酿酒酵母5号染色体精细物理图谱绘制

利用脉冲电泳（ＰｕｌｓｅｄＦｉｅｌｄＧｅｌＥｌｅｃｔｒｏｐｈｏｒｅｓｉｓ,ＰＦＧＥ）分析了酵母菌Ａ３６４ａ的电泳核型,以５号染色体专一探针确定了该染色体在电泳核型中的位置,以内切酶ＢａｍＨＩ对该染色体ＤＮＡ进行部分酶切后,与整合型载体ＹＩｐ５连接获得了一个染色体专一的基因文库,其转化子数目超过了理论要求值。从文库中筛选与已知探针有同源性的片段并用内切酶ＢａｍＨＩ,ＥｃｏＲＩ,ＨｉｎｄＩＩ,ＰｓｔＩ和ＳａｌＩ分析这些插入片段,获得了一个覆盖Ａ３６４ａ５号染色体（其长度估计为６２０ｋｂ）９．４％的精细物理图谱。利用边界克隆和菌落杂交将使我们能够对整条染色体进行进一步的“步查”     

Mapping Chromosome Rearrangement Breakpoints to the Physical Map of Caenorhabditis Elegans by Fluorescent in Situ Hybridization

A scheme for rapidly mapping chromosome rearrangements relative to the physical map of Caenorhabditis elegans is described that is based on hybridization patterns of cloned DNA on meiotic nuclei, as visualized by fluorescent in situ hybridization. From the nearly complete physical map, DNA clones, in yeast artificial chromosomes (YACs), spanning the rearrangement breakpoint were selected. The purified YAC DNAs were first amplified by degenerate oligonucleotide-primed polymerase chain reaction, then reamplified to incorporate fluorescein dUTP or rhodamine dUTP. The site of hybridization was visualized directly (without the use of antibodies) on meiotic bivalents. This allows chromosome rearrangements to be mapped readily if the duplicated, deficient or translocated regions do not pair with a normal homologous region, because the site or sites of hybridization of the probe on meiotic prophase nuclei will be spatially distinct. The pattern, or number, of hybridization signals from probes from within, or adjacent to, the rearranged region of the genome can be predicted from the genetic constitution of the strain. Characterization of the physical extent of the genetically mapped rearrangements places genetic landmarks on the physical map, and so provides linkage between the two types of map.     

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。     

Physical Mapping of Genetic Markers on the Short Arm of Chromosome 5

The deletion of the short arm of chromosome 5 is associated with the cri-du-chat syndrome. In addition, loss of this portion of a chromosome is a common cytogenetic marker in a number of malignancies. However, to date, no genes associated with these disorders have been identified. Physical maps are the first step in isolating causative genes, and genes involved in autosomal recessive disorders are now routinely mapped through the identification of linked markers. Extensive genetic maps based upon polymorphic short tandem repeats (STRs) have provided researchers with a large number of markers to which such disorders can be genetically mapped. However, the physical locations of many of these STRs have not been determined. Toward the goal of integrating the human genetic maps with the physical maps, a 5p somatic cell hybrid deletion mapping panel that was derived from patients with 5p deletions or translocations was used to physically map 47 STRs that have been used to construct genetic maps of 5p. These data will be useful in the localization of disease genes that map to 5p and may be involved in the etiology of the cri-du-chat syndrome.     

Genetic and Physical Mapping of the Dreher Locus on Mouse Chromosome 1

Mutations in the mouse dreher (dr) gene cause skeletal defects, hyperactivity, abnormal gait, deafness, white belly spotting, and hypoplasia of Müllerian duct derivatives. To map dr to high resolution, we utilized two crosses. Initially, we analyzed an intersubspecific intercross to construct a detailed genetic map of simple sequence length polymorphism markers within a 6.3-cM region surrounding the dr locus. Subsequently, we analyzed a second intersubspecific intercross segregating for the dr(6J) allele, which positioned dr within a 0.13-cM region between Rxrg and D1Mit370. A physical contig of BAC clones spanning the dr critical region was constructed, and eight potential dr candidate genes were excluded by genetic or physical mapping. Together these results lay the foundation for positional cloning of the dr gene.     

Fine Physical Mapping of Ph1, a Chromosome Pairing Regulator Gene in Polyploid Wheat

The diploid-like chromosome pairing in polyploid wheat is controlled by the Ph1 (pairing homoeologous) gene that is located on chromosome arm 5BL. By using a combination of cytogenetic and molecular techniques, we report the physical location of the Ph1 gene to a submicroscopic chromosome region (Ph1 gene region) that is flanked by the breakpoints of two deletions (5BL-1 and ph1c) and is marked by a DNA probe (XksuS1). The Ph1 gene region is present distal to the breakpoint of deletion 5BL-1 but proximal to the C-band 5BL2.1. Two other DNA probes (Xpsr128 and Xksu75) flank the region-Xpsr128 being proximal and Xksu75 being distal. The estimated size of the region is less than 3 Mb. The chromosome region around the Ph1 gene is high in recombination as the genetic distance of the region between 5BL-1 breakpoint and C-band 5BL2.1 (not resolved by the microscope) is at least 9.3 cM.     

Mapping of a mouse homolog of a Heterochromatin protein gene to the X Chromosome

Modifiers of position-effect-variegation inDrosophila are thought to encode proteins that are either structural components of heterochromatin or enzymes that modify these components. We have recently shown that a sequence motif found in oneDrosophila modifier gene, Heterochromatin protein 1 (HP1), is conserved in a wide variety of animal and plant species (Singh et al. 1991). Using this motif, termed chromo box, we have cloned a mouse candidate modifier gene,M31, that also shows considerable sequence homology toDrosophila HP1. Here we report evidence of at least four independently segregating loci in the mouse homologous to theM31 cDNA. One of these loci—Cbx-rsl—maps to the X Chromosome (Chr), 1 cM proximal toAmg and outside the X-inactivation center region.     

Mapping of a novel MEN-like syndrome locus to rat Chromosome 4

Multiple endocrine neoplasia-like syndrome (MENX) is a hereditary cancer syndrome in the rat characterized by inborn cataract and multiple tumors affecting the neuroendocrine system developed within the first year of life. The spectrum of affected organs is intermediate between MEN type 1 (MEN1) and MEN type 2 (MEN2) syndromes in human, but, in contrast to them, MENX is inherited in a recessive fashion. Here we report the mapping of the MENX locus to rat Chromosome (Chr) 4 by a genome-wide linkage analysis. This analysis was done in 41 animals obtained from a (Wistar/Nhg × SD^we) × SD^we interstrain backcross, where SD^we (Sprague-Dawley white eye) indicates the affected animals. The MENX disease locus was ultimately mapped to a ~22-cM interval on Chr 4 that includes the rat homolog of the human RET proto-oncogene. As activating point mutations of RET are known to be responsible for MEN2 in human, we analyzed several markers located in the proximity of Ret for linkage to the disease phenotype. Our data exclude Ret involvement in MENX and establish that a second gene, playing a role in endocrine tumor formation, lies within the distal part of rat Chr 4. Although heritable human endocrine tumors are quite rare, sporadic tumors of MEN-affected tissues occur at a much higher frequency, and their pathogenesis is poorly understood. The identification of the MENX gene should contribute to our understanding of the genetic mechanisms of neuroendocrine tissue tumorigenesis and may assist in developing new and more appropriate therapeutic strategies for these diseases.     

Chromosome Mapping in Staphylococcus aureus

The genome of Staphylococcus aureus was mapped by enumerating mutants induced by nitrosoguanidine during synchronous chromosomal replication following release from phenethanol inhibition. Both chromosomal replication time and cell division time were 120 min for this strain of S. aureus. Duplication of genes occurred within a 10-min period of the 120 min required for chromosomal replication. A high-resolution method was devised to determine the gene order of four genes that duplicated in the same 10-min interval of replication of the chromosome. A genomic map locating the positions of 10 genes was derived.     

Physical and Genetic Mapping of the SPO2 Prophage on the Chromosome of Bacillus subtilis 168

It has been found by density transfer and genetic mapping experiments that prophage SPO2 is linked to the antibiotic resistance marker ery-1 in Bacillus subtilis 168.     

Physical and Genetic Mapping of Chromosome 9s in Maize Using Mutations with Terminal Deficiencies

Deletion mapping was employed to determine the physical order of five morphological variants, pyd1, yg2, wd1, v28 and v31, with respect to restriction fragment length polymorphism (RFLP) markers located at the distal end of chromosome 9S in maize. The genetic materials used were a series of terminal-deficiency mutants, newly derived with MCCLINTOCK's original stocks developed in the 1940s, via break-age-fusion-bridge cycles. A combined physical map and genetic map has been constructed based on data gathered from both genetic complementation tests and RFLP analysis. The location of v31 in relation to RFLP markers was further determined by interval mapping. The physical distance between the healed telomeric end and the most distal RFLP marker in two terminal-deficiency lines was established by using pulsed field gel electrophoresis and verified by Bal31 digestion. The results from this study set a foundation for studies on the mechanism of healing of broken chromosome ends in higher plants.     

Physical Mapping of 2000 kb of the Mouse X Chromosome in the Vicinity of the Xist Locus

A physical map encompassing approximately 2.0 megabases (Mb) in the region of the mouse X-inactivation center has been constructed. The map extends from the Gjb-1 locus to the Xist locus and demonstrates the order of probes inseparable by genetic analysis. The deduced locus order is as follows: Gjb-1, Ccg-1, DXCrc171, Rps4, Phka, DXCrc177, DXCrc318, Xist . Detailed physical mapping in the region between the Phka and Xist loci indicates the position of CpG-rich islands associated with the 5′ end of genes. The DXCrc177 and DXCrc318 loci, both defined by probes derived from linking clones, are associated with CpG-rich islands. The map provides a framework for the isolation of underlying sequences in the mouse X-inactivation center region.