Order Of Loci Research Articles

Gene order and localization of enzyme loci on the short arm of chromosome 1.

SummaryAnalysis of hybrids containing different rearrangements involving human chromosome 1 suggests that GDH and ENO1 are distal to PGD, and that all 3 loci are distal to 1p36.13. Evidence is presented indicating that FUCA and AK2 are in 1p34.

Studies on the E. coli groNB (nusB) gene which affects bacteriophage lambda N gene function.

Escherichia coli mutants, called groNB, which block the growth of bacteriophage lambda at the level of action of the gene N product, have been isolated as survivors at 42 degrees C of bacteria carrying a) the defective prophage lambda bio11 i lambda cI857 delta H1 or b) the pcR1 plasmid containing the EcoRI immunity fragment of phage lambda cI857. In addition, groNB bacterial mutants have been isolated at 37 degrees C, as large colony formers in the presence of lambda i lambda cI h434, lambda i lambda cI h lambda, and lambda i lambda cI h80 phage. The groNB locus is located at 9 minute of the E. coli genetic map with the order of the neighboring loci being proC tsx groNB purE. Most groNB mutations isolated at 42 degrees C were found to interfere in addition with bacterial growth at low temperatures, since (a) the GroNB phenotypes of lambda growth inhibition and bacterial cold sensitivity cannot be separated by P1 transduction, and (b) some cold resistant revertants simultaneously become Gro+ for lambda growth. Lambda transducing phages carrying the groNB+ bacterial gene have been isolated. GroNB mutant bacteria lysogenized by the transducing phage acquire the Gro+ phenotype and simultaneously the cold resistant phenotype, suggesting that the groNB mutations are recessive to the wild-type gene.

Regulation of fatty acid degradation in Escherichia coli: isolation and characterization of strains bearing insertion and temperature-sensitive mutations in gene fadR.

Transposon Tn10 was used to mutagenize the fadR gene in Escherichia coli. Mutants bearing fadR:Tn10 insertion mutations were found to (i) utilize the noninducing fatty acid decanoate as sole carbon source, (ii) beta-oxidize fatty acids at constitutive rates, and (iii) contain constitutive levels of the five key beta-oxidative enzymes. These characteristics were identical to those observed in spontaneous fadR mutants. The constitutive phenotype presented by the fadR:Tn10 mutants was shown to be genetically linked to the associated transposon-encoded drug resistance. These results suggest that the fadR gene product exerts negative control over the fatty acid degradative regulon. The fadR gene of E. coli has been mapped through the use of transposon-mediated fadR insertion mutations. The fadR locus is at 25.5 min on the revised map and cotransduces with purB, hemA, and trp. Three-factor conjugational and transductional crosses indicate that the order of loci in this region of the chromosome is purB-fadR-hemA-trp. Spontaneous fadR mutants were found to map at the same location. Strains that exhibit alterations in the control of the fad regulon in response to changes in temperature were also isolated and characterized. These fadR(Ts) mutants were constitutive for the fad enzymes at elevated temperatures and inducible for these activities at low temperatures. The fadR(Ts) mutations also map at the fadR locus. These results strongly suggest that the fadR gene product is a repressor protein.

A reciprocal translocation induced in an oocyte and affecting fertility in male mice

The reciprocal translocation <i>T(5;12)31H, </i>induced by irradiation of oocytes, causes sterility in most heterozygous male carriers, a tenfold reduction in mean sperm count, and a high frequency of abnormal sperm. Chromosome breakpoints are in bands 5B and 12F1, leading to a long (12<sup>5</sup>) and a short (5<sup>12</sup>) marker chromosome. Ninety five percent of germ cells showed chain quadrivalents or trivalents at meiotic metaphase I (MI). The order of loci on chromosome 5 is centromere—<i>T31H</i>—<i>Rw</i>—<i>go </i>with a recombination frequency of 31 + 7% between <i>T31H </i>and <i>Rw</i>. No linkage was found between <i>T31H </i>and linkage group XVI genes previously assigned to chromosome 12; it was concluded that they are located elsewhere. Viable tertiary monosomic and trisomic young (lacking the 5<sup>12</sup> region or with it in excess) were generated with post-natal frequencies of 4.5% and 14.6%, respectively, from outcrosses of heterozygous females. A deficiency of monosomics was also found in 11½ to 14½ day foetuses, when abnormal phenotypes or severe retardation produced by other unbalanced karyotypes were found. There was also a marked deficiency of monosomic offspring from outcrossed monosomic mothers, only 16.1% being found, whereas trisomic mothers gave 52.8% trisomic young. Surviving monosomics of both sexes were smaller than trisomics at birth and tended to have unusual skeletal fusions. Both types of aneuploid male were sterile, but tertiary monosomics were less severely affected, as judged by testis mass, sperm counts, and the appearance of testis sections. Both tertiary monosomic and trisomic females have smaller litters than normal females. Possible reasons for these findings are discussed, as well as recent observations throwing light on mechanisms of sterility in this type of translocation.

Linkage analyses of murine immunoglobulin heavy chain and serum prealbumin genes establish their location on chromosome 12 proximal to the T (5;12) 31H breakpoint in band 12F1.

Analysis of backcross mice carrying the Harwell translocation T(5;12)31H has led to the definitive localization of the immunoglobulin heavy chain gene cluster. Both Igh-1 and Pre-1 loci were found to segregate in tight linkage with the chromosomal markers 5(12) and 12(5), which define the balanced translocation T(5;12)31H. Additional data establish the location of these genes at the telomeric end of chromosome 12. That both loci are proximal to the chromosomal breakpoint in band 12F1 is shown by the phenotypes of segregants aneuploid for the presence or absence of the small marker 5(12). The order of loci inferred from a single recovered recombinant is: centromere-Igh-1-Pre-1-T(5;12)31H.

Fine structure of the 21S ribosomal RNA region on yeast mitochondrial DNA

1. We have determined the physical location of mitochondrial genetic markers in the 21S region of yeast mtDNA by genetic analysis of petite mutants whose mtDNA has been physically mapped on the wild-type mtDNA. 2. The order of loci, determined in this study, is in agreement with the order deduced from recombination analysis and coretention analysis except for the position of omega+: we conclude that omega+ is located between C321 (RIB-1) and E514 (RIB-3). 3. The marker E514 (RIB-3) has been localized on a DNA segment of 3800 bp, and the markers E354, E553 and cs23 (RIB-2) on a DNA segment of 1100 base pairs; both these segments overlap the 21S rRNA cistron. The marker C321 (RIB-1) has been localized within a segment of 240 bp which also overlaps the 21S rRNA cistron, and we infer on the basis of indirect evidence that this marker lies within this cistron. 4. In all our rho+ as well as rho- strains there is a one-to-one correlation between the omega+ phenotype, the ability to transmit the omega+ allele and the presence of a mtDNA segment of about 1000 bp long, located between sequences specifying RIB-3 and sequences corresponding to the loci RIB-1 and RIB-2. This segment may be inserted at this same position into omega- mtDNA by recombination. 5. The role which the different allelic forms of omega may play in the polarity of recombination is discussed.

Physical mapping of the yeast mitochondrial genome

(1) We have derived a fine-structure map of the 70 kb mitochondrial genome of the yeast S. cerevisiae, strain D273-10B, and compared it with our previous maps for strain MH41-7B. Restriction fragment maps for 56 enzyme recognition sites for 13 endonucleases, Eco RI, Hpa I, Bam HI, Hha I, Hinc II, Xba I, Hind III, Bgl II, Pvu II, Sal I, Pst I, Sst I, and Xho I, have been derived. We have used several methods to obtain these maps: (a) Four enzymes (Sal I, Sst I, Xho I, Pst I), each of which cuts D273-10B mtDNA at a single site, were employed to localize and orient fragments from multi-site enzyme digests that are cleaved by the single-site enzyme. (b) Radioactively labeled probes (rRNA or copy RNA [cRNA] transcribed from simple-sequence petite mtDNA) were hybridized to restriction fragments from different digests for identification of fragments which share common sequences. (c) The products of double or triple enzyme digests were identified for mapping and confirmation of the localization of restriction sites. (2) The antibiotic-resistant (antR) loci for erythromycin (E), chloramphenicol (C), paromomycin (P), and oligomycin (OI, OII) were positioned on the physical restriction map by hybridization of 3H-labeled cRNA transcribed from simple-sequence petite mtDNAs that retain a single genetic antR marker to appropriate restriction fragments bound to nitrocellulose filters. (3) Mitochondrial transcripts (21s rRNA, 14s rRNA, and tRNAs) labeled with 125I were hybridized to restriction fragments for identification of the corresponding coding sequence. (4) The gene order and localization of the antR loci and mitochondrial transcripts are as follows: C(0-1.5u)-tRNA I(0-21.5u)-P(29-36.6u)-tRNA II(29-46.4u)-14s rRNA(36-38.3u)-OII(60.3-62.5u) - tRNA III(73-76u) - OI(78.6-83.0u) - tRNA IV(82.5-83.0u) - E(94.2-98.6u) - 21s rRNA (94.2-99.4u). (5) The DNA fine structure and gene map of the 70 kb D273-10B mtDNA were compared to the map of the larger MH41-7B (76 kb) mtDNA. There are 56 restriction sites on D273-10B and 67 sites on MH41-7B for the 13 enzymes studied. The additional restriction sites are largely accounted for by the presence, in MH41-7B, of two sets of sequences, "A" (2.7 kb) and "B" (3.0 kb), located on either side of the OII marker. The remainder of the fragments map is remarkably similar for the two strains. The distances separating the antR loci and the mitochondrial transcripts are very similar except in the two regions surrounding OII.

Linkage group I: a statistically significant locus order from family studies.

Linkage group I: a statistically significant locus order from family studies.

Mechanical Couplings—A General Geometrical Theory, Part 1: Theorems on Algebraic Loci and Couplings

In the broad category of couplings considered the two coupled bodies have either one or two relative degrees of freedom. Points, planes, and lines guided by such couplings trace a variety of spatial loci restricted by the requirement that they must all be algebraic. The order, class, or degree of such loci is related to the tracing element, and is proved to be always exactly identifiable with an invariant property of a particular coupling, here called the “feather” of the coupling. This property is central to two new theorems which unify many hitherto distinct facets of linkages. Some shortcuts are revealed to assist in more detailed study of mechanical movements.

SPATIO‐TEMPORAL INTEGRATION IN READING TACHISTOSCOPICALLY PRESENTED WORDS

ABSTRACTIt has been suggested that there is a visual encoding of a verbal stimulus which outlasts the duration of the icon. An attempt is made to determine what the characteristics of such an encoded representation are. The present experiment attempts to demonstrate that spatio‐temporal information is utilized in the encoding processes necessary for word recognition. The letters of words are presented over successive tachistoscopic exposures which subjects are instructed to either integrate in terms of the temporal order of input or in terms of the spatial location. The central finding indicates that word recognition latencies are significantly elevated by the existence of an interpretation of the stimulus resulting from integration of the uninstructed form. The findings offer a demonstration of a stable memory matrix capable of representing alphabetic characters in terms of identity as well as spatial locus and temporal order of input.

Linkage of GLO with HLA and Bf. Effect of population and sex on recombination frequency.

Further data on the linkage relationships of red cell glyoxalase I(GLO) with HLA and Bf are reported. The most likely order of loci is GLO: Bf: HLA-B: HLA-A. No sex difference in the frequency of recombination between GLO and HLA was noted, but recombination was more frequent for both males and females in the American black population than in the white population.

A new intersex in Culex pipiens L. (Diptera: Culicidae). II. Inheritance.

Data are presented which indicate that the recombination frequency for M (maleness) and w (white-eye) is 0.0160 ± 0.0097; that of w and c (intersex) is 0.0249 ± 0.0091. The order of loci is m-w-c. The gametic viabilities of dominant alleles to their recessive counterparts were 1.0046 ± 0.0132 for the sex locus, 1.0265 ± 0.0139 for the w locus, and 1.0045 ± 0.0059 for the c locus. The suppression of double crossovers was estimated at 92% over the chromosome segment from M to c.

The use of lod scores for the determination of the order of loci on a chromosome

A method is given for calculating the probabilities of the possible gene orders for a group of syntenic loci using lod scores calculated for each pair of loci in the group. Applying it, we find the most probable gene order for the five loci on chromosome 1 to be PGM1; Rh; PGD; PEP-C; Fy. However, the probabilities for other orders such that Rh lies between PGM1 and PGD with PEP-C and Fy outside these three are of a similar order of magnitude and no firm conclusions can be given. The probability for other possible orders is negligible.

Mutants of Escherichia coli defective in membrane phospholipid synthesis: mapping of the structural gene for L-glycerol 3-phosphate dehydrogenase.

The structural gene for the biosynthetic l-glycerol 3-phosphate dehydrogenase has been mapped at min 71.5 on the Escherichia coli chromosome. This gene (gpsA) is co-transduced with the xyl, mtl, and pyrE loci. Three-factor conjugational crosses and the transduction data indicate that the order of loci in this region of the chromosone is mtl, gltE, gpsA, gadR, gadS, pyrE. Study of a temperature-sensitive gpsA mutant possessing a dehydrogenase of increased thermolability indicated that gpsA is the structural gene for the dehydrogenase. All dehydrogenase-deficient strains tested were mapped very close to the gpsA locus. Attempts at genetic complementation analysis were unsuccessful.

Transductional analysis of the leu-thr region of chromosome of Serratia marcescens.

Transductional analysis of the chromosomal linkage map of Serratia marcescens near leu revealed the following order of loci: ser4-thr3-pyr1-pdx2-leu1-azi8.

Mutants d'Escherichia coli K 12 affectés pour leur croissance sur méthyl-β-D-glucuronide: Localisation du gène de structure de la β-D-glucuronidase (uid A)

Mutants of E. coli K 12 unable to grow on a β-D-glucuronide (methyl-β-D-glucuronide) and yet able to grow on hexuronates have been isolated; they are deficient for the enzyme: β-D-glucuronidase. By conjugation and transduction experiments, these mutations have been mapped in a locus uid A between man and aro D. No or weak cotransduction is found between aro and man: man is shifted from its precedent location to 30.5 minute very close to uid A (linked by 83 to 97% of cotransduction). The order of loci in this region appears to be: ... phe S...pps...aro D...uid A...man.... Some of these mutations can reverse to wild type with a thermosensitive glucuronidase. These reverse mutations are found linked to this locus uid A; these results strongly suggest that uid A is the site of the structural gene of β-glucuronidase.

The T6 translocation in the mouse: its use in trisomy mapping, centromere localization, and cytological identification of linkage group 3.

The occurrence of hairless piebald mice trisomic for the chromosome segments of the T6M chromosome has shown that the LG III loci hr and s are not located on T6M. The T6 breakpoint in LG III is therefore in the position hr-s-T6. T6M must carry the gene Fkl, which is located on the far side of the T6 breakpoint from hr in LG III.-T6 reduces recombination in the hr-s region.-Trisomy for the chromosome segments of the T6M chromosome appears to severely reduce viability.-The gene hr has been shown to lie between the centromere and the T6 breakpoint. The order of loci in LG III is therefore: centromere-hr-s-T6.-Equations are given for the relation between the frequency of adjacent-2 segregation and the frequency of recovery of complementation zygotes for the case in which the translocation heterozygote can form either quadrivalent or univalent-trivalent configurations at meiosis.-Linkage Group III is carried on chromosome 14. LG VI is the other linkage group involved in T6, and is carried on chromosome 15.

Loci differentially affected by selection in two American black populations.

The hypothesis that loci differentially affected by selection can be identified was tested by a comparison of two American black populations. The hypothesis had previously been studied in Evans County, Georgia and the data from that study were compared with data obtained from the population of Sapelo Island, Georgia. In both, gene frequencies for 21 polymorphic systems were determined. Estimates were made for 14 of these traits of the gene migration (m) from whites into these black populations, by use of the equation: m = (q(n) - q(Af))/(q(w) - q(Af)), where q(w), q(n), and q(Af) are the frequencies of an allele in the white, black, and West African populations, respectively. In this calculation, it is assumed that the differences in gene frequencies between American blacks and Africans are due entirely to gene mixture. On this assumption, if only gene mixture were operating, the values of "m" determined for each locus would be about the same. If "m" has a different value at some loci than it has at others, then selection for traits controlled by genes segregating at these loci could account for this difference. Values of "m" in both populations were scattered. These values were ranked for each population and the rank orders compared. There was a highly significant association between the rank order of loci in the two populations. This finding supports the hypothesis that loci differentially affected by selection can be identified, and that the selective forces have operated on the same loci in both populations.

Location and orientation of the phoA locus on the Escherichia coli K-12 linkage map.

The order of gene loci in the phoA-phoR region of the Escherichia coli K-12 linkage map was demonstrated to be lac phoA proC phoR. The end of the phoA locus corresponding to the amino terminus of alkaline phosphatase was shown to be the end nearer proC. Translation (and transcription) of phoA is therefore in the anticlockwise direction relative to the conventional E. coli linkage map.

A new genetic locus mapped from behavioral variation in mice: audiogenic seizure prone (ASP).

Audiogenic seizure susceptibility to the initial presentation of intense sound was studied in generations of mice derived from the susceptible DBA/2J and the resistant C57BL/6J inbred strains. The experimental results led to the detection, location, and position of a new genetic locus affecting behavior in mice. The locus is designatedasp (audiogenic seizure prone), and the pattern of inheritance for high seizure risk is recessive. Evidence for the mapping ofasp results from the following experimental findings: (1) frequencies of seizures for each of six segregating generations obtained by crossing C57BL/6J and DBA/2J conformed to expectations based upon a single locus model of genetic inheritance; (2) theasp-locus is loosely linked to theb-locus and thus resides on Linkage Group VIII of the mouse; (3) linkage relationships betweenasp and other named mutations on LG VIII, pintail (Pt),misty (m), brown (b), and autosomal glucose-6-phosphate dehydrogenase (Gpd-1), indicate that the position of theasp-locus is towards the centromeric end of the chromosome. The order of loci isasp-b-Pt-Gpd-1; (4) no linkage was observed betweenasp and thed-locus of Linkage Group II. These experiments illustrate that new genetic loci, whose allelic alternatives exert major effects on chosen behavioral characters, can be identified and mapped in a directed search.