Somatic Instability Research Articles

The transposable element Tam1 of Antirrhinum majus is 17 kb long

The nivea locus of Antirrhinum majus encodes chalcone synthase, a key enzyme in anthocyanin biosynthesis. Genetic instability is known to occur at this locus. In vitro cloning and characterization of genomic DNA fragments from the unstable nivea-recurrens allele T53 revealed that the instability of nivea-recurrens is due to the presence of a 17 kb DNA insert in the nivea locus. Somatic instability leading to the variegated phenotype, i.e. highly spotted flowers, is due to frequent excision of the 17 kb Tam1 element (Transposon antirrhinum majus) during development of the plant. Excision of Tam1 is not tissue specific, but occurs with similar frequencies in leaves and blossoms.

Monoclonal antibodies reveal the structural basis of antibody diversity.

Hybridoma technology has made it possible to introduce into continuous culture normal antibody-forming cells and to obtain large amounts of the immunoglobulin produced by each of these cells. Examination of the structure of a number of monoclonal antibodies that react with a single antigen has provided new information on the structural basis of the specificity and affinity of antibodies. Comparisons of families of monoclonal antibodies derived from a single germ line gene revealed the importance of somatic mutation in generating antibody diversity. Monoclonal antibodies that react with variable regions of other monoclonals allow the further dissection and modulation of the immune response. Finally, the continued somatic instability of immunoglobulin genes in cultured antibody-forming cells makes it possible to determine the rate of somatic mutation and to generate mutant monoclonal antibodies that may be more effective serological reagents.

Somatic instabilities in wild isolates ofAspergillus nidulans

Somatic instabilities in wild isolates of<i>Aspergillus nidulans</i>

Somatic instabilities in wild isolates of Aspergillus nidulans

Somatic instabilities in wild isolates of Aspergillus nidulans

A comparison of the instabilities at the Nivea and Pallida loci in Antirrhinum majus

The unstable recurrens alleles of nivea and pallida have been compared for sensitivity to temperature during development. Previous work showed that the palrec allele mutates germinally and somatically with a greater frequency at 15° than at 25° C. The nivrec allele is less sensitive to temperature but somatic instability is still inversely correlated with temperature. There is no difference in germinal instability at the two temperatures for nivrec. The genetic stabiliser controls for palrec and nivrec are independent. Chemical mutagens and X-rays are ineffective in inducing changes in instability of either allele. Plants doubly homozygous for the two rec alleles and for the aurone producing sulfurea gene show that nivrec usually mutates prior to palrec; instances of palrec mutating first have possibly been seen but the flush that frequently occurs in plants homozygous for nivrec prevents a definite conclusion as to whether there is an obligate mutational sequence. An example of paramutation is described. Results vary according to the temperature at the time of the cross and during seed maturation, and depend on the direction of the cross; paramutagenic female parents induce a higher frequency of paramutants. Lines of varying paramutability and paramutagenicity have been established. Somatic paramutation in homozygous nivrec regularly occurs and varies with plant development.

Effects of low temperature on the somatic instability of an alien chromosome in Nicotiana tabacum

Effects of low temperature on the somatic instability of an alien chromosome in Nicotiana tabacum

Some Parameters of Respiratory Function in Normal and Abnormal Newborn Foals with Special Reference to Levels of paO2 during Air and Oxygen Inhalation

Two groups of foals, comprising normal and abnormal subjects were studied during the first week of life. The abnormal foals were selected from cases exhibiting clinical signs of somatic instability unassociated with bacterial infection. Measurements of respiratory rates, tidal and minute volumes and levels of pH, pCO2 and pO2 in arterial blood, were performed; a significantly increased respiratory rate and minute volume (p < 0.05), decreased tidal volume/kg. body weight and paO2 (p < 0.01) were found in the abnormal compared with the normal group. paO2 was significantly lower in the abnormal group after oxygen inhalation. It is suggested that a right to left shunt is present in foals which have difficulty in adapting to the extra-uterine environment. Further work is required to determine the size and position of the shunts and to assess their significance in the differential diagnosis of diseases affecting newborn foals.

SOMATIC AND MEIOTIC INSTABILITY OF R-STIPPLED, AN ALEURONE SPOTTING FACTOR IN MAIZE

SOMATIC AND MEIOTIC INSTABILITY OF <i>R</i>-STIPPLED, AN ALEURONE SPOTTING FACTOR IN MAIZE

Chromosome numerical mosaicism in some hybrids of theSolanum nigrum complex

The colchicine amphiploid (2n=72) of the hybridSolanum nodiflorum (2n=24)×S. villosum (2n=48) was crossed toS. memphiticum (2n=72) and toS. nigrum (2n=72). In the resulting F1 hybrids chromosome numerical mosaicism was observed in the anthers of some plants. It was found that chromosome mosaicism did not affect chromosome pairing in normal cells. Disharmonious gene combination seems to be responsible for premeiotic somatic instability which results in chromosome mosaicism observed during meiosis in pollen mother cells. Gene or genes for fertility are transmitted independent of those for chromosome stability. It is suggested thatS. nigrum andS. memphiticum possess in common a gene complex, which when combined withS. nodiflorum andS. villosum genomes will induce somatic instability.

Aneuploids in Seedling Populations of Tetraploid Alfalfa, Medicago sativa L.1

Frequencies of aneuploids in ‘Vernal’ and ‘Saranac’ alfalfa were 6% and 3%, respectively, at the time of seed germination. Aneuploids had 31 or 33 chromosomes, with only two exceptions. The effect of observed aneuploid frequencies on genetic ratios and estimates of double reduction was determined. These values would be only slightly affected if the aneuploidy were distributed over all eight sets of homologous chromosomes, but an erroneous double reduction estimate of 2‐5% would be obtained if one homologous set were preferentially involved. No somatic instability, accessory chromosomes, or fragments were observed in 209 plants examined.

SOMATIC INSTABILITY OF TELOCENTRIC CHROMOSOMES IN WHEAT AND THE NATURE OF THE CENTROMERE

SOMATIC INSTABILITY OF TELOCENTRIC CHROMOSOMES IN WHEAT AND THE NATURE OF THE CENTROMERE

A Mutable Gene System in Phaseolus vulgaris L.1

Variegated plants were observed in the F2 progeny of the Phaseolus vulgaris crosses ‘Yellow Eye PI 209086’ ✕ ‘G.N. Nebraska #1’ and ‘Dark Red Kidney’ ✕ G.N. Nebraska #1. In some environments a phenotypic ratio of 63 normal : 1 variegated plant was observed in the F2, while a 15:1 ratio was found in other enviromnents. The data suggest that the somatic instability which produced the variegated character was due to the action of two genes, one being unstable in the presence of a mutator gene. The third gene apparently had a threshold effect and was only expressed under some conditions. The environment‐sensitive gene was designated as “var,” the mutator gene as “mu,” and the unstable gene as “us.” Each of the parents lacked the mutator‐unstable gene complex for the development of the character. No variegated plants were found in the F2 of Dark Red Kidney ✕ PI 209806, which indicated that each of these parents possessed either the unstable gene or the mutator gene, but not both. Proposed crosses are discussed by which it is planned to distinguish whether G.N. Nebraska #1 carries the unstable gene or the mutator gene.

Somatic Instability Caused by a Cysteine-Sensitive Gene in Arabidopsis

A recessive gene immutans (im) is responsible for abnormal chloroplast development which results in variegation in Arabidopsis plants. Somatic mutability is simulated, though only functional disorder is involved. Cysteine and low temperature favor normal function, while homocysteine interferes with chloroplast development without producing an adverse effect on the growth of the mutant.

Somatic Instability in Derivatives from Agroelymus turneri Resembling Agropyron repens

Nielsen, E. L., and J. Nath. (U. Wisconsin, Madison.) Somatic instability in derivatives from Agroelymus turneri resembling Agropyron repens. Amer. Jour. Bot. 48(4): 345–349. Illus. 1961.—Variations in somatic chromosome numbers of 4 to over 80 were observed in root tip cells of Agropyron repens-like plants derived from Agroelymus turneri. The latter presumably had out-crossed to Agropyron repens. Split spindles in dividing nuclei and multinucleate cells were observed in the root tip meristem. The nuclear and mitotic behaviors observed can perhaps be attributed to an unbalanced ribonucleoprotein system resulting from the combination of distantly related genomes in the formation of the hybrid.

SOMATIC INSTABILITY IN DERIVATIVES FROM AGROELYMUS TURNERI RESEMBLING AGROPYRON REPENS

Nielsen, E. L., and J. Nath. (U. Wisconsin, Madison.) Somatic instability in derivatives from Agroelymus turneri resembling Agropyron repens. Amer. Jour. Bot. 48(4): 345–349. Illus. 1961.—Variations in somatic chromosome numbers of 4 to over 80 were observed in root tip cells of Agropyron repens‐like plants derived from Agroelymus turneri. The latter presumably had out‐crossed to Agropyron repens. Split spindles in dividing nuclei and multinucleate cells were observed in the root tip meristem. The nuclear and mitotic behaviors observed can perhaps be attributed to an unbalanced ribonucleoprotein system resulting from the combination of distantly related genomes in the formation of the hybrid.

CYTOGENETICS OF A TRISOMIC OF MATTHIOLA INCANA, INVOLVING A RING CHROMOSOME AND SOMATIC INSTABILITY OF SINGLENESS (VERSUS DOUBLENESS) OF FLOWERS AND SHAPE OF LEAVES

CYTOGENETICS OF A TRISOMIC OF MATTHIOLA INCANA, INVOLVING A RING CHROMOSOME AND SOMATIC INSTABILITY OF SINGLENESS (VERSUS DOUBLENESS) OF FLOWERS AND SHAPE OF LEAVES

GENETIC STUDIES OF A MOSAIC LEAF MUTANT

GENETIC STUDIES OF A MOSAIC LEAF MUTANT: Causing Somatic Instability in Cotton Get access CHARLES F. LEWIS CHARLES F. LEWIS Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Heredity, Volume 49, Issue 6, November 1958, Pages 267–271, https://doi.org/10.1093/oxfordjournals.jhered.a106825 Published: 01 November 1958

Somatic instability of chromosome number in Hymenocallis calathinum

Somatic instability of chromosome number in Hymenocallis calathinum

Genética de Coffea: XIX - Mutação somática afetando a côr das fôlhas em café

SUMMARY Somatic mutations usually found in Coffea arabica L. result in most cases from doubling or reduction in chromosome number. Gene instability in somatic tissues was reported for the na na and xc xc alleles which control, respectively, habit of growth and leaf size, and the color of the ripened fruits. No case of somatic instability of genes res­ponsible for the color of leaves has been reported previously. Young leaves of coffee plants are usually green or of a dark or light bronze color ; mature leaves are green. Leaves of plants of the variety purpurascens ( Coffea arabica L. var. purpurascens Cramer), however, present dark purple young leaves and slightly purple mature leaves. Purpurascens behaves as recessive to green. Among the progeny of a backcross (green x purpurascens) x purpurascens, a seedling was found that possessed normal green leaves except for two opposite branches arising from the same node. One of the branches was entirely purpurascens ; normal green and purpurascens areas could be seen in the mature leaves of the other. Since this plant had originally a non purpurascens phenotype, it should be a heterozygous

A black-blue dutch rabbit

A mosaic black-blue and white Dutch rabbit is reported. The condition was not transmitted to any of his 144 offspring. The possibility of the presence of genes controlling pigmentation in normally white areas is discussed, as also is the tendency for somatic instability being increased through inbreeding.