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.     

Molecular hybridization of iodinated 4S, 5S, and 18S + 28S RNA to salamander chromosomes

4S, 5S, AND 18S + 28S RNA from the newt Taricha granulosa granulosa were iodinated in vitro with carrier-free 125I and hybridized to the denatured chromosomes of Taricha granulosa and Batrachoseps weighti. Iodinated 18S + 28S RNA hybridizes to the telomeric region on the shorter arm of chromosome 2 and close to the centromere on the shorter arm of chromosome 9 from T. granulosa. On this same salamander the label produced by the 5S RNA is located close to or on the centromere of chromosome 7 and the iodinated 4S RNA labels the distal end of the longer arm of chromosome 5. On the chromosomes of B. wrighti, 18S + 28S RNA hybridizes close to the centromeric region on the longer arm of the largest chromosome. Two centromeric sites are hybridized by the iodinated 5S RNA. After hybridization with iodinated 4S RNA, label is found near the end of the shorter arm of chromosome 3. It is concluded that both ribosomal and transfer RNA genes are clustered in the genome of these two salamanders.     

Physical mapping of the 5S ribosomal RNA genes in Arabidopsis thaliana by multi-color fluorescence in situ hybridization with cosmid clones

The 5S ribosomal RNA genes were mapped to mitotic chromosomes of Arabidopsis thaliana by fluorescence in situ hybridization (FISH). In the ecotype Landsberg erecta, hybridization signals appeared on three pairs of chromosomes, two of which were metacentric and the other acrocentric. Hybridization signals on one pair of metacentric chromosomes were much stronger than those on the acrocentric and the other pair of metacentric chromosomes, probably reflecting the number of copies of the genes on the chromosomes. Other ecotypes, Columbia and Wassilewskija, had similar chromosomal distribution of the genes, but the hybridization signals on one pair of metacentric chromosomes were very weak, and detectable only in chromosomes prepared from young flower buds. The chromosomes and arms carrying the 5S rDNA were identified by multi-color FISH with cosmid clones and a centromeric 180 bp repeat as co-probes. The metacentric chromosome 5 and its L arm carries the largest cluster of the genes, and the short arm of acrocentric chromosome 4 carries a small cluster in all three ecotypes. Chromosome 3 had another small cluster of 5S rRNA genes on its L arm. Chromosomes 1 and 2 had no 5S rDNA cluster, but they are morphologically distinguishable; chromosome 1 is metacentric and 2 acrocentric. Using the 5S rDNA as a probe, therefore, all chromosomes of A. thaliana could be identified by FISH. Chromosome 1 is large and metacentric; chromosome 2 is acrocentric carrying 18S-5.8S-25S rDNA clusters on its short arm; chromosome 3 is metacentric carrying a small cluster of 5S rDNA genes on its L arm; chromosome 4 is acrocentric carrying both 18S-5.8S-25S and 5S rDNAs on its short (L) arm; and chromosome 5 is metacentric carrying a large cluster of 5S rDNA on its L arm.     

The location of repeated DNA sequences in the chromosomes of Chironomus tentans

Polytene chromosomes of Chironomus tentans were hybridized in situ with in vivo labelled nuclear and chromosomal RNA. Nuclear RNA formed hybrids preferentially in five distinct regions considered to contain clustered, repeated DNA sequences. These are the two nucleolar organizer regions, Balbiani ring 1 and 2, and the 5 S RNA genes in region 2A of chromosome II, which together comprised almost 70% of the total number of grains over the complement. The remaining grains were diffusely distributed over the chromosomes. There was a significant difference in the distribution of grains when RNA from different chromosomes was used for hybridization. Chromosome I RNA hybridized preferentially with chromosome I, and chromosome II+III RNA preferentially with chromosome II+III. Some regions within the chromosomes hybridized significantly more chromosomal RNA than other regions. A considerable cross-hybridization of RNA from one particular type of chromosome with the other chromosomes was also found. It is concluded that repeated DNA sequences which hybridize with heterogeneous chromosomal RNA in C. tentans are widely dispersed in the genome. Some of these sequences have a delimited localization, others are dispersed, and some sequences which are transcribed in one particular chromosome are present also in the other chromosomes.     

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.     

Karyotype analysis of Lilium longiflorum and Lilium rubellum by chromosome banding and fluorescence in situ hybridisation.

Detailed karyotypes of Lilium longiflorum and L. rubellum were constructed on the basis of chromosome arm lengths, C-banding, AgNO3 staining, and PI-DAPI banding, together with fluorescence in situ hybridisation (FISH) with the 5S and 45S rDNA sequences as probes. The C-banding patterns that were obtained with the standard BSG technique revealed only few minor bands on heterologous positions of the L. longiflorum and L. rubellum chromosomes. FISH of the 5S and 45S rDNA probes on L. longiflorum metaphase complements showed overlapping signals at proximal positions of the short arms of chromosomes 4 and 7, a single 5S rDNA signal on the secondary constriction of chromosome 3, and one 45S rDNA signal adjacent to the 5S rDNA signal on the subdistal part of the long arm of chromosome 3. In L. rubellum, we observed co-localisation of the 5S and 45S rDNA sequences on the short arm of chromosomes 2 and 4 and on the long arms of chromosomes 2 and 3, and two adjacent bands on chromosome 12. Silver staining (Ag-NOR) of the nucleoli and NORs in L. longiflorum and L. rubellum yielded a highly variable number of signals in interphase nuclei and only a few faint silver deposits on the NORs of mitotic metaphase chromosomes. In preparations stained with PI and DAPI, we observed both red- and blue-fluorescing bands at different positions on the L. longiflorum and L. rubellum chromosomes. The red-fluorescing or so-called reverse PI-DAPI bands always coincided with rDNA sites, whereas the blue-fluorescing DAPI bands corresponded to C-bands. Based on these techniques, we could identify most of chromosomes of the L. longiflorum and L. rubellum karyotypes.     

水稻45S rDNA和5S rDNA的染色体定位研究

45SrDNA和5SrDNA是水稻中与核糖体RNA合成有关的2个功能片段,有关这2个序列在水稻染色体上的位置,不同研究者的研究结果不尽相同,在获得水稻染色体清晰制片的基础上,通过FISH确定了45SrDNA序列位于水稻的第9号和第10号染色体的短臂末端,并且第9号染色体上的拷贝数多于第10号染色体,5SrDNA序列位于第11号染色体短臂靠近着丝点处。     

Localization of 5S RNA and rRNA genes in the Norway rat

The genes coding for the two classes of ribosomal RNA molecules, 5S RNA and 18+28S RNA, have been localized in the Norway rat (Rattus norvegicus). The 18+28S RNA cistrons are found on three chromosomes, at secondary constrictions on the short arms of chromosomes 3 and 12 and at the telomere of the short arm of chromosome 11. These sites were confirmed using the silver staining technique for nucleolar organizer regions. Two sites were found for the 5S RNA genes; one is closely linked to the 18+28S gene site on chromosome 12. The second site is at or near the telomere of the long arm of chromosome 19.     

Spontaneous chromosomal rearrangements in cultivated and wild barleys

Summary Four of 1,240 cultivated barley lines collected from different regions of the world and 3 of 120 lines of wild barley, Hordeum spontaneum C. Koch, carry spontaneous reciprocal translocations. Break-point positions and rearrangements in the interchanged chromosomes have been examined by both test crosses and Giemsa banding techniques. The four translocation lines in cultivated barley were all of Ethiopian origin and have the same translocation involving chromosomes 2 and 4. The breakpoints are at the centromeres of both chromosomes, resulting in interchanged chromosomes 2S+4S and 2L+4L (S=short arm, L=long arm). A wild barley line, Spont.II, also has translocated chromosomes 2 and 4 which are broken at the centromeres. The resultant chromosomes are, however, 2S+4L and 2L+4S. Another wild barley line, Spont.S-4, has interchanged chromosomes with breakpoints in the short arm of chromosome 3 and the long arm of chromosome 7. In addition, this line has a paracentric inversion in the short arm of chromosome 7 that includes a part of nucleolar constriction, resulting in two tandemly arranged nucleolar constrictions. The third wild barley line, Spont.S-7, has interchanged chromosomes with breakpoints in the long arms of both chromosomes 3 and 6. The translocated chromosome 3 is metacentric and the translocated chromosome 6 has a long arm similar in length to the long arm of chromosome 7.     

Individual chromosome assignment and chromosomal collinearity in Gossypium thurberi, G. trilobum and D subgenome of G. barbadense revealed by BAC-FISH

The experiment on individual chromosome assignments and chromosomal diversity was conducted using a multi-probe fluorescence in situ hybridization (FISH) system in D subgenome of tetraploid Gossypium barbadense (D(b)), G. thurberi (D(1)) and G. trilobum (D(8)), which the later two were the possible subgenome donors of tetraploid cottons. The FISH probes contained a set of bacterial artificial chromosome (BAC) clones specific to 13 individual chromosomes from D subgenome of G. hirsutum (D(h)), a D genome centromere-specific BAC clone 150D24, 45S and 5S ribosomal DNA (rDNA) clones, respectively. All tested chromosome orientations were confirmed by the centromere-specific BAC probe. In D(1) and D(8), four 45S rDNA loci were found assigning at the end of the short arm of chromosomes 03, 07, 09 and 11, while one 5S rDNA locus was successfully marked at pericentromeric region of the short arm of chromosome 09. In D(b), three 45S rDNA loci and two 5S rDNA loci were found out. Among them, two 45S rDNA loci were located at the terminal of the short arm of chromosomes D(b)07 and D(b)09, whilst one 5S rDNA locus was found situating near centromeric region of the short arm of chromosome D(b)09. The positions of the BAC clones specific to the 13 individual chromosomes from D(h) were compared between D(1), D(8) and D(b). The result showed the existence of chromosomal collinearity within D(1) and D(8), and as well between them and D(b). The results will serve as a base for understanding chromosome structure of cotton and polyploidy evolution of cotton genome and will provide bio-information for assembling the sequences of finished and the on-going cotton whole genome sequencing projects.     

Homologous recombination and transposition generate chromosome I neopolymorphism during meiosis in Saccharomyces cerevisiae

We have studied the meiotic segregation of a chromosome length polymorphism (CLP) in the yeast Saccharomyces cerevisiae. The neopolymorphism frequently observed within the smallest chromosomes (I, VI, III and IX) is not completely understood. We focused on the analysis of the structure of chromosome I in 88 segregants from a cross between YNN295 and FL100trp. Strain FL100trp is known to carry a reciprocal translocation between the left arm of chromosome III and the right arm of chromosome I. PCR and Southern hybridization analyses were performed and a method for the rapid detection of chromosome I rearrangements was developed. Seven chromosome I types were identified among the 88 segregants. We detected 22 recombination events between homologous chromosomes I and seven ectopic recombination events between FL100trp chromosome III and YNN295 chromosome I. These recombination events occurred in 20 of the 22 tetrads studied (91%). Nine tetrads (41%) showed two recombination events. This showed that homologous recombination involving polymorphic homologues or heterologous chromosomes is the main source of neopolymorphism. Only one of the seven chromosome I variants resulted from a transposition event rather than a recombination event. We demonstrated that a Ty1 element had transposed within the translocated region of chromosome I, generating mutations in the 3′ LTR, at the border between U5 and PBS. Received: 7 May 1999 / Accepted: 14 February 2000     

Satellite DNA derived from 5S rDNA in Physalaemus cuvieri (Anura, Leiuperidae)

In the present study, we describe for the first time a family of 190-bp satellite DNA related to 5S rDNA in anurans and the existence of 2 forms of 5S rDNA, type I (201 bp) and type II (690 bp). The sequences were obtained from genomic DNA of Physalaemus cuvieri from Palmeiras, State of Bahia, Brazil. Analysis of the nucleotide sequence revealed that the satellite DNA obtained by digestion with EcoRI, called PcP190EcoRI, is 70% similar to the coding region of type I 5S rDNA and 66% similar to the coding region of type II 5S rDNA. Membrane hybridization and PCR amplification of the sequence showed that PcP190EcoRI is tandemly repeated. The satellite DNA as well as type I and type II 5S rDNA were localized in P. cuvieri chromosomes by fluorescent in situ hybridization. The PcP190EcoRI sequence was found in the centromeres of chromosomes 1-5 and in the pericentromeric region of chromosome 3. Type I 5S rDNA was detected in chromosome 3, coincident with the site of PcP190EcoRI. Type II 5S rDNA was located interstitially in the long arm of chromosome 5. None of these sequences co-localized with nucleolar organizer regions. Our data suggests that this satellite DNA originates from the 5S ribosomal multigene family, probably by gene duplication, nucleotide divergence and sequence dispersion in the genome.     

Heterochromatin and disproportionate chromosome replication in Anatopynia dyari (Diptera: Chironomidae)

Salivary gland chromosomes from four populations of Anatopynia dyari were examined together with mitotio and meiotic chromosomes from one of the sites. Both mitotic and meiotic cells possess large blocks of heterochromatin, some of which fluoresce brightly after quinacrine staining. Mitotic figures show twelve chromosomes consisting of a graded size series with 5 meta- and submetacentric pairs and one small telocentric pair. — Salivary gland chromosomes have a loose chromocentre and three distinct size classes of chromosomes. The size classes include 1 long metacentric, 4 medium acrocentrics and 1 very small telocentric which is also twice the thickness of the rest of the complement. Quinacrine staining produces bright fluorescence of the centromeric third of chromosome VI, some ectopically paired regions of the chromocentre, basal bands and the telomeres of some chromosomes. — The discrepancy between arm ratios and relative lengths of mitotic and polytene chromosomes is explained by under-replication of nonfluorescing heterochromatin in the latter case. Brightly fluorescing heterochromatin behaves in an anomalous manner suggesting that it is either over, or else not severely under-replicated in salivary glands. The extra thickness of chromosome VI also suggests that it undergoes an extra round of replication. — A common complex rearrangement was found in the long arm of chromosome III in three of the populations. In the one population tested it was in Hardy Weinberg equilibrium.     

Regulation of rRNA gene expression in a human familial 14p+ marker chromosome

Summary Chromosome studies were carried out on normal individuals from three generations of one family with a 14p+ chromosome. The short arm of the 14p+ chromosome stained well using Giemsa but poorly using quinacrine or trypsin-Giemsa methods; in each case there was an unstained secondary constriction near the distal end of the short arm. Two Ag bands of average size were present on the 14p+ short arm, indicating that there were two active nucleolus organizer regions; the Ag band near the distal end of the short arm was slightly larger than that near the centromere. Each of the two Ag bands was seen associated with the short arm of one or more of the other acrocentric chromosomes, with a combined frequency of association no greater than that of other chromosomes with an Ag band of the same size. In one individual, hybridization in situ with radioactive 18S and 28S ribosomal RNA showed six times as many autoradiographic silver grains over the short arm of the 14p+ chromosome as over that of any other acrocentric chromosome. The results obtained using in situ labeling indicated that the 14p+ chromosome had a large number of rRNA genes compared with the other acrocentric chromosomes, whereas the results obtained using Ag-staining and association frequency indicated that the 14p+ chromosome had no greater nucleolus organizer activity than did the other acrocentrics. The difference in these findings suggests that not all the rRNA genes on the 14p+ chromosome were active.     

Karyotype pecularities of human colorectal adenocarcinomas

Summary The data of the chromosome abnormalities in 15 colorectal tumors are presented. Rearrangements of the short arm of chromosome 17, leading to deletions of this arm or its part were noted in 12 tumors; in 2 other cases, one of the homologs of pair 17 was lost. The losses of at least one homolog of other chromosomal pairs were also found: chromosome 18, in 12 out of 13 cases with fully identified numerical abnormalities; chromosome 5, in 6 tumors; chromosome 21, in 5 cases; chromosomes 4, 15, and 22, in 4 cases each. Additional homologs of pair 20 were observed in 6 tumors, extra 8q was found in 5 tumors, and extra 13q in 6 cases. Rearrangements of the short arm of chromosome 1 and the long arm of chromosome 11 characterized 6 tumors each. The data recorded in our series differ from the data of other authors in two respects: the high incidence of the loss of sex chromosomes and the rearrangements of the long arm of chromosome 9. X chromosomes were missing in 4 out of 7 tumors in females, and Y chromosomes were absent in 5 out of 8 tumors in males. The long arm of chromosome 9 was rearranged in 8 cases, in 5 of them the breakpoint being at 9q22. Cytological manifestations of gene amplification (double minutes or multiple microchromosomes) were noted in 6 tumors.     

Contrasting rDNA evolution in lima bean (Phaseolus lunatus L.) and common bean (P. vulgaris L., Fabaceae)

Phaseolus vulgaris has two 5S rDNA sites in chromosomes 6 and 10 and from two up to nine 45S rDNA sites depending on the accession. The presence of three 45S rDNA sites, in chromosomes 6, 9 and 10, is considered the ancestral state for the species. For P. lunatus, only one 5S and one 45S rDNA sites in distinct chromosomes were known. In order to investigate the homeologies among these rDNA-bearing chromosomes and the stability of the rDNA sites in P. lunatus, rDNA and P. vulgaris chromosome-specific probes were hybridized in situ to P. lunatus. The chromosomes bearing the 5S and the 45S rDNA of P. lunatus are homeologous to chromosomes 10 and 6 of P. vulgaris, respectively. In contrast to the common bean, no variation in the number of rDNA loci was detected, except for a duplication of the 5S rDNA in the same chromosome in a small group of cultivars. These results suggest that the 5S rDNA site in chromosome 10 and the 45S rDNA site in chromosome 6 represent the ancestral loci in the genus. The 5S rDNA site in chromosome 10 of P. vulgaris is located in the long arm, while in P. lunatus it is present in the short arm, suggesting the occurrence of a transposition or a pericentric inversion after separation of both lineages.     

Physical characterization of the homoeologous group 5 chromosomes of wheat in terms of rice linkage blocks, and physical mapping of some important genes.

The wheat homoeologous Group 5 chromosomes were characterized physically in terms of rice linkage blocks using a deletion mapping approach. All three chromosomes, 5A, 5B, and 5D, were shown to have a similar structure, apart from the 4A-5A translocation on the distal end of chromosome arm 5AL. The physical mapping of rice markers on the deletion lines revealed that the whole of rice chromosome 9 is syntenous to a large block, proximal to the centromere, on the long arm. Likewise, a small segment of the distal end of the long arm showed conserved synteny with the distal one-third end of the long arm of rice chromosome 3. In between those conserved regions, there is a region on the long arm of the Group 5 chromosomes which shows broken synteny. The proximal part of the short arms of the Group 5 chromosomes showed conserved synteny with a segment of the short arm of rice chromosome 11 and the distal ends showed conserved synteny with a segment of rice chromosome 12. The physical locations of flowering time genes (Vrn and earliness per se) and the gene for grain hardness (Ha) on the Group 5 chromosomes were determined. These results indicate that comparative mapping using the deletion mapping approach is useful in the study of genome relationships, the physical location of genes, and can determine the appropriate gene cloning strategy.     

The mitotic chromosomes of Notophthalmus (=Triturus) viridescens: Localization of C banding regions and DNA sequences complementary to 18S, 28S and 5S ribosomal RNA

The metaphase chromosomes of Notophthalmus (Triturus) viridescens have been studied by C-banding and in situ hybridization. The chromosomes show the pericentric C-banding seen in many organisms and in addition have interstitial C-bands located a short distance from the pericentric C-bands on each chromosome arm. A few C-bands are seen in telomeric regions. Regions which hybridize in situ with 18S and 28S ribosomal RNA were found on three chromosome pairs. The animals studied fell into three groups with respect to which of the six possible sites showed detectable hybridization with 18S and 28S RNA. Individual animals differed not only in the pattern of in situ hybridization of ribosomal RNA but also in the number of ribosomal RNA cistrons in the genome as measured by saturation hybridization on purified DNA. In situ hybridization showed five pairs of chromosomes which contained DNA complementary to 5S RNA. The four pairs of subtelocentric chromosomes in the N. viridescens karyotype all have 5S DNA in the pericentric regions. The fifth cluster of 5S DNA is in the middle of one arm of the chromosomes in one of the two smallest submetacentric pairs in the genome. The five sites of 5S DNA differ markedly in the level of in situ hybridization with 5S cRNA.     

Identification and designation of telocentric chromosomes in barley by means of Giemsa N-banding technique

Summary Seven complete chromosomes and nine telocentric chromosomes in telotrisomics of barley (Hordeum vulgare L.) were identified and designated by an improved Giemsa N-banding technique. Karyotype analysis and Giemsa N-banding patterns of complete and telocentric chromosomes at somatic late prophase, prometaphase and metaphase have shown the following results: Chromosome 1 is a median chromosome with a long arm (Telo 1L) carrying a centromeric band, while short arm (Telo 1S) has a centromeric band and two intercalary bands. Chromosome 2 is the longest in the barley chromosome complement. Both arms show a centromeric band, an intercalary band and two faint dots on each chromatid at middle to distal regions. The banding pattern of Telo 2L (a centromeric and an intercalary band) and Telo 2S (a centromeric, two intercalary and a terminal band) corresponded to the banding pattern of the long and short arm of chromosome 2. Chromosome 3 is a submedian chromosome and its long arm is the second longest in the barley chromosome complement. Telo 3L has a centromeric (fainter than Telo 3S) and an intercalary band. It also shows a faint dot on each chromatid at distal region. Telo 3S shows a dark centromeric band only. Chromosome 4 is the most heavily banded one in barley chromosome complement. Both arms showed a dark centromeric band. Three dark intercalary bands and faint telomeric dot were observed in the long arm (4L), while two dark intercalary bands in the short arm (4S) were arranged very close to each other and appeared as a single large band in metaphase chromosomes. A faint dot was observed in each chromatid at the distal region in the 4S. Chromosome 5 is the smallest chromosome, which carries a centromeric band and an intercalary band on the long arm. Telo 5L, with a faint centromeric band and an intercalary band, is similar to the long arm. Chromosomes 6 and 7 are satellited chromosomes showing mainly centromeric bands. Telo 6S is identical to the short arm of chromosome 6 with a centromeric band. Telo 3L and Telo 4L were previously designated as Telo 3S and Telo 4S based on the genetic/linkage analysis. However, from the Giemsa banding pattern it is evident that these telocentric chromosomes are not correctly identified and the linkage map for chromosome 3 and 4 should be reversed. One out of ten triple 2S plants studied showed about 50% deficiency in the distal portion of the short arm. Telo 4L also showed a deletion of the distal euchromatic region of the long arm. This deletion (32%) may complicate genetic analysis, as genes located on the deficient segment would show a disomic ratio. It has been clearly demonstrated that the telocentric chromosomes of barley carry half of the centromere. Banding pattern polymorphism was attributed, at least partly, to the mitotic stages and differences in techniques.Contribution from the Department of Agronomy and published with the approval of the Director of the Colorado State University Experiment Station as Scientific Series Paper No. 2730. This research was supported in part by the USDA/SEA Competitive Research Grant 5901-0410-9-0334-0, USDA/ SEA-CSU Cooperative Research Grant 12-14-5001-265 and Colorado State University Hatch Project. This paper was presented partly at the Fourth International Barley Genetics Symposium, Edinburgh, Scotland, July 22–29, 1981     

人14p＋标记染色体的分子细胞遗传学研究

一例23岁女性患者因近五、六年来出现胡须、四肢多毛及偶有月经不规则而就诊。细胞遗传学检查发现一个短臂明显增大的亚中着丝粒的14号标记染色体14p ·p 区域GTG显带呈浅染,C-带暗染,都呈均匀的染色区。硝酸银染色在p 远侧端显现一个Ag-NOR,其大小与正常近端着丝粒染色体的无明显差异。应用~3H标记的7.3 kb长的rRNA基因探针进行染色体原位杂交,自显影银颗粒沿整个p 区域分布,p 上的银颗粒数是正常近端着丝粒染色体短臂上银颗粒平均数的5倍。这些结果排除了Y或其他染色体参加的重排形成p 的可能性,并表明Ag-NOR的大小或NOR的数目并不一定与rRNA基因的数量成正比。研究Dp 或Gp 类型的染色体变异,对了解人二倍体细胞内rRNA基因表达的调控有重要意义。