establishment of an embryo-nourishing endosperm. Comparative analysis of patterns of embryogeny within Gnetales and angiosperms establishes that embryo development in the ancestors of flowering plants (with a rudimentary process of double fertilization) was ab initio cellular, and not free nuclear, as had previously been assumed. Thus, it is likely that the earliest flowering plants displayed an ab initio cellular pattern of endosperm development, whose expression was inherited from that of the supernumerary embryo of the ancestors of flowering plants.     

Supernumerary chromosomes in the second outbreeding species of the wheat group

Meiosis was examined in PMC of 138 plants of the outbreeder Triticum speltoides (=Aegilops speltoides) and 175 plants of the closely related T. longissimum (= Ae. longissima), which is a selfer. Nine of the T. speltoides plants, originating fra two of the five Israeli populations under study, contained B chromosomes in addition to the normal complements (2n = 14). No supernumerary chromosomes were found in T. longissimum. — Plants were found carrying 1, 2 or 3 B chromosomes, which seem to be stable among PMC. Their size is 2/3 of the average length of the regular chromosomes, but otherwise they are similar in appearance. Pairing between Bs is common as bivalents and trivalents, but whether this association is ehiasmatic is not clear. There is a slight reduction in chiasma frequency of the regular complement in B-carriers compared to other plants from the same population. — The only other species in the wheat group reported to have B chromosomes in natural populations is also an outbreeder, namely T. tripsacoides (=Ae. mutica). The connection between outbreeding and B chromosomes might be significant.     

Parallel mosaicism of supernumerary chromosomes and sex chromosomes in Echymipera kalabu (Marsupialia)

Echymipera kalabu (Peramelidae: Marsupialia) does not have the full chromosome complement in all its adult somatic tissues. The chromosomes missing are the Y-chromosome in the male and an X-chromosome in the female. The full complement is present in the corneal epithelium and the reproductive tissue. A parallel mosaicism to this exists with respect to small supernumerary chromosomes which are found in certain animals of this species. These supernumeraries must be subject to the same control system as that which is responsible for the elimination of the sex chromosomes.     

Frequency,origin, and survival of aneuploids in tetraploid ryegrass

Aneuploids with 26 to 30 chromosomes occurred in progenies of induced tetraploids of Lolium perenne in a frequency of 6 to 23% in C₁ families, 12% in C₂ and 6% in advanced generations. The most frequent types had 27 and 29 chromosomes. Most were apparently recovered through female transmission, which varied for aneuploid gametes with different chromosome numbers and which probably depended on the chromosome involved. In general, aneuploids showed a reduction in fertility. Even with the same chromosome number, fertility varied perhaps as a result of differences between the chromosomes involved. Aneuploids could not be distinguished from eu-tetraploids on a morphological basis. Tetraploids late and early in respect to flowering did not differ in aneuploid frequency. No reversion to diploidy was observed in successive generations.     

Biotypic differences in the karyology ofPennisetum pedicellatum Trin

Detailed karyological analyses have been made of the five biotypes ofPennisetum pedicellatum Trin. These biotypes not only differ in some morphological traits but also in their chromosomal characteristics. Biotype-B with 2n = 48 chromosomes shows constancy, while in the other four 2n = 36 and 64 are found to be “floating”. Other numerical variations include 2n = 42 and 18 chromosomes. Minute karyological differences are not only noted amongst the biotypes, but also there are variations in the complements within a biotype. Such variations are presumed to be buffered through the apomictic mode of reproduction. From the morphological and cytological studies, the possibility of separation of biotype-B from the complex in future has been envisaged.     

Dosage effect of a gene with a regulating effect on anthocyanin synthesis in a trisomic Petunia hybrida

A Petunia hybrida inbred line (W 28) has white flowers with red spots on the corolla. These spots are the result of back mutations of an unstable allele of the gene Anl for anthocyanin synthesis. Among the progeny of a population of selfed plants a primary trisomic with red-spotted white flowers was found. The reversion frequency was more than twice as high as compared with disomic plants of the same family.It was found that the chromosome in triplicate was not the chromosome on which the gene Anl is localized. It can be concluded that there is an independently segregating factor which influences the frequency of back mutations of the Anl locus. Twin spots were found among the flowers of the trisomic. They consisted of two adjacent sectors, one with a spot frequency equal to that of the flowers of disomic plants, and the other with a spot frequency more than twice as high as that of the trisomic. Probably an irregular distribution of the extra chromosome resulted in one sector with the normal diploid number of chromosomes, and an adjacent sector with two extra chromosomes. The reversion frequencies in the sector suggest that the factor which affects the reversion frequency of the unstable alleles of Anl exhibits a dosage effect.     

A comparative study of mitotic and meiotic chromosomes of the Montandon's newt,Triturus montandoni (Urodela: Salamandridae) from Poland and Rumania

A karyological analysis was carried out on two populations ofTriturus montandoni, one from Poland and another from Rumania. For both samples, morphometric characteristics and C-banding pattern of mitotic chromosomes are provided. Only slight differences between specimens from two geographic localities were found. Data on chiasma frequency and distribution are presented for male meiosis. No sex-related heteromorphism was found and for none of the chromosomal arms was a consistent absence of chiasmata recorded. There was a relatively high proportion of spermatocyte metaphases I with chiasmata on both arms of all chromosomes in all specimens studied. It is concluded that there are no well-defined sex chromosomes in the chromosomal complement of the maleT. montandoni. The findings are compared with previous studies on chromosome morphology, C-banding pattern, and meiosis in closely related species,T. vulgaris andT. helveticus.     

Cytogenetic evaluation of 163 azoospermics

A constitutional chromosomal aberration was diagnosed in 38/163 (23.3%) azoospermic patients. Whereas the 47,XXY complement was the commonest (31/38 cases), the following abnormal karyotypes were also found: 46,XX; 46,X,del(Y) (q11); 46,X,r(Y); 46,XY,inv(1) (p3500q21.3)mat; and 46,Y,t(X;3) (q26;q13.2)mat (both the deleted and the annular Y were observed twice). Pooled data from the literature showed that the frequency of chromosomal abnormalities is higher in azoospermic (150.4/1000) than in infertile (55.3/1000) males, which in turn is higher than in newborns (less than 6/1000). The observed different frequency between azoospermic and infertile individuals is given by several types of chromosomal abnormalities, mainly by the complement 47,XXY. The analysis also showed that the male infertility secondary to rob translocations and supernumerary marker chromosomes is usually not related to azoospermia. The contrary occurs in certain rcp and gonosome;autosome translocations and in autosome inversions.     

In situ expression of the GmNMH7 gene is photoperiod-dependent in a unique soybean (Glycine max [L.] Merr.) flowering reversion system

Soybean is a short-day plant and its flowering process can be reversed when switching from short-day to long-day conditions. Flowering reversion provides a useful system to study the flowering process in both forward and backward directions. In this study, we optimized a soybean flowering reversion system using a photoperiod-sensitive cultivar Zigongdongdou. Three types of terminal structures were found during flowering reversion: reversed terminal raceme (RTR), short terminal raceme (STR), and vegetative terminal (VT). The relative frequency of these terminal structures during flowering reversion under long day was dependent on the duration of the prior short day (SD) pretreatment. This process is phytochrome dependent and young plants were more susceptible to flowering reversion. Leaf removal increased the minimal SD period needed for the induction of STR. To demonstrate the application of this system, we studied the patterns of in situ expression of the GmNMH7 gene during flowering development and reversion. NMH7 family members encode MADS-box proteins and are unique in legume families since their expression can be detected in both developing flowers and nodules. In situ hybridization experiments using plants grown under different photoperiod cycles provided several lines of evidence supporting a close relationship between GmNMH7 gene expression and floral development in soybean. Furthermore, it seems that GmNMH7 may participate in flower development at different stages. Interestingly, the expression pattern of GmNMH7 in root nodules was also found to be regulated by photoperiod. These results support the notion that the photoperiod sensitive GmNMH7 gene may play multiple roles in growth and development in soybean.C. Wu and Q. Ma contributed equally to this work.