SEARCH · PubMed Health

Results for “mapping insertion sites”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources

PubMed1999

A YAC-based physical map of the mouse genome.

A physical map of the mouse genome is an essential tool for both positional cloning and genomic sequencing in this key model system for biomedical research. Indeed, the construction of a mouse physical map with markers spaced at an average interval of 300 kb is one of the stated goals of the Human Genome Project. Here we report the results of a project at the Whitehead Institute/MIT Center for Genome Research to construct such a physical map of the mouse. We built the map by screening sequenced-tagged sites (STSs) against a large-insert yeast artificial chromosome (YAC) library and then integrating the STS-content information with a dense genetic map. The integrated map shows the location of 9,787 loci, providing landmarks with an average spacing of approximately 300 kb and affording YAC coverage of approximately 92% of the mouse genome. We also report the results of a project at the MRC UK Mouse Genome Centre targeted at chromosome X. The project produced a YAC-based map containing 619 loci (with 121 loci in common with the Whitehead map and 498 additional loci), providing especially dense coverage of this sex chromosome. The YAC-based physical map directly facilitates positional cloning of mouse mutations by providing ready access to most of the genome. More generally, use of this map in addition to a newly constructed radiation hybrid (RH) map provides a comprehensive framework for mouse genomic studies.

Animals↗

PubMed1992

Restriction endonuclease analysis and mapping of the genomes of granulosis viruses isolated from Xestia c-nigrum and five other noctuid species.

Restriction endonuclease analysis was performed on the genomic DNA of granulosis viruses isolated from noctuid species of six genera: Xestia c-nigrum, Autographa gamma, Hydraecia amurensis, Celaena leucostigma, Aletia pallens and Pseudaletia separata. All of the isolates gave very similar restriction endonuclease profiles with only minor variations. An isolate obtained from X. c-nigrum was chosen as the reference genotype, and a genomic library was constructed for this isolate using plasmid vectors. The genome was mapped using EcoRI, BamHI and BglII, and Southern hybridization; the size of the genome was estimated to be 179 kbp. Hybridization of labelled clones to fragments of other isolates revealed that genotypic variation among isolates resulted from changes in restriction sites, and from deletion or insertion of DNA. Comparative restriction mapping revealed that all of the isolates were variants of one virus, even though they originated from different host species.

Animals↗

PubMed2005

Transmembrane topology of the protein palmitoyl transferase Akr1.

The two recently identified protein acyl transferases (PATs), Akr1p and Erf2p/Erf4p, point toward the DHHC protein family as a likely PAT family. The DHHC protein family, defined by the novel, zinc finger-like DHHC cysteine-rich domain (DHHC-CRD), is a diverse collection of polytopic membrane proteins extending through all eukaryotes. To define the PAT domains that are oriented to the cytoplasm and are thus available to effect the cytoplasmically limited palmitoyl modification, we have determined the transmembrane topology of the yeast PAT Akr1p. Portions of the yeast protein invertase (Suc2p) were inserted in-frame at 10 different hydrophilic sites within the Akr1 polypeptide. Three of the Akr1-Suc2-Akr1 insertion proteins were found to be extensively glycosylated, indicating that the invertase segment inserted at these Akr1p sites is luminally oriented. The remaining seven insertion proteins were not glycosylated, consistent with a cytoplasmic orientation for these sites. The results support a model in which the Akr1 polypeptide crosses the bilayer six times with the bulk of its hydrophilic domains disposed toward the cytoplasm. Cytoplasmic domains include both the relatively large, ankyrin repeat-containing N-terminal domain and the DHHC-CRD, which maps to a cytosolic loop segment. Functionality of the different Akr1-Suc2-Akr1 proteins also was examined. Insertions at only 4 of the 10 sites were found to disrupt Akr1p function. Interestingly, these four sites all map cytoplasmically, suggesting key roles for these cytoplasmic domains in Akr1 PAT function. Finally, extrapolating from the Akr1p topology, topology models are proposed for other DHHC protein family members.

Acyltransferases↗

PubMed1993

A three-dimensional model of the Cdc2 protein kinase: localization of cyclin- and Suc1-binding regions and phosphorylation sites.

The Cdc2 protein kinase requires cyclin binding for activity and also binds to a small protein, Suc1. Charged-to-alanine scanning mutagenesis of Cdc2 was used previously to localize cyclin A- and B- and Suc1-binding sites (B. Ducommun, P. Brambilla, and G. Draetta, Mol. Cell. Biol. 11:6177-6184, 1991). Those sites were mapped by building a Cdc2 model based on the crystallographic coordinates of the catalytic subunit of cyclic AMP-dependent protein kinase (cAPK) (D. R. Knighton, J. Zheng, L. F. Ten Eyck, V. A. Ashford, N.-H. Xuong, S. S. Taylor, and J. M. Sowadski, Science 253:407-414, 1991). On the basis of this model, additional mutations were made and tested for cyclin A and Suc1 binding and for kinase activity. Mutations that interfere with cyclin A binding are localized primarily on the small lobe near its interface with the cleft and include an acidic patch on the B helix and R-50 in the highly conserved PSTAIRE sequence. Two residues in the large lobe, R-151 and T-161, influence cyclin binding, and both are at the surface of the cleft near its interface with the PSTAIRE motif. Cyclin-dependent phosphorylation of T-161 in Cdc2 is essential for activation, and the model provides insights into the importance of this site. T-161 is equivalent to T-197, a stable phosphorylation site in cAPK. On the basis of the model, cyclin binding very likely alters the surface surrounding T-161 to allow for T-161 phosphorylation. The two major ligands to T-197 in cAPK are conserved as R-127 and R-151 in Cdc2. The equivalent of the third ligand, H-87, is T-47 in the PSTAIRE sequence motif. Once phosphorylated, T-161 is predicted to play a major structural role in Cdc2, comparable to that of T-197 in cAPK, by assembling the active conformation required for peptide recognition. The inhibitory phosphorylation at Y-15 also comes close to the cleft interface and on the basis of this model would disrupt the cleft interface and the adjacent peptide recognition site rather than prevent ATP binding. In contrast to cyclin A, both lobes influence Suc1 binding; however, the Suc1-binding sites are far from the active site. Several mutants map to the surface in cAPK, which is masked in part by the N-terminal 40 residues that lie outside the conserved catalytic core. The other Suc1-binding site maps to the large lobe near a 25-residue insert and includes R-215.

Amino Acid Sequence↗

PubMed1992

Epitope mapping of HIV-1 reverse transcriptase with monoclonal antibodies that inhibit polymerase and RNase H activities.

Lysates from E. coli expressing HIV-1 reverse transcriptase (RT) as a TrpE fusion protein were used for immunization of BALB/c mice. Twenty hybridomas producing monoclonal antibodies (MAbs) recognizing the RT part of the TrpE-RT fusion protein by Western blot analysis were isolated. Of these, 18 were reactive in immunofluorescence assays when tested on HIV-infected cells. Twelve MAbs were reactive with both the p66 and p51 fragments of RT, while 6 of the MAbs were reactive only with the p66 band, indicating specificity for the C-terminal (RNase H) region of RT. Mapping of the monoclonal antibody binding sites was performed using deletion and insertion mutants of recombinant RT. The antibodies bound to five distinct regions within amino acid sequences 190-560 of RT. In order to map functionally important regions of the RT molecule, the MAbs were tested for their ability to interfere with the polymerase and RNase H activities of the polypeptide. MAbs binding to two different epitopes in the polymerase domain were found to inhibit the polymerase activity. Of these, three MAbs also inhibited the RNase H activity. Two MAbs binding to the same epitope in the RNase H region inhibited RNase H activity and further mediated an effect on the polymerase activity.

Amino Acid Sequence↗

PubMed1988

On the specificity and effects on transcription of P-element insertions at the yellow locus of Drosophila melanogaster.

Fourteen P-element insertion mutants at the yellow (y) gene of D. melanogaster have been analysed by restriction mapping and DNA sequencing. The distribution of the insertion sites is nonrandom, with a preferred target site in the 5'-transcribed but non-translated leader of the gene. Transcription analysis indicates that P-elements inserted into the transcribed region of y can terminate y transcription. While the great majority of the P-element insertions into the preferred target site abolish y activity, this loss of activity is not due to disruption of the insertion site since imprecise excision events which do not restore the wild type sequence at the insertion site can restore y function. We further demonstrate that a mutant caused by a 221bp P-element insertion into the 5' transcribed but non-translated region, which show partial y activity, produces a larger mutant transcript consistent with it being a product of transcriptional readthrough. We present results which suggest that imprecise excision events which restore (or partially restore) y activity can occur by deleting P-element internal sequences which normally act to terminate y transcription.

Animals↗

PubMed1993

Mutation of Tyr697, a GRB2-binding site, and Tyr721, a PI 3-kinase binding site, abrogates signal transduction by the murine CSF-1 receptor expressed in Rat-2 fibroblasts.

The receptor for the myeloid cell growth factor colony stimulating factor 1 (CSF-1) is a protein tyrosine kinase that is closely related to the PDGF receptor. Ligand binding results in kinase activation and autophosphorylation. Three autophosphorylation sites, Tyr697, Tyr706 and Tyr721, have been mapped to the kinase insert domain. Deletion of the entire kinase insert domain completely abrogates signal transduction by the CSF-1 receptor expressed in Rat-2 fibroblasts. To investigate the function of individual phosphorylation sites present in the CSF-1 receptor kinase insert domain, a number of phosphorylation site mutants were expressed in Rat-2 fibroblasts. Mutation of either Tyr697 or Tyr721 compromised signal transduction by the CSF-1 receptor. A mutant receptor, in which both Tyr697 and Tyr721 were replaced by phenylalanine, has lost all ability to induce changes in morphology or to increase cell growth rate in response to CSF-1. Tyr721 has been identified recently as the binding site for PI 3-kinase. Here we report that GRB2 associates with the CSF-1 receptor upon ligand binding. The phosphorylation on tyrosine of SHC and several other GRB2-associated proteins increased upon stimulation with CSF-1. Tyr697 was identified as a binding site for GRB2. We suggest that PI 3-kinase, GRB2 and some of the GRB2-associated proteins could play an important role in signal transduction by the CSF-1 receptor.

Adaptor Proteins, Signal Transducing↗

PubMed2001

The effects of clonidine premedication and scalp infiltration of lidocaine on hemodynamic responses to laryngoscopy and skull pin head-holder insertion during skull base procedures.

This study was designed to determine if oral clonidine or lidocaine, injected into the scalp before head-holder (H-H) insertion, would attenuate the hemodynamic effects associated with intubation and H-H placement. Thirty-four patients undergoing skull base procedures were randomized to four groups. Group 1 received clonidine 5 mcg/kg po before surgery with 10 to 15 ml of 1% lidocaine infiltrated at pin insertion sites; Group 2 received clonidine with saline infiltration; Group 3 received a placebo preoperatively and had lidocaine infiltrated at pin sites; and Group 4 received a placebo with saline infiltrated. All patients had a standard anesthetic titrated to a 10 to 14 Hz EEG endpoint during laryngoscopy and H-H placement. Mean arterial pressure (MAP) was similar between groups during intubation, but heart rate (HR) increased in patients who did not receive clonidine. H-H application increased HR and MAP in Group 4. HR also increased after H-H placement in patients who received oral clonidine, while patients receiving scalp lidocaine or both clonidine and scalp lidocaine had little change in either value. Clonidine attenuated HR increases after laryngoscopy but not after H-H placement. Lidocaine injected at the pin sites reduced HR, and MAP increased after H-H insertion. The combination of oral clonidine and scalp lidocaine blunted hemodynamic responses to both intubation and H-H placement.

Journal Article↗

PubMed2003

Resources for targeted insertional and deletional mutagenesis in Arabidopsis.

The maize transposons Activator (Ac) and Dissociation (Ds) are active in many monocots and dicots, including Arabidopsis. We describe a new Ac-derived transposon construct, designated the Ds-loxP T-DNA, which can be used for both insertional and deletional mutagenesis. There are loxP sites in both orientations on both the transposon and the donor site T-DNA and an arrangement of marker genes that permits selection of transposition events, as well as deletions and inversions extending from the donor site to a transposon reinserted on either side of it. We show that Cre-mediated deletions and inversions occur at a high frequency. The tendency of Ac-Ds transposons to reinsert near the donor site can be used to target both insertional and deletional mutagenesis, but efficient exploitation of this property requires a library of mapped marked donor sites distributed in the genome. We have created a population of independent Ds T-DNA transformants and we have mapped an initial set of 75 Ds T-DNA integration sites. We assessed the potential efficiency of targeted mutagenesis by detecting Ds reinsertion events at several loci over a 400 kb interval from each of two donor sites with different Ds T-DNA constructs. The distribution of reinsertion sites is similar around the two tested loci, with roughly 10, 4, and ca. 1% of reinsertions detected within 1-2 kb of sites 10, 100, and 200-400 kb from the donor site, respectively. To facilitate the use of this targeted mutagenesis system. we have constructed a searchable database of the mapped Ds T-DNA integration sites.

Arabidopsis↗

PubMed1994

Transgenic tomato lines containing Ds elements at defined genomic positions as tools for targeted transposon tagging.

We have introduced a genetically marked Dissociation transposable element (DsHPT) into tomato (Lycopersicon esculentum) by Agrobacterium tumefaciens-mediated transformation. Probes for the flanking regions of the T-DNA and transposed DsHPT elements were obtained with the inverse polymerase chain reaction (IPCR) technique and used in RFLP linkage analyses. The RFLP map location of 11 T-DNAs carrying DsHPT was determined. The T-DNAs are distributed on 7 of the 12 tomato chromosomes. To explore the feasibility of gene tagging strategies in tomato using DsHPT, we examined the genomic distribution of DsHPT receptor sites relative to the location of two different, but very closely linked, T-DNA insertion sites. After crosses with plants expressing Ac transposase, the hygromycin phosphotransferase (HPT) marker on the Ds element and the excision markers beta-glucuronidase (GUS) and Basta resistance (BAR) facilitated the identification of plants bearing germinally transposed DsHPT elements. RFLP mapping of 21 transposed DsHPT elements originating from the two different T-DNA insertions revealed distinct patterns of reintegration sites.

Agrobacterium tumefaciens↗

PubMed1989

Constructing chromosome- and region-specific cosmid maps of the human genome.

A chromosome-specific ordered set of cosmids would be a significant contribution toward understanding human chromosome structure and function. We are developing two parallel approaches for creating an ordered cosmid library of human chromosome 19 and other selected subregions of the human genome. The "bottom up" approach is used to establish sets of overlapping cosmids as islands or "contigs" along the chromosome, while the "top down" approach, using pulsed-field gel electrophoresis and yeast cloning, will establish a large-fragment map and close the inevitable gaps remaining from the "bottom up" approach. Source DNA consists of a single homolog of chromosome 19 from a hamster--human hybrid cell and human fragments cloned in yeast artificial chromosomes. We have constructed cosmid libraries in a vector that facilitates cloning small amounts of DNA, allows transcription of the insert termini, and contains unique sites for partial-digest mapping. Computer simulations of cosmid contig building suggest that near-optimal efficiency can be achieved with high-density restriction fragment digest schemes that can detect 20-30% overlap between cosmids. We developed the chemistry and data analysis tools to compare the ordering efficiencies of several cosmid restriction digest fingerprinting strategies. Restriction fragments from a four-cutter digest are labeled with a fluorochrome, separated by polyacrylamide gel electrophoresis, and detected after laser excitation as they traverse a fixed point in the gel. We have also developed the software to rapidly process the output signal to define and analyze the fragment peaks. Up to three cosmids (or three different digests of the same cosmid) plus a size standard are analyzed simultaneously in a single gel lane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1982

Isolation and chromosomal localization of unique DNA sequences from a human genomic library.

Recombinant bacteriophage lambda from a human genomic library were screened to indentify human DNA inserts having only unique sequences. Unique human inserts were found in about 1% of the phage screened. One recombinant phage, P3-2, was studied in detail. It contains a human insert of 14.7 kilobases with four internal EcoRI cleavage sites. A restriction map was constructed for EcoRI and BamHI sites. Hybridization of the 32P-labeled P3-2 probe to a Southern blot of EcoRI-digested total human DNA yielded distinct bands at positions corresponding to the human insert fragments contained in P3-2. By using a series of human-Chinese hamster somatic cell hybrids containing unique combinations of human chromosomes, the human DNA segment in phage P3-2 was assigned to human chromosome 22 by blot hybridization and synteny analysis. In addition, another human DNA segment, 11.4 kilobases, in phage P3-10 was assigned to human chromosome 10 by similar procedures. With this approach, more unique DNA sequences can be isolated, assigned to specific human chromosomes, and used as genetic markers for gene mapping and linkage, polymorphism, and other genetic studies in the human genome.

Animals↗

PubMed1989

Analysis of the Om(1D) locus in Drosophila ananassae.

From the ca;px stock, which is the progenitor of Om mutants caused by insertions of the tom retrotransposon, 50 kb of genomic DNA including the Om(1D) locus was cloned by tom tagging and chromosome walking. Southern blot analyses of six Om(1D) mutants exposed one or two tom elements inserted at five nonrandom sites within an 18-kb distal segment of the restriction map; the phenotypic uniformity between these mutants was not affected by variations in the position, number or orientation of their inserts. Spontaneous revertants or more extreme derivatives of Om(1D) alleles were nonlinearly associated with losses or gains of tom inserts. Seven of eight radiation induced derivatives of Om(1D) mutants had one breakpoint of a chromosome rearrangement in polytene section 13A which includes the Om(1D) locus. Two Om(1D) derivatives, a spontaneous revertant and an induced extreme allele, were associated with overlapping deficiencies which define a region that is likely to contain the Om(1D) coding seguences proximal to the tom insertion sites. Incidental results confirm the previously indicated homology of the Om(1D) locus with the Bar locus of Drosophila melanogaster.

Animals↗

PubMed1996

Frequent loss of chromosome 8p in hepatitis B virus-positive hepatocellular carcinomas from China.

The majority of hepatocellular carcinomas (HCCs) from hepatitis B virus (HBV)-endemic areas contain integrated viral sequences. To better understand the role of HBV DNA insertion in tumorigenesis, we examined the integration site of a HCC harboring a single insert. Cellular DNAs flanking the viral sequences were mapped to chromosomes 17 and 8, indicating a translocation had occurred at the site of viral integration. Regional mapping of chromosome 17 demonstrated that HBV had integrated in 17p12-pter, a region that harbors the p53 tumor suppressor gene. Many studies have shown that chromosome 17p allele loss occurs frequently in HCCs from certain geographical areas. To investigate the chromosome 8 allele status in Chinese HCCs, a panel of 37 matched normal and HCC DNAs from Qidong, China was analyzed for tumor-specific allele loss with RFLP probes from both arms of chromosome 8. Tumor-specific loss of heterozygosity was highest on the short arm with 71.4% (10/14) and 85.0% (17/20) of the informative patients missing an allele for 8p23 (YNM3) or 8p21 (NEFL), respectively. Allele loss from the long arm of chromosome 8 was also observed with 30.0% (6/20) and 33.3% (7/21) of the samples informative for 8q22 (CA2) and 8q24 (MCT128.2), respectively. The high allele loss on 8p correlates with recent studies of other human cancers and is interpreted to indicate that a tumor suppressor gene(s) whose loss is important for carcinogenesis lies within this region. These findings also support a model in which HBV insertions associated with gross chromosomal changes can identify genomic regions where alteration is important for development of some HCCs.

Carcinoma, Hepatocellular↗

PubMed2002

Chromosome assignment of Cd36 transgenes in two rat SHR lines by FISH and linkage mapping of transgenic insert in the SHR-TG19 line.

The chromosome position of the Cd36 insert was determined by FISH in two rat transgenic lines (SHR/Ola-TgN(EF1aCd36)10Ipcv (SHR-TG10) and SHR/Ola-TgN(EF1aCd36)19Ipcv (SHR-TG19). The Cd36 transgene construct labelled with digoxigenin-11-dNTP was used as a probe in the FISH analysis. In accord with the previous finding that the SHR-TG10 harbours 6-8 copies of the transgene, the signals from both metaphase and interphase nuclei of SHR-TG10 preparations were rather strong and the probe hybridized to both copies of chromosome 1 at band q55. The probe hybridization to SHR-TG19 metaphase preparations also showed homozygosity of the transgene with localization of both copies to chromosome 11 at band q11. The signals were distinct but much weaker compared to the SHR-TG10, which again is in accord with the fact that the SHR-TG19 line harbours only a single copy of the transgene. In order to look for a possible impact of the insertion site neighbourhood upon the transgene phenotypic effect, we performed linkage mapping of the transgene in the SHR-TG19 line. By linkage mapping, the placement of the transgene to the proximal part of RNO11 was confirmed, the critical interval being 4 cM between D11Rat20 and D11Rat21, in good agreement with the RH map. Within the close neighbourhood of the inserted Cd36 transgene, there are several genes known to be expressed in kidney, and so the influence of some regulatory sequences enhancing kidney expression of the Cd36 transgene can be envisaged.

Animals↗

PubMed2004

Mapping of transposable element Dissociation inserts in Brassica oleracea following plant regeneration from streptomycin selection of callus.

To investigate the potential of heterologous transposons as a gene-tagging system in broccoli (Brassica oleracea var. italica), we have introduced a Dissociation ( Ds)-based two-element transposon system. Ds has been cloned into a 35S-SPT excision-marker system, with transposition being driven by an independent 35S-transposase gene construct. In three successive selfed generations of plants, there was no evidence of germinal-excision events. In a previous study, we overcame this apparent inability to produce B. oleracea plants with germinal excisions by performing a novel tissue-culture technique to select for fully green shoots from seed with somatic excision events. The results showed a very high efficiency of regeneration of fully green plants (up to 65%), and molecular analysis showed that the plants contained the equivalent of a germinal-excision event. In this study, we followed the previous work by using inverse and nested PCR to generate probes of flanking genomic DNA adjacent to independently reinserted Ds elements, and these were hybridised to DNA from a double-haploid mapping population of B. oleracea. Seventeen Ds insertions and the original Ds T-DNA site have been localised, and these are spread over six (out of nine) linkage groups. Distribution of inserts show that 15 were found on a different linkage group to the original 'launch' site, and of these 11 were found to be clustered on two separate groups. Previous studies in other plant species have found that germinal excision of Ds predominantly moves to sites linked close to the donor site. However, this study shows a potential to produce plants with Ds insertion scattered over many unlinked sites.

Blotting, Southern↗

PubMed1998

The psychrotrophic bacterium Yersinia enterocolitica requires expression of pnp, the gene for polynucleotide phosphorylase, for growth at low temperature (5 degrees C).

The psychrotrophic bacterium Yersinia enterocolitica is characterized by temperature-dependent adaptations. To investigate Y. enterocolitica genes involved in cold adaptation, a mutant restricted in its ability to grow at 5 degrees C was isolated from a transposon mutant library. The transposon insertion site in this psychrotrophy-defective (PD) mutant mapped 16 bp upstream of an open reading frame whose predicted amino acid sequence showed 93% similarity with the Escherichia coli exoribonuclease polynucleotide phosphorylase (PNPase), encoded by pnp. Expression of this gene was blocked in the PD mutant. However, the introduction of a second copy of pnp, including 0.33 kbp sequences upstream of its coding region, into the chromosome of the PD mutant restored pnp expression as well as the ability to grow at 5 degrees C. Furthermore, the expression of pnp appeared to be temperature dependent: in the parental Y. enterocolitica strain, the levels of both pnp mRNA and PNPase were 1.6-fold higher at 5 degrees C compared with 30 degrees C. A similarly enhanced level of PNPase at 5 degrees C was observed in the merodiploid recombinant strain, which indicates that the 0.33 kbp region upstream of pnp harboured a cold-inducible promoter. A putative cold shock promoter motif (ATTGG) was observed in this region.

Base Sequence↗

PubMed1980

Identification of a novel genetic element in Escherichia coli K-12.

Induction of the SOS repair processes of Escherichia coli K-12 caused a 14.4-kilobase species of circular deoxyribonucleic acid, called element e14, to be excised from the chromosome. To aid further characterization of this species, an 11.6-kilobase segment of e14 was inserted into the HindIII site of plasmid pBR313. To map e14 on the E. coli K-12 chromosome, the recombinant plasmid, pAG2, was used to transform a polA recipient, an event which required integration of pAG2 into the recipient chromosome. This recombinational event was dependent upon the region of homology between the incoming plasmid and the chromosome, as no transformants were scored when either a strain cured of the element was the recipient or pBR313 was the transforming deoxyribonucleic acid. Using these transformants, we have shown that e14 maps between the purB and pyrC loci near min 25. Several strains of E. coli K-12 were found to contain e14; however, one strain, Ymel trpA36, did not. In addition, e14 was found to be absent in both E. coli B/5 and E. coli C. The approach to mapping developed for this work could be used to map other fragments of E. coli deoxyribonucleic acid which have no known phenotype.

Chromosome Mapping↗