Absence of satellite III DNA in the centromere and the proximal long-arm region of human chromosome 14: analysis of a 14p- variant.

Cytogenetic methods and molecular probes derived from the centromere and short arm of chromosome 14 were used to investigate the structural properties of a chromosome 14 variant. Results of GTL, CBG, Ag-NOR, and non-banded Giemsa staining of the chromosomes suggested the complete absence of the short arm and possibly a large part of the centromere. Negative in situ hybridisation with an alpha satellite III probe confirmed the absence of the arm; the detection of normal amounts of alpha satellite DNA, however, indicated retention of the centromeric domain. The natural occurrence of a human acrocentric variant lacking a short arm was thus established. Within the detection limits of the methods used, the results demonstrate that satellite III DNA is not essential for normal centromeric activity and allow us to exclude the presence of this satellite DNA within the centromere and proximal long-arm region of human chromosome 14.     

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.     

NOR and nucleolus in the spermatogenesis of acridoid grasshoppers

By means of silver staining procedures of light microscopy the characteristics of the nucleolus and the NORs have been investigated in meiocytes of different grasshopper species. Our results show that: (1) Two is the most common number of chromosomes per haploid genome carrying active NORs although this number may vary from one up to five; (2) NOR activity is preferentially located on medium and short chromosomes but the X and the megameric chromosome are involved in nucleolar organization in a high proportion of the species studied; (3) The NOR location is normally restricted to one end in acro-telocentrics and to the short arm, near the centromere region, in metacentrics; (4) A marked correlation is observed between the number of nucleoli present in the spermatogonial cells and in the first meiotic prophase of a given species; (5) In some cases, the nucleoli are associated to chromosomes during spermatogonial premetaphases.     

Centromere function and nondisjunction are independent components of the maize B chromosome accumulation mechanism

Supernumerary or B chromosomes are selfish entities that maintain themselves in populations by accumulation mechanisms. The accumulation mechanism of the B chromosome of maize (Zea mays) involves nondisjunction at the second pollen mitosis, placing two copies of the B chromosome into one of the two sperm. The B chromosome long arm must be present in the same nucleus for the centromere to undergo nondisjunction. A centromere, containing all of the normal DNA elements, translocated from the B chromosome to the short arm of chromosome 9 was recently found to be epigenetically silenced for centromeric function. When intact B chromosomes were added to this genotype, thus supplying the long arm, the inactive centromere regained the property of nondisjunction causing the translocation chromosome 9 to be differentially distributed to the two sperm or resulted in chromosome breaks in 9S, occasionally producing new translocations. Translocation of the inactive B centromere to chromosome 7 transferred the nondisjunction property to this chromosome. The results provide insight into the molecular and evolutionary basis of this B chromosome accumulation mechanism by demonstrating that nondisjunction is caused by a process that does not depend on normal centromere function but that the region of the chromosome required for nondisjunction resides in the centromeric region.     

High-resolution pachytene chromosome mapping of bacterial artificial chromosomes anchored by genetic markers reveals the centromere location and the distribution of genetic recombination along chromosome 10 of rice

Large-scale physical mapping has been a major challenge for plant geneticists due to the lack of techniques that are widely affordable and can be applied to different species. Here we present a physical map of rice chromosome 10 developed by fluorescence in situ hybridization (FISH) mapping of bacterial artificial chromosome (BAC) clones on meiotic pachytene chromosomes. This physical map is fully integrated with a genetic linkage map of rice chromosome 10 because each BAC clone is anchored by a genetically mapped restriction fragment length polymorphism marker. The pachytene chromosome-based FISH mapping shows a superior resolving power compared to the somatic metaphase chromosome-based methods. The telomere-centromere orientation of DNA clones separated by 40 kb can be resolved on early pachytene chromosomes. Genetic recombination is generally evenly distributed along rice chromosome 10. However, the highly heterochromatic short arm shows a lower recombination frequency than the largely euchromatic long arm. Suppression of recombination was found in the centromeric region, but the affected region is far smaller than those reported in wheat and barley. Our FISH mapping effort also revealed the precise genetic position of the centromere on chromosome 10.     

Differences in AT- and GC-base pair ratios in DNA of the paracentromeric heterochromatin of chromosome 1 in two human cell types. I. Autoradiographic analysis of the incorporation of 3H-labeled thymidine and 3H-labeled deoxycytidine.

The distribution of AT- and GC-base pairs in DNA along chromosomes 1 and 2 has been studied in primary cultures of human embryo fibroblasts and peripheral blood leukocytes by an autoradiographic method using 3H-labeled thymidine and 3H-labeled deoxycytidine. The two cell types differed in their relative contents of DNA and in the ratio of AT and GC pairs at the centromere and the adjacent region of heterochromatin in chromosome 1. The DNA content of this section was higher in fibroblasts than in leukocytes, mainly because of AT pairs. In both cell types, the telomere in the short arm of this chromosome had a higher content of GC pairs than AT pairs. No differences were observed in base pair distribution along chromosome 2 in the two types. This phenomenon may be due to incomplete replication, or to loss by some means of part of the genetic material during the development and differentiation of the cellular systems.     

Characteristics of the distribution of DNA repetitive sequences in the sex chromosomes of 4 species of rodent

Four rodent species with very large heterochromatic regions on the sex chromosomes have been studied using in situ DNA/DNA hybridization techniques. Repetitious DNA fractions were obtained at C0t 0-0.01. Heterochromatic regions of X and X chromosomes of Cricetulus barabensis and Phodopus sungorus, and the heterochromatic long arm of the Y chromosome of Mesocricetus auratus do not contain disproportionately high amounts of repeated DNA sequences. Heterochromatic regions on sex chromosomes of Microtus subarvalis contain high amounts of repeated DNA sequences. Additional heterochromatic autosomal arms, a heterochromatic arm of the X chromosome, and a short arm of the Y chromosome of Mesocricetus auratus contain high amounts of repeated DNA sequences too.     

Physical mapping of three fruit ripening genes：Endopolygalacturonase,ACC oxidase and ACC synthase from apple（Malus x domestica） in an apple rootstock A106（Malus sieboldii

The apple rootstock,A106(Malus sieboldii),had 17 bivalents in pollen mother cells at meiotic metaphase 1,and 17 chromosomes in a haploid pollen cell.Karyotypes were prepared from root-tip cells with 2n=34 chromosomes,Seven out of 82 karyotypes(8.5%) showed one pari of satellites at the end of the short arm of chromosome 3.C-bands were shown on 6 pairs of chromosomes 2,4,6,8,14,and 16 near the telomeric regions of short arms.Probes for three ripening-related genes from Malus x domestica:endopolygalacturonase(EPG,0.6kb),ACC oxidase(1.2kb),and ACC synthase(2kb)were hybridized in situ to metaphase chromosomes of A106.Hybridization sites for the EPG gene were observed on the long arm of chromosome 14 in 15 out of 16 replicate spreads and proximal to the centromere of chromosomes 6 and 11.For the ACC oxidase gene,hylridization sites were observed in the telomeric region of the short arm of chromosomes 5 and 11 in 87% and 81% of 16 spreads respectively,proxiaml to the centromere of chromosome 1 in 81% of the spreads,and on the long arm of chromosome 13 in 50% of the spreads. Physical mapping of three fruit ripening genes in an apple rootstock A106.Twenty five spreads were studied for the ACC synthase gene and hybridization sites were observed in the telomeric region of the short arm of chromosome 12 in 96% of the spreads.chromosomes 9 and 10 in 76% of the spreads,and chromosome 17 in 56% of the spreads.     

Replication pattern of the X and Y chromosomes in partially synchronized human lymphocyte cultures

The replication pattern of the X and Y chromosomes at the beginning of the synthetic phase was studied in human lymphocyte cultures partially synchronized by the addition of 5-fluoro-2-deoxyuridine (FUdR). The data were evaluated statistically by an analysis of the distribution of silver grain counts over the X and Y chromosomes. —In cells from normal females, one of the X chromosomes began replication later than any other chromosomes of the complement. The short arm of the late replicating X chromosome started replication earlier than the long arm. The telomeric region of the short arm was a preferential site of DNA synthesis at the beginning of replication. —In partially synchronized lymphocyte cultures from a patient with the XXY syndrome, the Y chromosome started replication together with the late replicating X chromosome. The Y chromosome most frequently replicated synchronously with the short arm of the X. The centromeric region of the Y chromosome initiated synthesis before the telomeric region and appeared to replicate synchronously with the telomeric region of the short arm of the X. These findings are discussed with reference to the pairing of the X and Y chromosomes at meiosis.Supported in part by the National Institute of Health Research Grant HD-01979 and National Foundation Birth Defects Research Grant CRCS-40. Dr. Knight was a predoctoral fellow under National Institute of Health Training Program HD-00049-09.     

Evidence for Emergence of Sex-Determining Gene(s) in a Centromeric Region in Vasconcellea parviflora

Sex chromosomes have been studied in many plant and animal species. However, few species are suitable as models to study the evolutionary histories of sex chromosomes. We previously demonstrated that papaya (Carica papaya) (2n = 2x = 18), a fruit tree in the family Caricaceae, contains recently emerged but cytologically heteromorphic X/Y chromosomes. We have been intrigued by the possible presence and evolution of sex chromosomes in other dioecious Caricaceae species. We selected a set of 22 bacterial artificial chromosome (BAC) clones that are distributed along the papaya X/Y chromosomes. These BACs were mapped to the meiotic pachytene chromosomes of Vasconcellea parviflora (2n = 2x = 18), a species that diverged from papaya ∼27 million years ago. We demonstrate that V. parviflora contains a pair of heteromorphic X/Y chromosomes that are homologous to the papaya X/Y chromosomes. The comparative mapping results revealed that the male-specific regions of the Y chromosomes (MSYs) probably initiated near the centromere of the Y chromosomes in both species. The two MSYs, however, shared only a small chromosomal domain near the centromere in otherwise rearranged chromosomes. The V. parviflora MSY expanded toward the short arm of the chromosome, whereas the papaya MSY expanded in the opposite direction. Most BACs mapped to papaya MSY were not located in V. parviflora MSY, revealing different DNA compositions in the two MSYs. These results suggest that mutation of gene(s) in the centromeric region may have triggered sex chromosome evolution in these plant species.     

Localization of DNA sequences in region Xp21 of the human X chromosome: Search for molecular markers close to the duchenne muscular dystrophy locus

Panels of somatic cell hybrid lines carrying various structural rearrangements of the human X chromosome short arm were analyzed with 21 X-chromosome-specific cloned DNA fragments. We mapped these molecular markers to five different regions of the short arm of the X chromosome. The results were confirmed by gene-dosage studies of human lymphoblasts with structurally abnormal X chromosomes. The ornithine transcarbamylase gene and four anonymous DNA sequences map within band Xp21, flanking the presumed locus for Duchenne muscular dystrophy.     

Chromosomal localization of several families of repetitive sequences by in situ hybridization.

Four recombinant DNA clones (H1, H7, H12, and H15) carrying low-repetitive human DNA were previously isolated from a human genomic library based on their specificity for chromosome 21 and were studied for their distribution as determined by in situ hybridization. Clone H7 hybridized to the satellite regions of chromosomes 13, 14, 15, 21, and 22 as well as to the centromere region of chromosome 1. Clone H12 hybridized strongly to chromosomes 11 and 17 and the centromere of the X. Clones H1 and H15 had a very widespread distribution throughout the genome. Clone H15 hybridized significantly more to the short arm of chromosome 18 than to any other chromosomal segment. Clone H1 hybridized strongly to the centromere of chromosome 19 and also showed random distribution on all the other human chromosomes. We conclude that these probes appear to represent four repetitive families that demonstrate in situ hybridization patterns that do not correspond with those of any other repetitive family. Further, the in situ hybridization patterns do not show the strong chromosome 21 specificity originally defined by Southern blot analysis. The nature and chromosomal localization of these repetitive families should be useful in regional mapping and evolutionary studies and give additional insight into chromosomal organization.     

Identification of a homeologous chromosome pair by in situ DNA hybridization to ribosomal RNA loci in meiotic chromosomes of cotton (Gossypium hirsutum).

In situ DNA hybridization with 18S-28S and 5S ribosomal DNA probes was used to map 18S-28S nucleolar organizers and tandem 5S repeats to meiotic chromosomes of cotton (Gossypium hirsutum L.). Mapping was performed by correlating hybridization sites to particular positions in translocation quadrivalents. Arm assignment required translocation quadrivalents with at least one interstitial chiasma and sufficient distance between the hybridization site and the centromere. We had previously localized a major 18S-28S site to the short arm of chromosome 9; here we mapped two additional major 18S-28S sites to the short arm of chromosome 16 and the left arm of chromosome 23. We also identified and mapped a minor 18S-28S site to the short arm of chromosome 7. Two 5S sites of unequal size were identified, the larger one near the centromere of chromosome 9 and the smaller one near the centromere of chromosome 23. Synteny of 5S and 18S-28S sites indicated homeology of chromosomes 9 and 23, while positions of the other two 18S-28S sites supplement genetic evidence that chromosomes 7 and 16 are homeologous.     

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。     

MAMMALIAN CHROMOSOMES IN VITRO : XVIII. DNA Replication Sequence in the Chinese Hamster

The complete DNA replication sequence of the entire complement of chromosomes in the Chinese hamster may be studied by using the method of continuous H³-thymidine labeling and the method of 5-fluorodeoxyuridine block with H³-thymidine pulse labeling as relief. Many chromosomes start DNA synthesis simultaneously at multiple sites, but the sex chromosomes (the Y and the long arm of the X) begin DNA replication approximately 4.5 hours later and are the last members of the complement to finish replication. Generally, chromosomes or segments of chromosomes that begin replication early complete it early, and those which begin late, complete it late. Many chromosomes bear characteristically late replicating regions. During the last hour of the S phase, the entire Y, the long arm of the X, and chromosomes 10 and 11 are heavily labeled. The short arm of chromosome 1, long arm of chromosome 2, distal portion of chromosome 6, and short arms of chromosomes 7, 8, and 9 are moderately labeled. The long arm of chromosome 1 and the short arm of chromosome 2 also have late replicating zones or bands. The centromeres of chromosomes 4 and 5, and occasionally a band on the short arm of the X are lightly labeled.     

A study of cryptic terminal chromosome rearrangements in recurrent miscarriage couples detects unsuspected acrocentric pericentromeric abnormalities

Fifty chromosomally normal couples with three or more miscarriages were examined using fluorescent in situ hybridisation (FISH) and a library of subtelomere-specific probes together with alphoid repeats mapping to the acrocentric centromeres. Six abnormalities were found. Firstly, a cryptic reciprocal subtelomere translocation between the long arm of a chromosome 3 and the short arm of a chromosome 10. The other five cryptic abnormalities involved the acrocentric chromosome pericentromeric regions and in one case also Yp. Two patients had a rearranged chromosome 13, where the centromeric region was found to be derived from the short arm, centromere and proximal long arm of chromosome 15. Another two patients had a derived chromosome 22, where the centromere was replaced by two other centromeres, one derived from chromosome 14 and the other from either chromosome 13 or 21, while one patient had the subtelomere region of Yp translocated onto the short arm of a chromosome 21. These abnormalities may be the underlying cause of the recurrent miscarriages, because they may result in abnormal pairing configurations at meiosis leading to non-disjunction of whole chromosomes at metaphase I. The frequency of rearrangements seen in the recurrent miscarriage patient population was significantly different from that in the control group ( P=0.0096, Fisher's exact test) due to the acrocentric pericentromeric abnormalities.     

Molecular mapping of the centromeres of tomato chromosomes 7 and 9

The centromeres of two tomato chromosomes have been precisely localized on the molecular linkage map through dosage analysis of trisomic stocks. To map the centromeres of chromosomes 7 and 9, complementary telo-, secondary, and tertiary trisomic stocks were used to assign DNA markers to their respective chromosome arms and thus to localize the centromere at the junction of the short and long arms. It was found that both centromeres are situated within a cluster of cosegregating markers. In an attempt to order the markers within the centric clusters, genetic maps of the centromeric regions of chromosomes 7 and 9 were constructed from F₂ populations of 1620Lycopersicon esculentum × L. pennellii (E × P) plants and 1640L. esculentum × L. pimpinellifolium (E × PM) plants. Despite the large number of plants analyzed, very few recombination events were detected in the centric regions, indicating a significant suppression of recombination at this region of the chromosome. The fact that recombination suppression is equally strong in crosses between closely related (E × PM) and remotely related (E × P) parents suggests that centromeric suppression is not due to DNA sequence mismatches but to some other mechanism. The greatest number of centromeric markers was resolved in theL. esculentum × L. pennellii F₂ population. The centromere of chromosome 7 is surrounded by eight cosegregating markers: three on the short arm, five on the long arm. Similarly, the centric region of chromosome 9 contains ten cosegregating markers including one short arm marker and nine long arm markers. The localization of centromeres to precise intervals on the molecular linkage map represents the first step towards the characterization and ultimate isolation of tomato centromeres.     

Y;autosome translocations and mosaicism in the aetiology of 45,X maleness: assignment of fertility factor to distal Yq11

Summary Three 45,X males have been studied with Y-DNA probes by Southern blotting and in situ hybridization. Southern blotting studies with a panel of mapped Y-DNA probes showed that in all three individuals contiguous portions of the Y chromosome including all of the short arm, the centromere, and part of the euchromatic portion of the long arm were present. The breakpoint was different in each case. The individual with the largest portion (intervals 1–6) is a fertile male belonging to a family in which the translocation is inherited in four generations. The second adult patient, who has intervals 1–5, is an azoospermic, sterile male. These phenotypic findings suggest the existence of a gene involved in spermatogenesis in interval 6 in distal Yq11. The third case, a boy with penoscrotal hypospadias, has intervals 1–4B. In situ hybridization with the pseudoautosomal probe pDP230 and the Y chromosome specific probe pDP105 showed that Y-derived DNA was translocated onto the short arm of a chromosome 15, 14, and 14, respectively. One of the patients was a mosaic for the 14p+ translocation chromosome. Our data and those reported by others suggest the following conclusions based on molecular studies in eight 45,X males: The predominant aetiological factor is Y;autosome translocation observed in seven of the eight cases. As the remaining case was a low-grade mosaic involving a normal Y chromosome, the maleness in all cases was due to the effect of the testis determing factor, TDF. There is preferential involvement of the short arm of an acrocentric chromosome (five out of seven translocations) but other autosomal regions can also be involved. The reason why one of the derivative translocation chromosomes becomes lost may be that it has no centromere.     

鳙鱼染色体的DAPI核型分析

利用腹腔注射秋水仙素制备肾细胞染色体方法和DAPI（4＇,6＇-diamidino-2-phenylindole）荧光染色的方法,对鳙鱼（Aristichthys,nobills）的染色体组型和染色质的分布进行了研究。结果表明,其二倍体数目为2n=48,核型为30M＋14SM＋2ST＋2T。DAPI荧光染色显示间期细胞核中荧光亮度较为一致,提示异染色质在间期细胞核中分布比较均一。而DAPI荧光染色在第1和第4染色体的短臂上较为明亮,其余染色体上的明亮区都分布在着丝粒区域,表明第1和第4染色体上的异染色质主要集中在染色体的短臂上,其余染色体的异染色质主要分布在着丝粒区域。     

Characterization of three de novo derivative chromosomes 16 by “Reverse chromosome painting” and molecular analysis

We have analyzed three de novo chromosome 16 rearrangements—two with a 16p+ chromosome and one a 16q+—none of which could be fully characterized by conventional cytogenetics. In each case, flow karyotypes have been produced, and the aberrant chromosome has been isolated by flow sorting. The origin of the additional material has been ascertained by amplifying and labeling the DNA of the abnormal chromosome by degenerate-oligonucleotide-primer–PCR and hybridizing it in situ to normal metaphase spreads (reverse chromosome painting). Both 16p+ chromosomes contain more than 30 Mb of DNA from the short arm of chromosome 9 (9p21.2-pter), while the 16q+ contains approximately 9 Mb of DNA from 2q37. The breakpoints on chromosome 16 have been localized in each case; the two breakpoints on the short arm are at different points within the terminal band, 16p13.3. The breakpoint on the long arm of chromosome 16 is very close to (within 230 kb of) the 16q telomere. Determination of the regions of monosomy and trisomy allowed the observed phenotypes to be compared with other reported cases involving aneuploidy for these regions.