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131.
132.
Dennis WM. Stevenson 《Brittonia》1992,44(2):220-223
My previously published provisional classification of the Cycadales is here formally published. This classification is based upon a cladistic analysis of characters ranging from gross morphology to phytochemistry. Encephalartos is lectotypified. 相似文献
133.
Bo Chang Richard S Smith Maureen Peters Olga V Savinova Norman L Hawes Adriana Zabaleta Steven Nusinowitz Janice E Martin Muriel L Davisson Constance L Cepko Brigid LM Hogan Simon WM John 《BMC genetics》2001,2(1):1-12
Background
Glaucoma is a common disease but its molecular etiology is poorly understood. It involves retinal ganglion cell death and optic nerve damage that is often associated with elevated intraocular pressure. Identifying genes that modify glaucoma associated phenotypes is likely to provide insights to mechanisms of glaucoma. We previously reported glaucoma in DBA/2J mice caused by recessive alleles at two loci, isa and ipd, that cause iris stromal atrophy and iris pigment dispersion, respectively. A approach for identifying modifier genes is to study the effects of specific mutations in different mouse strains. When the phenotypic effect of a mutation is modified upon its introduction into a new strain, crosses between the parental strains can be used to identify modifier genes. The purpose of this study was to determine if the effects of the DBA/2J derived isa and ipd loci are modified in strain AKXD-28/Ty. 相似文献134.
Purification and partial characterisation of beet mild yellowing virus and its serological detection in plants and aphids 总被引:4,自引:0,他引:4
D. A. GOVIER 《The Annals of applied biology》1985,107(3):439-447
Beet mild yellowing virus (BMW) was reversibly precipitated at temperatures below about 5°C and this property was used as a final step in a purification procedure which yielded about 1 mg virus/kg tissue. Purified virus was infective and had an A200/A280 ratio of about 1–8. BMW particles were isometric with a diameter of 26 nm, sedimented at 116 S, had a buoyant density in caesium chloride of 1.42 g/cm3 and a coat protein mol. wt of 25 400. An antiserum to BMW had a titre in immunodiffusion tests of 1/256 and was used in immunodiffusion tests, immunospecific electron microscopy (ISEM) and enzyme-linked immunosorbent assay to demonstrate a close serological relationship between BMW and beet western yellows virus. BMW was readily detected by ISEM in plants and also in aphid vectors after treatment of aphid extracts with a chloroform:butanol mixture. 相似文献
135.
HEMIPARASITIC NUTRITION IN ANGIOSPERMS 总被引:2,自引:0,他引:2
136.
Z. G. XU A. J. COCKBAIN † R. D. WOODS D. A. GOVIER 《The Annals of applied biology》1988,113(2):287-296
An isolate (N15) of broad bean wilt virus (BB W V) from faba bean in China was compared with some other isolates and strains including the nasturtium ringspot strain (NRSV, BBWV serotype I), parsley virus 3 (PV3, serotype I) and BBWV isolate PV131 (serotype II). In host range studies, N15 infected 12 of 14 species, including soybean and spinach. It was purified from Chenopodium quinoa and pea by a method that yielded up to 8mg/100g tissue. By the same method, NRSV yielded up to 4mg/100 g. Purified preparations of N15 and NRSV contained isometric particles c. 26 nm in diameter which sedimented as three components, N15 at 62, 93 and 117 S, and NRSV at 60, 91 and 116 S. In immunodiffusion tests using antisera to N15 and NRSV, N15 was distinguishable from NRSV but indistinguishable from PV131. In ISEM tests, many more particles of N15 and NRSV were trapped by homologous than by heterologous antiserum; in decoration tests, much antibody attached to homologous particles but none to heterologous particles. In DAS ELISA using N15 antiserum, N15 and six other Chinese faba bean or pea isolates, and a Chinese spinach isolate, were readily detected and were indistinguishable from each other and from PV131; unlike NRSV and PV3, none of the Chinese isolates, nor PV131, was detected using NRSV antiserum. These results indicate that the Chinese isolates belong to BBWV serotype II group. 相似文献
137.
The evolution of prokaryotic ferredoxins--with a general method correcting for unobserved substitutions in less branched lineages 总被引:7,自引:0,他引:7
Thirty-one bacterial type ferredoxins were examined by means of the
parsimony method for their phylogenetic implications. The results show
reasonable relationships in that photosynthetic, thermophilic, and
desulfovibrio groups are identifiable; but a number of interesting
anomalies occur. These include a methanogen sequence that clusters among
the desulfovibrios. There are several differences from the phylogeny of
Woese. At least two duplications producing paralogous genes are
demonstrated, plus the probable existence of two more. The partial internal
gene duplication that doubled the length of ferredoxin is confirmed by
showing that the probability of the two ancestrally reconstructed halves
possessing that much similarity by chance is 10(- 7). Howard and co-workers
proposed that the two halves of the Azotobacter vinelandii are reversed
relative to most other sequences. A phylogeny, drawn with the halves of the
azotobacter sequence (and its relatives) reversed produced a tree that had
only three less nucleotide substitutions than did the tree without their
halves reversed. This plus other evidence suggests that the significantly
greater similarity observed across rather than within the halves is more
likely the result of convergence.
相似文献
138.
Evolution of antibiotic resistance genes: the DNA sequence of a kanamycin resistance gene from Staphylococcus aureus 总被引:14,自引:0,他引:14
The kanamycin resistance gene from Staphylococcus aureus has been sequenced
and its structure compared with similar genes isolated from Streptomyces
fradiae and from two transposons, Tn5 and Tn903, originally isolated from
Klebsiella pneumoniae and Salmonella typhimurium, respectively. The genes
are all homologous but, since their common ancestor, have undergone
extensive divergence, with more than 43% divergence between the closest
pair. The phylogeny of the genes cannot be made congruent to the phylogeny
of the taxa from which they were isolated without requiring rather
improbable differences in rates. One is therefore led to conclude that
there have been multiple occurrences of gene transfer between these
species. Thus, although they are homologous, they are neither orthologous
nor paralogous. It is suggested that homologous genes of this type be
called xenologous.
相似文献
139.
Olga V Savinova Fumihiro Sugiyama Janice E Martin Stanislav I Tomarev Beverly J Paigen Richard S Smith Simon WM John 《BMC genetics》2001,2(1):12-15
Background
Little is known about genetic factors affecting intraocular pressure (IOP) in mice and other mammals. The purpose of this study was to determine the IOPs of genetically distinct mouse strains, assess the effects of factors such as age, sex and time of day on IOP in specific strain backgrounds, and to assess the effects of specific candidate gene mutations on IOP. 相似文献140.
We examined annual variation in the timing of conception andparturition in the African buffalo (Syncerus caffer) and thesynchrony of birth timing with resource cues, using 8 yearsof monthly birth, rainfall, and vegetation data, measured asNormalized Difference Vegetation Index (NDVI). Monthly birthshad the strongest significant correlations with NDVI and rainfalllevels 12 and 13 months in the past, respectively. In addition,the synchrony of current year births corresponds most stronglyto the synchrony of the previous year's NDVI distribution. Becausethe gestation period of buffalo has been estimated to be around11 months, these findings suggest that improved protein levels,occurring approximately a month after the first green flushof the wet season, are either a trigger for conception or conceptionhas evolved to be synchronous with correlated environmentalcues that ensure females enter a period of peak body conditionaround the time of conception and/or parturition. With a gestationperiod of approximately 340 days, parturition occurs to takeadvantage of the period when forage has its highest proteincontent. A comparative analysis of gestation periods withinthe subfamily Bovinae indicates that African buffalo have aprotracted gestation for their body size, which we suggest isan adaptation to their seasonal environment. We also found thatinterannual variation in the birth distribution suggests a degreeof plasticity in the date of conception, and variation in thenumber of calves born each year suggest further synchrony ata timescale longer than a single year. 相似文献