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.     

Physical mapping of unique nucleotide sequences on identified rice chromosomes

A physical mapping method for unique nucleotide sequences on specific chromosomal regions was developed combining objective chromosome identification and highly sensitive fluorescence in situ hybridisation (FISH). Four unique nucleotide sequences cloned from rice genomic DNAs, varying in size from 1.3 to 400 kb, were mapped on a rice chromosome map. A yeast artificial chromosome (YAC) clone with a 399 kb insert of rice genomic DNA was localised at the distal end of the long arm of rice chromosome (1q2.1) and a bacterial artificial chromosome (BAC) clone (180 kb) containing the rice leaf blast-resistant gene (Pi-b) was shown to occur at the distal end of the long arm of chromosome 2 (2q2.1). A cosmid (35 kb) with the resistance gene (Xa-21) against bacterial leaf blight was mapped on the interstitial region of the long arm on chromosome 11 (11q1.3). Furthermore a single RFLP marker, 1.29 kb in size, was mapped successfully to the distal region of the long arm of rice chromosome 4 (4q2.1). For precise localisation of the nucleotide sequences within the chromosome region, image analyses were effective. The BAC clone was localised to the specific region, 2q2.1:96.16, by image analysis. The result was compared with the known location of the BAC clone on the genetic map and the consistency was confirmed. The effectiveness and reliability in physically mapping nucleotide sequences on small plant chromosomes achieved by the FISH method using a variety of probes was unequivocally demonstrated.     

Allelotyping of human prostatic adenocarcinoma.

Allelotyping (using at least one probe detecting a restriction fragment length polymorphism on each chromosomal arm, with the exception of the short arms of the acrocentric chromosomes), showed loss of genetic information in 11 of 18 prostate adenocarcinoma specimens analyzed (61%). Frequent allelic deletions were detected on the long arm of chromosome 16 (6 of 10 informative cases, 60%), on the short arm of chromosome 8 (3 of 6 informative cases, 50%), and on the short and/or the long arms of chromosome 10 (6 of 11 informative cases (10p), 55% and 4 of 13 informative cases (10q), 30%, respectively). No losses of alleles were detected in any case unless at least one of the chromosomes 8, 10, or 16 also showed deletions. The long arm of chromosome 18 also showed a high frequency of allelic deletions (3 of 7 informative cases, 43%). Allelic deletions on the following chromosomes were detected at lower frequencies: chromosomes 2, 3, 7, 12, 13, 17, 22, and XY. Tumors with allelic deletions on more than one chromosome had a higher histological malignancy grade. Tumors from patients with advanced disease all showed allelic deletions.     

江苏櫓稻核型的初步分析

本文研究了江苏穭稻——一种草型栽培稻(Orysa sativa L.)的核型与染色体带型。结果表明,穭稻的核型有6对中位染色体(K_1,K_3,K_6,K,K(?)和K_(11)),4对亚中位染色体(K_2,K(?)K_0和K(?)),1对亚端位染色体(K_4)和1对随体染色体(K_(10)),在K_3染色体的长臂上有一次缢痕。Giemsa分带处理表明,穭稻染色体带型比较丰富,各条染色体的带型特征明显。本文还讨论了江苏穭稻与普通野生稻和栽培稻在核型及染色体带型上的异同。     

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.     

Deletion mapping of homoeologous group 6-specific wheat expressed sequence tags

To localize wheat (Triticum aestivum L.) ESTs on chromosomes, 882 homoeologous group 6-specific ESTs were identified by physically mapping 7965 singletons from 37 cDNA libraries on 146 chromosome, arm, and sub-arm aneuploid and deletion stocks. The 882 ESTs were physically mapped to 25 regions (bins) flanked by 23 deletion breakpoints. Of the 5154 restriction fragments detected by 882 ESTs, 2043 (loci) were localized to group 6 chromosomes and 806 were mapped on other chromosome groups. The number of loci mapped was greatest on chromosome 6B and least on 6D. The 264 ESTs that detected orthologous loci on all three homoeologs using one restriction enzyme were used to construct a consensus physical map. The physical distribution of ESTs was uneven on chromosomes with a tendency toward higher densities in the distal halves of chromosome arms. About 43% of the wheat group 6 ESTs identified rice homologs upon comparisons of genome sequences. Fifty-eight percent of these ESTs were present on rice chromosome 2 and the remaining were on other rice chromosomes. Even within the group 6 bins, rice chromosomal blocks identified by 1-6 wheat ESTs were homologous to up to 11 rice chromosomes. These rice-block contigs were used to resolve the order of wheat ESTs within each bin.     

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.     

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.     

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     

First survey of the wheat chromosome 5A composition through a next generation sequencing approach

Wheat is one of the world's most important crops and is characterized by a large polyploid genome. One way to reduce genome complexity is to isolate single chromosomes using flow cytometry. Low coverage DNA sequencing can provide a snapshot of individual chromosomes, allowing a fast characterization of their main features and comparison with other genomes. We used massively parallel 454 pyrosequencing to obtain a 2x coverage of wheat chromosome 5A. The resulting sequence assembly was used to identify TEs, genes and miRNAs, as well as to infer a virtual gene order based on the synteny with other grass genomes. Repetitive elements account for more than 75% of the genome. Gene content was estimated considering non-redundant reads showing at least one match to ESTs or proteins. The results indicate that the coding fraction represents 1.08% and 1.3% of the short and long arm respectively, projecting the number of genes of the whole chromosome to approximately 5,000. 195 candidate miRNA precursors belonging to 16 miRNA families were identified. The 5A genes were used to search for syntenic relationships between grass genomes. The short arm is closely related to Brachypodium chromosome 4, sorghum chromosome 8 and rice chromosome 12; the long arm to regions of Brachypodium chromosomes 4 and 1, sorghum chromosomes 1 and 2 and rice chromosomes 9 and 3. From these similarities it was possible to infer the virtual gene order of 392 (5AS) and 1,480 (5AL) genes of chromosome 5A, which was compared to, and found to be largely congruent with the available physical map of this chromosome.     

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.     

Cytogenetic Analysis of a Segment of the Y Chromosome of DROSOPHILA MELANOGASTER

Males carrying a large deficiency in the long arm of the Y chromosome known to delete the fertility gene kl-2 are sterile and exhibit a complex phenotype: (1) First metaphase chromosomes are irregular in outline and appear sticky; (2) spermatids contain micronuclei; (3) the nebenkerns of the spermatids are nonuniform in size; (4) a high molecular weight protein ordinarily present in sperm is absent; and (5) crystals appear in the nucleus and cytoplasm of spermatocytes and spermatids. In such males that carry Ste⁺ on their X chromosome the crystals appear long and needle shaped; in Ste males the needles are much shorter and assemble into star-shaped aggregates. The large deficiency may be subdivided into two shorter component deficiencies. The more distal is male sterile and lacks the high molecular weight polypeptide; the more proximal is responsible for the remainder of the phenotype. Ste males carrying the more proximal component deficiency are sterile, but Ste ⁺ males are fertile. Genetic studies of chromosome segregation in such males reveal that (1) both the sex chromosomes and the large autosomes undergo nondisjunction, (2) the fourth chromosomes disjoin regularly, (3) sex chromosome nondisjunction is more frequent in cells in which the second or third chromosomes nondisjoin than in cells in which autosomal disjunction is regular, (4) in doubly exceptional cells, the sex chromosomes tend to segregate to the opposite pole from the autosomes and (5) there is meiotic drive; i.e., reciprocal meiotic products are not recovered with equal frequencies, complements with fewer chromosomes being recovered more frequently than those with more chromosomes. The proximal component deficiency can itself be further subdivided into two smaller component deficiencies, both of which have nearly normal spermatogenic phenotypes as observed in the light microscope. Meiosis in Ste ⁺ males carrying either of these small Y deficiencies is normal; Ste males, however, exhibit low levels of sex chromosome nondisjunction with either deficient Y. The meiotic phenotype is apparently sensitive to the amount of Y chromosome missing and to the Ste constitution of the X chromosome.     

Chromosome bin map of expressed sequence tags in homoeologous group 1 of hexaploid wheat and homoeology with rice and Arabidopsis

A total of 944 expressed sequence tags (ESTs) generated 2212 EST loci mapped to homoeologous group 1 chromosomes in hexaploid wheat (Triticum aestivum L.). EST deletion maps and the consensus map of group 1 chromosomes were constructed to show EST distribution. EST loci were unevenly distributed among chromosomes 1A, 1B, and 1D with 660, 826, and 726, respectively. The number of EST loci was greater on the long arms than on the short arms for all three chromosomes. The distribution of ESTs along chromosome arms was nonrandom with EST clusters occurring in the distal regions of short arms and middle regions of long arms. Duplications of group 1 ESTs in other homoeologous groups occurred at a rate of 35.5%. Seventy-five percent of wheat chromosome 1 ESTs had significant matches with rice sequences (E < or = e(-10)), where large regions of conservation occurred between wheat consensus chromosome 1 and rice chromosome 5 and between the proximal portion of the long arm of wheat consensus chromosome 1 and rice chromosome 10. Only 9.5% of group 1 ESTs showed significant matches to Arabidopsis genome sequences. The results presented are useful for gene mapping and evolutionary and comparative genomics of grasses.     

Homoeologous pairing and recombination in <Emphasis Type="Italic">Solanum lycopersicoides</Emphasis> monosomic addition and substitution lines of tomato

We compared meiotic pairing and recombination between tomato ( Lycopersicon esculentum) and homoeologous Solanum lycopersicoides chromosomes in monosomic additions (MAs) and substitution lines (SLs), each representing a single chromosome of the nightshade in a tomato background. Three configurations of each alien chromosome and its two tomato homoeologues were detected by genomic in situ hybridization in MA-7, -8, and -10 at diakinesis/metaphase-I: 1 trivalent (III), 1 bivalent + 1 univalent (II+I), and 3 univalents (3I). The II+I category was by far the most common, and the univalent was from S. lycopersicoides 91-99.5% of the time, indicating a high degree of preferential (homologous) pairing. In the corresponding substitution lines, association of homoeologous chromosomes was much higher (up to 90% of the cells), presumably due to the absence of homologous partners. However, SL-10 showed a surprisingly high frequency of univalents (about 73%). Genome-wide analysis of chromosome pairing revealed a decrease in the average chiasma frequency for both monosomic additions and substitution lines. Recombination between tomato and the nightshade was restricted in all cases, the reduction being more severe in each monosomic addition than in the corresponding substitution line. Recombination rates in the substitutions were less than those observed for the same chromosomes in the first backcross generation. Chromosomes 8 and 10 showed the highest and the lowest rates of homoeologous recombination, respectively. No recombination was detected between markers on the long arm of chromosome 10, presumably due to the presence of a paracentric inversion differentiating the two genomes in this region. The frequency of homoeologous pairing at diakinesis/metaphase-I was significantly higher than the rate of homoeologous recombination detected in the progeny, suggesting a strong selection against recombinant products in meiotic or post-meiotic stages.     

程序性细胞死亡抑制基因Dad-1在水稻和玉米中的FISH定位(英文)

Dad-1是一种在动物和植物中都非常保守的细胞程序性死亡 (PCD) 抑制基因。作者利用 FISH (荧光原位杂交)首次把单拷贝水稻Dad-1基因物理定位在水稻第2号染色体短臂的端部(Fig.2 A,B&C)。我们还分析了它在玉米基因组中的同源序列。Southern 杂交结果显示在玉米基因组中确实存在水稻Dad-1 的同源序列(Fig.1)。FISH进一步展示了三个杂交信号分别在玉米4、5号染色体长臂和9号染色体短臂上(Fig.2 D,E&F),其信号距着丝粒的百分距离(FL值)分别为 91、98和96。其杂交位点的位置与水稻Dad-1所处的相对位置是相似的,它们都处于染色体臂的端部。这表明在一定的程度上,Dad-1基因不仅在序列同源性上而且在所处的染色体位置上具有保守性。 水稻Dad-1基因在水稻中的杂交信号检出率 (38%) 高于玉米中的。这表明与玉米相比,水稻Dad-1 基因的编码序列更容易与水稻染色体杂交;它与玉米中的相应序列可能只是部分同源。     

滇蜀豹子花核型及其变异研究

本文详细报道了滇蜀豹子花的核型,发现居群中存在两种细胞型,即A型和B型。A型参考核型为2n = 24＝2m(2SAT)+2sm+8st(4SAT)+12t(2SAT),其第3号两条同源染色体长臂均无居间随体：B型参考核型为2n=24＝2m(2SAT)+2sm+8st(2SAT)+12t(3SAT)+0—1b,其第3号一条同源染色体长臂紧靠着丝点处有一大而明显的居间随体,而另一条同源染色体则无,构成明显的3号染色体的结构杂合性。统计表明,居群中二者的比例近似为1A;2B。研究还发现了大量的体细胞染色体结构变异核型,表明滇蜀豹子花核型尚未趋于稳定,还处于强烈分化之中,高频率的体细胞染色体结构变异是其种内分化不可忽视的一种进化要素。     

Sperm chromosome analysis of a man heterozygous for a pericentric inversion of chromosome 3

Using a procedure in which human sperm were allowed to fertilize zona-free golden hamster (Mesocricetus auratus) eggs in vitro, the sperm chromosomes of a man heterozygous for inv(3) (p11q11) were analyzed. When the chromosomes were Q-banded, the inverted chromosome had the bright centromeric band on the short arm rather than on the long arm, as was seen in the normal No. 3. One hundred and eleven sperm chromosome spreads were examined, of which 64 contained the normal chromosome and 47 the inverted one. This was not significantly different from the expected 1:1 ratio. No sperm containing a chromosome imbalance caused by a crossover within the inversion were seen. Ten (8.1%) of the sperm contained chromosome abnormalities unrelated to the inversion. The ratio of X- to Y-bearing sperm was 55:45.     

Use of tyramide-fluorescence in situ hybridization and chromosome microdissection for ascertaining homology relationships and chromosome linkage group associations in oats

The physical mapping of single locus sequences by tyramide-fluorescence in situ hybridization (Tyr-FISH) and the analysis of sequences obtained from microdissected chromosomes were assayed as potential tools for (1) determining homology and homoeology among chromosome regions of Avena species, and (2) establishing associations between linkage groups and specific chromosomes. Low copy number probes, derived from resistance gene analogues (RGAs) and 2.8-4.5 kb long, successfully produced hybridization signals on specific chromosomes. Four sets of homoeologous chromosome regions were identified in the hexaploids using 3 probes that produced 4 single locus markers in A. strigosa and 2 in A. eriantha. Laser capture microdissection of metaphase I cells of A. sativa monosomic lines allowed the isolation of critical univalents. Sequences derived from 2 RGAs were successfully amplified in DNA extracted from univalents. In one instance, it was possible to map a nucleotide polymorphism specific for 1 chromosome. An association was established between this chromosome and its linkage groups in 2 hexaploid genetic maps. The results indicate that Tyr-FISH is useful in the characterization of homoeologous chromosome segments in hexaploids, whereas chromosome microdissection, as employed in this work, needs to be improved before it can routinely be used with meiotic chromosomes.     

Dissection of rye chromosome 1R in common wheat

Rye chromosome 1R contains many agronomically useful genes. Physical dissection of chromosome 1R into segments would be useful in mapping 1R-specific DNA markers and in assembling DNA clones into contig maps. We applied the gametocidal system to produce rearranged 1R chromosomes of Imperial rye (1R(i)) added to common wheat. We identified rearranged 1R(i) chromosomes and established 55 1R(i) dissection lines of common wheat carrying a single rearranged 1R(i) chromosome. Fifty-two of the rearranged 1R(i) chromosomes had single breakpoints and three had double breakpoints. The 58 breakpoints were distributed in the short arm excluding the satellite (12 breakpoints), in the satellite (4), in the long arm (28), and in the centromere (14). Out of the 55 lines, nine were homozygous for the rearranged 1R(i) chromosomes, and the remaining lines were hemizygous. We developed 26 PCR-based EST markers that were specific to the 1R(i) chromosome, and nine of them amplified 1R(i) arm-specific PCR products without restriction-enzyme digestion. Using the nine EST markers and two previously reported 1R-specific markers, we characterized the 55 1R(i) dissection lines, and also proved that we can select critical progeny plants carrying specific rearranged 1R(i) chromosomes by PCR, without cytological screening, in 48 out of the 55 hemizygous dissection lines.