The mobile nature of acrocentric elements illustrated by three unusual chromosome variants

Variant chromosomes are polymorphic in areas that are rich in repeat sequences such as the pericentromeric regions or in the acrocentric short arm regions. The dynamic nature of these regions is evident in the polymorphisms they exhibit. In this paper three unusual variants are described: a chromosome 21 with additional material on its short arm, a chromosome 7 with an insertion in the short arm and a chromosome 2 with satellites at the end of the long arm. All three variants were shown to involve acrocentric elements using special banding techniques and fluorescence in situ hybridization. The 21 variant was found to be a tricentric with a 21 and two 15 alpha-, two classical and three acrocentric beta-satellite signals interspersed by AgNOR-positive regions. The telomeres were present at the two terminal ends. The insertion on chromosome 7 was found to be C-band positive and to contain acrocentric beta-satellite DNA. However, acrocentric alpha-satellite, classical satellite, whole-chromosome-painting or all-telomeres sequence probes did not hybridize to the insertion. The satellited region of chromosome 2 had two C-bands, a small positive all-centromeres probe signal, and two signals for the beta-satellite probe. Sandwiched between the beta-satellite sequences was an AgNOR-positive region. The telomeres were present at the two ends of the satellited chromosome 2. Chromosome 2 subtelomeric probes hybridized to the terminal ends of the short and long arm of chromosome 2. The common thread in these three variants is the involvement of acrocentric short arm elements. The acrocentric short arm elements are shown to move to other acrocentric or nonacrocentric chromosomes and relocate to both terminal and interstitial positions. The integrations are stable and heritable. Received: 23 September 1997 / Accepted: 23 February 1998     

Novel C-banding patterns in Paragonimus ohirai (Trematoda: Platyhelminthes)

The C-banding pattern for the karyotype of Paragonimus ohirai representing individuals in a new population is reported. The short arm of chromosome 4 consisted of a large pericentromeric proximal C-band block and euchromatic tip. This pattern has not been observed previously and is designated as type E. Other new observations were: chromosome 5 was composed of pericentromeric heterochromatin, a lightly stained intercalary band at the middle portion of the short arm, and a lightly stained interstitial band at the terminal region of the long arm. Chromosome 7 consisted of pericentromeric heterochromatin and a lightly stained telomeric band at the short arm.     

大鳞副泥鳅ZZ/ZW型性别决定的细胞遗传学证据

大鳞副泥鳅是鲤形目、鳅科的鱼类。其2n数为48,核型组成为12m+4sm+32 t(雄性),11m+5sm+32t(雌性)。根据银染带和C带特征分析,证实大鳞副泥鳅为ZZ/ZW型性别决定。Z染色体为中部着丝粒染色体,在其长臂端部有Ag -NOR存在。 W染色体为亚中部着丝粒染色体,在其长臂末端也有Ag-NOR存在,同时还有一深染的居间C带,这是W染色体独有的带纹特征。 Abstract:Paramisgurnus dabryanus belongs to Cypriniformes,Cobitidae.Its 2n is 48.The karyotype formula is 12m+4sm+32t(in male),11m+5sm+32t(in female).According to the Ag-NORs band and C-band patterns,we consider that its sex determination is of ZZ/ZW type.The Z chromosome is a metacentric one with Ag-NORs located on its arm end.The W chromosome is a submetacentric with Ag-NORs located on the terminal of its long arm.There is a darkly stained C-band on the long arm of W chromosome.This band is a characteric of the W chromosome.     

Molecular evidence of Y-autosomal translocations in owl monkeys

Probe pDP1007, which contains highly conserved DNA sequences from the sex-determining region of the human Y chromosome, cross-hybridized with owl monkey EcoRI restriction fragments of 1.8 kb and 6.6 kb. Southern transfer analysis of owl monkey (karyotype VI)--rodent somatic cell hybrids localized the 1.8-kb fragment on the owl monkey X chromosome and the 6.6-kb fragment, which is male specific, on chromosome 14/Y. Regional in situ chromosome mapping of pDP1007 revealed specific sites of hybridization: the distal short arm of the X chromosome of karyotypes IV, VI, and VII; the small metacentric Y of karyotype IV; the C-band positive region on the short arm of chromosome 17/Y (karyotype VII); and the C-band positive region on the long arm of chromosome 14/Y (karyotype VI). These molecular findings reinforce cytological evidence that Y-chromosomal material has been transferred to autosomes 14 and 17 in owl monkeys of karyotypes VI and VII, respectively, in which there are no independently segregating Y chromosomes.     

石貂的染色体研究

本文对分布在我国的石貂北方亚种染色体进行了较详细的研究。结果表明２ｎ＝３８,核型为１４（Ｍ）＋４（ＳＭ）＋１８（ＳＴ）,ＸＹ（Ｍ,Ａ）。Ｃ－带显示该亚种的一些染色体着丝粒区域结构异染色质弱化或消失。Ｎｏ,９染色体的短臂完全异染色质化;Ｘ染色体长臂丰出现插入杂色质带;Ｙ为完全结构异染色质组成。     

A new variant of chromosome 16

Summary A new variant of chromosome 16 with an additional C-band negative segment in the proximal region of the short arm is described. This variant chromosome was found in four cases, two of which were detected prenatally. In three probands the variant chromosome 16 was inherited from a phenotypically normal father.     

Cytogenetic analysis of some Brazilian marsupials (Didelphidae: Marsupialia)

Three species of marsupials from the Amazon region (Marmosa cinerea, Caluromys lanatus, and Didelphis marsupialis) and two from the region of S?o Paulo (Didelphis marsupialis and Didelphis albiventris) were studied. The G-banding pattern of the species with 2n = 14 (M. cinerea and C. lanatus) was very similar, as well as the pattern of G-bands in the species with 22 chromosomes (Didelphis). All of the autosomes of M. cinerea and D. albiventris have centromeric C-bands and the Y chromosome is totally C-band positive. The long arm of the M. cinerea X chromosome is completely C-band positive except for a negative band close to the centromeric region. In D. albiventris the long arm of the X chromosome is C-band positive except for a negative band close to the telomeric region. In M. cinerea the silver-stained nucleolar organizer regions (Ag-NORs) are found in the acrocentric chromosomes, being located in the telomeric region of one pair and in the centromeric region of the other pair. Caluromys lanatus has centromeric Ag-NORs in one acrocentric and in one submetacentric chromosome pairs. Didelphis marsupialis has three chromosome pairs with telomeric Ag-NORs. In D. albiventris the Ag-NORs are terminal and located in both arms of one pair and in the long arm of two pairs of chromosomes.     

鼷鹿云南亚种（Tragulus javanicus williamsoni）的核型分析

本文以染色体分带技术,发现鼷鹿云南亚种的染色体数目为2n=32。全部为双胃染色体,NF=64。所有染色体着丝点区分布有C带,多数染色体的端部或两端也有C带。某些染色体还有插入C带。Y染色体C带阳性,有一Ag-NORs。文章对鼷鹿云南亚种染色体独特的C带分布以及和核型进化的关系进行了讨论。     

Q-, C-, and G-banding patterns in the germ-line and somatic chromosomes of Miastor sp. (Diptera: cecidomyidae)

Q-, C-, and G-banding patterns are described for the germ-line and somatic chromosomes of Miastor sp. The chromosome number in the germ line is 36, which is 3 less than that previously reported for the same cultured line 18 years ago. There are 8 chromosome groups: 8 large acrocentrics, 11 large and medium submetacentrics, 4 medium metacentrics, 4 medium subtelocentrics, 6 medium telocentrics, one medium acrocentric, one small submetacentric, and one small telocentric. All 8 large acrocentrics have a Q-band and an interstitial C-band in the short arm, suggesting that these chromosomes are at least partially homologous (or homeologous) and that the germ line originally was polyploid. Only one other germ-line chromosome, the small submetacentric, has a Q-band and an interstitial C-band. In somatic cells there are 8 chromosomes, 28 chromosomes having been eliminated during early cleavage. Three of the four pairs of somatic chromosomes are heteromorphic, despite the indications of a polyploid origin of the germ-line chromosomes and despite the presence of somatic pairing. Furthermore, there is a great deal of restriction on which chromosomes are retained in somatic cells, and it may be that the same 8 chromosomes are retained by all embryos. The G-banding pattern is not as clear as the other two banding patterns. The findings are discussed in relation to observations in other cecidomyids, and a model for the evolution of the chromosome system of Miastor is presented.     

红嘴鸥核型及C带和银带

本文以骨髓细胞常规空气干燥法和Sumner(1972)的方法(C带),Howell(1980)的方法(银带),对近年来昆明过冬的红嘴鸥的核型及其C带和银带进行了分析,结果显示出:红嘴鸥的2n应为68±。多数染色体的着丝粒区均显示出一个深浅不同的C带。Z染色体上有一个微小而模糊的C带,而W染色体大部分染色质被深染。其染色体经快速银染后表明,2对NORs均在微小染色体上。     

水貂的染色体研究

采用复制带、C带和硝酸银染色等分带技术研究了水貂的核型和带型。结果表明,2n=30,枝型为10（M）＋16（SM）＋2（A）,XX（M）。C-带显示该水貂的一些染色体的结构异染色质比较丰富,从着丝粒区域延伸到两臂上,No.5染色体着丝粒结构异染色质有些弱化;X染色体的结构异染色质较常染色体的丰富。Ag-NORs有3个,分布在No.8染色体的次缢痕区域和一条No.2染色体长臂接近着丝粒的区域。     

Heteromorphic Z and W sex chromosomes in Physalaemus ephippifer (Steindachner, 1864) (Anura, Leiuperidae)

Heteromorphisms between sex chromosomes are rarely found in anurans and sex chromosome differentiation is considered to be a set of recent recurrent events in the evolutionary history of this group. This paper describes for the first time heteromorphic sex chromosomes Z and W in the leiuperid genus Physalaemus. They were found in P. ephippifer, a species of the P. cuvieri group, and corresponded to the eighth pair of its karyotype. The W chromosome differed from the Z chromosome by the presence of an additional segment in the short arm, composed of a distal NOR and an adjacent terminal DAPI-positive C-band. The identification of this sex chromosome pair may help in future investigations into the sex determining genes in the genus Physalaemus.     

Analysis of the monomeric alphoid sequences in the pericentromeric region of human chromosome 7

To further define the structure of the pericentromeric region of human chromosome 7, we have identified and characterized a YAC clone (YAC 311.H5) containing the D7S1480 locus, which maps to the short arm near the centromere of this chromosome, by linkage in CEPH families and radiation hybrid analysis. This YAC contains two new blocks of alphoid DNA (named Z5 and Z6). Both Z5 and Z6 show monomeric structures and a lack of higher-order repeats, and, therefore, belong to suprachromosomal family type 4 (M1). The orientation of the two blocks and the physical distances over the region were defined by pulsed-field gel electrophoresis (PFGE) and fluorescence in situ hybridization on chromatin fibers (FiberFISH). A YAC contig spanning the centromeric region has been developed by STS content.     

Karyotypes of three somaclonal variants and wild plants ofAllium tuberosum by bicolor FISH

Using the fluorescence in situ hybridization (FISH) technique, we conducted karyotype analyses to identify the lost chromosomes in three somaclonal variants obtained from tissue culture of wildAllium tuberosum (2n = 4X = 32). The three lost chromosomes of the At29 variant (2n = 29) were all chromosome 2, the two for At30 (2n = 30) were chromosomes 7 and 8, and At31 was missing chromosome 2. Chromosome compositions of these variants were confirmed as being fixed lines during two years of greenhouse cultivation. The bicolor FISH technique, involving both 5S and 18S–5.8S–26S ribosomal RNA genes as probes, was used to assign chromosomal locations and to confirm whether the lost chromosomes contained any rRNA markers. The 5S rRNA gene signals in all variants as well as the wild type were detected as two sets, one on the intercalary region of the short arm of chromosome 3, the other on the intercalary region of the long arm of chromosome 6. One 18S–5.8S–26S rRNA gene site on the secondary constriction included a flanking satellite and terminal region on the short arm of chromosome 8. Signals of the 18S–5.8S–26S rRNA gene in At30 showpd in only three chromosomes, indicating that one of the lost chromosomes was chromosome 8. Overall, three marker chromosomes were established by FISH, using rRNA multigene families.     

The importance of further cytogenetic and molecular investigation of acrocentric variants: justification by presentation of a case [t(8;14)(q24;p11)]

Summary On routine chromosome analysis a moderately retarded 18-year old man was found to have an unusual short arm on one chromosome 14. With GTL-banding this chromosome showed an enlarged short arm with no evident secondary constriction. Negative CBG-banding of the short arm suggested the possibility of a translocation involving euchromatin. Interpretation of the abnormality as an unbalanced translocation relied on chromosome analysis using GTL-, CBG-, and Ag-NOR-banding of the proband's phenotypically normal mother, who was found to be carrying a balanced translocation involving chromosomes 8 and 14. In situ hybridization of sequences known to map to the short arm of chromosome 14 confirmed the interpretation and established that the breakpoint was within p11. The patient, whose karyotype is 46,XY,-14,+der(14)t(8;14)(q24.1;p11), is trisomic for the terminal end of the long arm of chromosome 8. The patient's clinical features are described and compared with those reported in patients trisomie for this region. This study demonstrates the importance of using a number of different banding techniques in conjunction with in situ hybridization for the investigation of morphologically unusual acrocentric short arm variants seen at routine diagnosis.     

The origin of the genetical diversity of Microtus mandarinus chromosomes

Here we describe our comparative studies on two types of X chromosomes, namely X(M) and X(SM,) of the mandarin vole (Microtus mandarinus). By chromosome G- and C-banding analysis, we have found that two different types of X chromosomes exist in mandarin voles. The two types of X chromosomes present two different G- and C-banding patterns: the X(M) chromosome is a longer metacentric X chromosome which is C-band negative; and the X(SM) is a shorter submetacentric X chromosome which has one C-band at the centromere and another one at the middle part of the short arm. The X(SM) has 6 G-bands including one on the kinetochore, one in the middle of the short arm, and four on the long arm. The X(M) has 7 G-bands including one on the kinetochore, two on the short arm, and four on the long arm. We have further found that female voles can be grouped into three types based on the composition of the X chromosome but the male voles have only one type. The three female groups are: (1) female voles (X(M)X(SM)), in which the two X chromosomes are different, the longer one is metacentric and the shorter is submetacentric; (2) female vole (X(SM)X(SM)), in which the two X chromosomes are both submetacentric; (3) female vole (X(M)O), in which there is only one X chromosome that is metacentric. Surprisingly, we have never found female voles with X(M)X(M), females with X(SM)O or males with X(M)Y. We hypothesize that the X(SM) chromosome is derived from the X(M) through its breakage and re-joining. The paper also discusses the formation of X(M)O females.     

Short rib-polydactyly syndrome,Majewski type,in two male siblings

Summary C-band polymorphisms of chromosomes 1, 9, and 16 were investigated in (1) 165 newborn infants, (2) 93 Down's syndrome patients, (3) 69 patients with acquired mental retardation, (4) 54 idiopathic patients, and (5) 48 idiopathics with multiple congenital malformations. The C-band size of chromosomes 1 and 9 showed a similar nonnormal distribution in all five groups. A significantly higher frequency of C bands, some of which were located on the short arm of chromosome 9, was observed in the groups of patients with Down's syndrome and with idiopathic mental retardation.     

Structural organization of the heterochromatic region of human chromosome 9

Giemsa-11, G-banding and Lateral Asymmetry staining techniques were used to define the substructure of the C-band heterochromatin of human chromosome 9, in a sample of 108 different chromosomes 9, from 54 individuals. In this sample, the juxtacentromeric portion of the C-band region stained positive by the G-banding technique while Giemsa-11 delineated a more distally located block. Examination of the pericentric inversions generally revealed that the entire C-band region is changed with the substructural organization left intact; i.e. the G-band is proximal, the G-11 distal to the centromere. The partial pericentric inversions were found to have larger than average amounts of G-band heterochromatin on the short arm. The G-11 staining was in its usual position on the long arm with none on the short arm. Such apparent inversions therefore may not represent true inversions. — Long heterochromatic regions frequently had a segmented appearance when stained with G-11; there was a dark G-band within the pale heterochromatic region when stained with the G-banding technique which corresponded in location to the achromatic gap produced by G-11. This extra G-band may have been derived from the juxtacentromeric G-band by processes analogous to unequal crossing over. — Simple lateral asymmetry was consistently present only in the G-band heterochromatin of those chromosomes 9 containing large blocks of G-band positive material. Examination of the portion of the C-band which would correspond to the G-11 positive material revealed no consistent patterns of asymmetry. Usually both strands were heavily stained and symmetrical but occasionally there were light areas present on one strand suggestive of compound lateral asymmetry.     

Identification of 28 DNA fragments that detect RFLPs in 13 distinct physical regions of the short arm of chromosome 5.

A series of 175 lambda phage carrying human inserts isolated from a library that is specific for the short arm of human chromosome 5 (5p) have been regionally mapped on 5p using a deletion mapping panel of 16 human-hamster cell hybrids, each of which contains a chromosome 5 with a different deletion in the short arm. Seventy-five single copy DNA fragments were screened with 12 restriction enzymes for their ability to detect restriction fragment length polymorphisms (RFLPs). Twenty-eight of these DNA fragments, which are located in 13 distinct physical regions of 5p, were found to detect RFLPs. These DNA markers make it possible to construct a linkage map that will span the entire length of 5p and will allow the relationship between genetic and physical distance for this region of the genome to be examined at a high level of resolution.     

福建大头蛙的核型及带型分析

利用骨髓细胞蒸气固定法制备染色体标本,研究了福建大头蛙(Limnonectesfujianensis)黄山居群的核型、C 带和Ag NORs。结果表明,福建大头蛙核型为2n =2 2 =2 0M 2SM ,NF =44,次缢痕位于No 1 0q ;各染色体均有着丝粒C 带,3p、9q出现插入型C 带;Ag NORs位于1 0q。