大苞萱草染色体的核型分析

对大苞萱草体细胞染色体计数,并对其核型进行分析,结果表明:大苞萱草的染色体数目为 2n=22;核型公式为2n=2x=22=10m 6sm 4st 2T,染色体相对长度组成为2n=22=4L 6M2 10M1 2S, 属于2A型。全组染色体总长31．26μm,长臂总长为21．05μm,核型不对称系数为67．34％。     

Variation in the karyotype of three cultivars of Narcissus tazetta L. (Amaryllidaceae)

Three cultivated varieties of Narcissus tazetta, Grand Soleil d'Or, Chinese Sacred Lily and Cypri, are triploid (2n = 3x+30) with the basic number 10. Grand Soleil d'Or has three homomorphic sets, each comprising 2 long submetacentrics, 4 long acrocentrics and 4 short acrocentrics. Karyotypes of the other two varieties are heteromorphic. Both possess one telocentric satellited chromosome. In addition, Cypri shows translocation between two chromosomes belonging to the seventh and eighth triplets. The number of secondary constrictions varies between 3 (Chinese Sacred Lily) and 4 (Grand Soleil d'Or and Cypri) which is also the number of nucleoli observed in the respective varieties.     

Variation in the electrophoretic karyotype analysed by the assignment of DNA probes in Candida albicans

By using pulsed-field gel electrophoresis, we have separated the entire chromosome bands and examined the electrophoretic karyotypes of 27 strains of Candida albicans. The electrophoretic karyotype varied widely among these strains. Their chromosomal DNAs were resolved into 7-12 bands ranging in size from 0.42 to 3.0 Mb. Most of the separated chromosomal bands were assigned by eight cloned C. albicans DNA probes. These results suggest that the haploid number of C. albicans chromosomes is eight. Each of the probes hybridized specifically to one or two bands of similar size in most strains. With the exception of the MGL1 probe, when two bands were detected by one probe, the size of one of them was very conserved whilst the other was of fairly variable size. The sizes of the chromosome bands assigned by the MGL1 probe were much more variable. As C. albicans is considered to be a diploid organism, it is inferred that the karyotype polymorphism between strains is mainly derived from wide size heterogeneity in one of the homologous chromosomes. Furthermore, we have confirmed species-specific and strain-specific variation in medically important Candida species (C. stellatoidea, C. tropicalis, C. parapsilosis, C. krusei, C. guilliermondii, C. kefyr and C. glabrata). Electrophoretic karyotype analysis is thus useful for species assignation. The TUB2 probe, encoding C. albicans beta-tubulin, hybridized to the chromosomal DNA of all the Candida species examined, but four C. albicans probes exhibited cross-species hybridization with C. stellatoidea only. The karyotype of C. stellatoidea seems to be within the range of the intraspecies variation observed in C. albicans.     

Isolation of polymorphic microsatellite loci in Hemerocallis fulva and Hemerocallis citrina (Hemerocallidaceae)

Twenty microsatellite loci were isolated from a hybrid of two daylilies, Hemerocallis fulva and Hemerocallis citrina. We characterized individuals from two H. fulva populations and two H. citrina populations in Japan and observed three to 20 alleles per locus in H. fulva and one to 19 alleles per locus in H. citrina. Mean observed heterozygosity within populations ranged from 0.35 to 0.85 in H. fulva and from 0 to 0.95 in H. citrina. In about a half of the loci, the observed heterozygosity did not deviate from Hardy–Weinberg equilibrium. These loci are proved useful in studying gene flow and qualitative trait loci mapping using the two species.     

Oligohydramnios syndrome and XYY karyotype.

A case of oligohydramnios syndrome was found to have an XYY karyotype and an inherited 9qh inversion. It is suggested that normal and extra Y chromosomes are a predisposing factor in the aetiology of severe congenital renal anomalies.     

Factors affecting flow karyotype resolution.

BACKGROUND: One of the major factors which influences the chromosome purity achievable particularly during high speed sorting is the analytical resolution of individual chromosome peaks in the flow karyotype, as well as the amount of debris and fragmented chromosomes. We have investigated the factors involved in the preparation of chromosome suspensions that influence karyotype resolution. METHODS: Chromosomes were isolated from various human and animal cell types using a series of polyamine buffer isolation protocols modified with respect to pH, salt concentration, and chromosome staining time. Each preparation was analyzed on a MoFlo sorter (DAKO) configured for high speed sorting and the resolution of the flow karyotypes compared. RESULTS: High resolution flow cytometric data was obtained with chromosomes optimally isolated using hypotonic solution buffered at pH 8.0 and polyamine isolation buffer (with NaCl excluded) between pH 7.50 and 8.0. Extending staining time to more than 8 h with chromosome suspensions isolated from cell lines subjected to sufficient metaphase arrest times gave the best result with the lowest percentage of debris generated, tighter chromosome peaks with overall lower coefficients of variation, and a 1- to 5-fold increase in the yield of isolated chromosomes. CONCLUSIONS: Optimization of buffer pH and the length of staining improved karyotype resolution particularly for larger chromosomes and reduced the presence of chromosome fragments (debris). However, the most interesting and surprising finding was that the exclusion of NaCl in PAB buffer improved the yield and resolution of larger chromosomes.     

Post-pollination reproductive isolation between diurnally and nocturnally flowering daylilies, Hemerocallis fulva and Hemerocallis citrina

To examine whether floral and post-pollination isolation develops independently or not, we conducted a crossing experiment between Hemerocallis fulva and Hemerocallis citrina that shows large floral divergence adapted for diurnal and nocturnal pollinators that have been believed to be fully cross-fertile. Flowers of the two species from sympatric populations were hand-pollinated with conspecific pollen from the same population (control), interspecific pollen from the same area (sympatric cross), and interspecific pollen from the different area (allopatric cross). After capsule dehiscence, the fruit set, seed set per fruit and seed set per flower were determined among three cross categories. The seed sets per flower were 32 and 77% lower in sympatric and allopatric crosses than in the control when H. fulva was the pollen recipient. There was no difference in three reproductive measures among the cross categories when H. citrina was the pollen recipient. This finding indicates that post-pollination isolation does exist between H. fulva and H. citrina, although it is partial, asymmetric, and weakened in sympatry. Our result suggests that floral and post-pollination isolation may develop independently, and reinforcement may not be a general phenomenon in plants.     

An electrophoretic karyotype of Neurospora crassa.

A molecular karyotype of Neurospora crassa was obtained by using an alternating-field gel electrophoresis system which employs contour-clamped homogeneous electric fields. The migration of all seven N. crassa chromosomal DNAs was defined, and five of the seven molecules were separated from one another. The estimated sizes of these molecules, based on their migration relative to Schizosaccharomyces pombe chromosomal DNA molecules, are 4 to 12.6 megabases. The seven linkage groups were correlated with specific chromosomal DNA bands by hybridizing transfers of contour-clamped homogeneous electric field gels with radioactive probes specific to each linkage group. The mobilities of minichromosomal DNAs generated from translocation strains were also examined. The methods used for preparation of chromosomal DNA molecules and the conditions for their separation should be applicable to other filamentous fungi.     

The karyotype and ploidy of Trypanosoma cruzi.

Little is known of the number or organization of chromosomes in Trypanosoma cruzi, the protozoan parasite responsible for Chagas' disease in man in the New World. Straightforward cytogenetic analysis is precluded because trypanosome chromosomes fail to condense during the cell cycle. We have size-fractionated the chromosome-sized DNA molecules of representative T. cruzi strains by pulsed field gradient (PFG) gel electrophoresis and located several housekeeping genes by Southern blotting using cDNA probes from the related trypanosome T. brucei. We show that DNA molecules from homologous chromosomes of T. cruzi migrate differently in the PFG system and infer that T. cruzi epimastigotes are at minimum diploid. In contrast to T. brucei, mini-chromosomes are absent in T. cruzi. All the housekeeping genes studied hybridize to DNA molecules which can be resolved in the PFG system, suggesting that T. cruzi may have no chromosomes larger than a few megabase pairs.     

Variation of flower opening and closing times in F1 and F2 hybrids of daylily (Hemerocallis fulva; Hemerocallidaceae) and nightlily (H. citrina)

In flowering plants, pollination success is strongly dependent on the timing of when flowers start to bloom and when they start to close. To elucidate the genetic mechanism influencing the timing of flower opening and closing, we obtained F1 and F2 hybrids of Hemerocallis fulva (a diurnally blooming species, pollinated by swallowtail butterflies) and H. citrina (a nocturnally blooming species, pollinated by nocturnal hawkmoths) and observed their flowering behavior from blooming to closing with the use of digital cameras. For flower opening times, F1 hybrids were highly variable, and F2 hybrids showed a bimodal distribution of flower opening times with peaks in both the morning and evening. The ratio of morning flowering and evening flowering among F2 hybrids did not deviate from 1:1. For the start to close time, both F1 and F2 hybrids were similar in showing the major peak in the evening. The ratio of evening closing and morning closing among F2 hybrids did not deviate from 3:1. These results suggest that the time of flower opening and the start of closing are regulated by different major genes.     

Human karyotype polymorphism

Summary In the article the results of a parallel routine and fluorescent investigation of chromosomes in 103 normal individuals (51 women and 52 men) are presented. There were no gross chromosomal abnormalities in the individuals studied, but in 30 (29.1%) of them various autosomal variants (1q+, 9q+, 16q+, 17ph+, Dp+, Gp+, et al.) were detected by the routine method. Five men (9.5%) had Y chromosome variants. The authors were successful in identifyng practically all these chromosomal variant by their fluorescent banding patterns. The occurrence of brilliant fluorescent bands in chromosome parts showing variable fluorescence (paracentromeric area of chromosome 3, short arms and satellites of acrocentric chromosomes and the distal part of Y chromosome) was also investigated. Some questions connected with karyotype polymorphism in man are discussed.

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Zusammenfassung Die Ergebnisse einer Chromosomenuntersuchung mit konventionellen Methoden einerseits und mit der Fluorescenzmethode andererseits bei 103 Normalpersonen (51 Frauen, 52 M?nner) werden vorgelegt. Die untersuchten Personen zeigten keine st?rkeren Chromosomen-Anomalien; 30 (29,1%) zeigten jedoch verschiedene autosomale Varianten (1q+, 9q+, 16q+, 17ph+, Dp+, Gp+, u.a.), die mit konventionellen Methoden entdeckt werden konnten. Fünf M?nner (9,5%) zeigten Varianten des Y-Chromosoms. Praktisch alle diese Varianten konnten auch mit Hilfe der Fluorescenztechnik identifiziert werden. Daneben wurde das Vorkommen brillanter Fluorescenzbanden in Chromosomen, die eine variable Fluorescenz zeigen, untersucht (parazentrischer Bereich des Chromosoms 3; kurze Arme und Satelliten der akrozentrischen Chromosomen; distaler Teil des Y-Chromosoms 3; kurze Arme und Satelliten der akrozentrischen Chromosomen; distaler Teil des Y-Chromosoms). Einige Fragen im Zusammenhang mit dem Polymorphismus des Karyotyps beim Menschen werden diskutiert.

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This investigation is partly supported by the WHO grant HG-70/9684148/23.     

Mammalian karyotype evolution

The chromosome complements (karyotypes) of animals display a great diversity in number and morphology. Against this background, the genomes of all species are remarkably conserved, not only in transcribed sequences, but also in some chromosome-specific non-coding sequences and in gene order. A close examination with chromosome painting shows that this conservation can be resolved into small numbers of large chromosomal segments. Rearrangement of these segments into different combinations explains much of the observed diversity in species karyotypes. Here we discuss how these rearrangements come about, and show how their analysis can determine the evolutionary relationships of all mammals and their descent from a common ancestor.