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21.
本文介绍了两种预测DNA顺序上的启动子位置的计算机识别方法,方法1是基于启动子部位单核苷酸的分布不均一性,方法2是基于启动子部位二核苷酸的分布不均一性。分别用这两种方法推测了质粒pBR322DNA上启动子的位置,从而验证了化学实验的结果。 相似文献
22.
Knob heterochromatin homology in maize and its relatives 总被引:13,自引:0,他引:13
Summary We have characterised the major DNA sequence component of knob heterochromatin in maize, teosinte andTripsacum. Sequence analysis of this DNA gives strong support to the proposal that maize originated by selection of variants in teosinte. In situ hybridization has confirmed that this repeating DNA sequence, which is the major component of maize knob heterochromatin, is also the major component of knobs in teosinte,Zea diploperennis andTripsacum. In Southern blot hybridizations the repeat has a similar basic organization in all taxa;Tripsacum, however, is differentiated from maize and teosinte by a number of sequence features. Maize and teosinte knob heterochromatin are indistinguishable with regard to the distribution of mutations in the 180-bp repeat and the presence and organization of a 202-bp variant sequence. The knob DNA sequence was not detectable in three species ofCoix, an Old World genus of the Maydeae.Within the repeat unit is a 27-bp region that shows no sequence changes in maize, teosinte orTripsacum. The remainder of the repeat unit has randomly distributed nucleotide changes. The presence of the conserved sequence region suggests that knob DNA may have a functional role in the nucleus. 相似文献
23.
The genomes of phage I3 and its host Mycobacterium smegmatis have been compared. From thermal melting studies the GC contents of DNA from mycobacteriophage I3 and its host M. smegmatis were found to be 66%. A new method, based only on the initial rates of reassociation, has been developed for calculating the DNA homology. Analysis of DNA reassociation kinetics suggested the presence of one equivalent of the phage I3 genome within the M. smegmatis genome. Southern analysis revealed the presence of almost all of the phage I3 specific sequences within the host genome. 相似文献
24.
25.
Primary structure of a pheromone-binding protein from Antheraea pernyi: homologies with other ligand-carrying proteins 总被引:5,自引:0,他引:5
K. Raming J. Krieger H. Breer 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(5):503-509
Summary An antennal cDNA clone encoding the complete sequence (163 amino acids) of a pheromone-binding protein precursor from the male silk moth, Antheraea pernyi, was isolated using oligonucleotide probes. The cloned cDNA was expressed and the translation product detected by specific antibodies. The deduced protein sequence consists of a signal peptide of 21 amino acids and a mature binding protein of 142 amino acid residues. The predicted structure of this protein is homologous to binding-proteins from different insect species which have previously been identified, but shows no similarities to odorant-binding proteins from vertebrates, suggesting that soluble odorant-binding proteins in insects and vertebrates represent an evolutionary convergence.Abbreviations
PBP
pheromone-binding protein
-
OBP
odorant-binding protein
-
cDNA
complentary DNA
-
poly(A
+) RNA
polyadenylated RNA
-
SSC
0.15 M sodium chloride+0.015 M sodium citrate
-
SDS-PAGE
sodium dodecylsulfate polyacrylamide gelelectrophoresis 相似文献
26.
Martijn A. Huynen 《Journal of molecular evolution》1996,43(3):165-169
RNA secondary-structure folding algorithms predict the existence of connected networks of RNA sequences with identical secondary
structures. Fitness landscapes that are based on the mapping between RNA sequence and RNA secondary structure hence have many
neutral paths. A neutral walk on these fitness landscapes gives access to a virtually unlimited number of secondary structures
that are a single point mutation from the neutral path. This shows that neutral evolution explores phenotype space and can
play a role in adaptation.
Received: 23 December 1995 / Accepted: 17 March 1996 相似文献
27.
Manfred Tacker Peter F. Stadler Erich G. Bornberg-Bauer Ivo L. Hofacker P. Schuster 《European biophysics journal : EBJ》1996,25(2):115-130
Algorithms predicting RNA secondary structures based on different folding criteria – minimum free energies (mfe), kinetic
folding (kin), maximum matching (mm) – and different parameter sets are studied systematically. Two base pairing alphabets
were used: the binary GC and the natural four-letter AUGC alphabet. Computed structures and free energies depend strongly on both the algorithm and the parameter set. Statistical
properties, such as mean number of base pairs, mean numbers of stacks, mean loop sizes, etc., are much less sensitive to the
choice of parameter set and even of algorithm. Some features of RNA secondary structures, such as structure correlation functions,
shape space covering and neutral networks, seem to depend only on the base pairing logic (GC or AUGC alphabet).
Received: 16 May 1996 / Accepted: 10 July 1996 相似文献
28.
人分裂细胞核抗原基因片段的筛选、测序及对启动子的分析 总被引:1,自引:0,他引:1
经6.6×105个克隆筛选,从装在λ噬菌体载体Charon30中的人基因库中筛选到了一个含人分裂细胞核抗原(PCNA)基因的克隆。经Southern杂交分析插入基因长约14kb,有较长的5'上游区,但3'端缺少一部分。经亚克隆和测序已确定从5'上游1263bp到3'端与λ载体接点共4969bpPCNA基因片段的核苷酸序列。将PCNA基因启动子核苷酸序列与DNA聚合酶α,拓扑异构酶Ⅱα,胸苷酸激酶基因的启动子进行比较有30%以上同源性,具有“看家基因”特征。在转录起始点的5'上游几百bp的范围内都有与CAT,SP1,E2F,NFHB,Oct1和ATF等转录因子的结合位点相似的核苷酸序列。 相似文献
29.
Summary The Upper Santonian to Lower CampanianLacazina Limestone consists of massive, often amalgamated beds of packstones and grainstones which were deposited in a shallow marine
environment. The most abundant skeletal components are miliolid foraminifera, echinoderm, bivalve and bryozoan fragments,
peloids and sparse red algae. Small, solitary corals only occur sporadically. Hermatypic corals, sponges and green algae are
missing. The series which reaches thicknesses between 60 m and 160 m, was sampled at intervals of 0.5 m at five localities.
The petrographic features throughout the series are mainly a product of changing depositional energy. The limestones are well
cemented. Diagenesis is characterized by a transition from marine phreatic to burial cementation. Syntaxial and blocky calcite
cements predominate over early acicular to bladed and microgranular cements.
The faunal association within theLacazina Limestone exhibits features typical for temperate water i.e.foramol carbonates. On the other hand, oxygen (δ18O =-1.7 to −6.3 ‰ PDB) and carbon (δ13C to 3.0‰ PDB) isotope values of diagentically unaltered bivalve shells indicate warm surface waters corresponding better
to the palaeogeographical situation of theLacazina Limestone. Nutrient-surplus is proposed as a limiting factor preventing the development of reefs and finally ofchlorozoan sediments.
In the sense of sequence stratigraphy, theLacazina Limestone is interpreted to contain transgressive and highstand systems tracts. This interpretation fits well into theHaq-Vail-curve. The series shows no visible high-frequency cyclicity in the field. Several cycles were found by means of principle
component analysis and spectral analysis. Their relationships to the Milankovitch spectrum are discussed.
The ammonite fauna of the unit and of preceding sediments (late Coniacian to early Campanian) is described and some inoceramids
are figured. They permit—for the first time—the exact dating of theLacazina Limestone in the Basco-Cantabrian Basin (BCB) and throw light on a prominent faunal change at the Coniacian/Santonian boundary.
The Cenomanian to Coniacian ammonite faunas which were dominated by endemic Tethyan pseudoceratitic faunas are replaced by
cosmopolitan species dominated by Madagascan elements. This drastic change permits speculations about the installation of
a new oceanic current system in the Santonian. 相似文献
30.
Michael A. Rogers Jürgen Schweizer Thomas Krieg Hermelita Winter 《Molecular biology reports》1994,20(3):155-161
We present the nucleotide and amino acid sequence for a novel human type I hair keratin, which could be identified through its high sequence homology and strict carboxyterminal length identity as a human ortholog of the murine hair keratin mHa3. Our hHa3 sequence differs, however, from that of a previously described hHa3 hair keratin (published only as an amino acid sequence; [13]) in 24 amino acid positions, 8 of which occur in the middle of the carboxyterminal domain. PCR of genomic DNA from 25 normal human subjects using a primer pair derived from sequence segments located in the 3-region of our hHa3 clone that encode conserved amino acid sequences in both keratins, resulted in the amplification of two distinct products of 0.38 kbp and 1.0 kbp. DNA sequence analysis of the cloned PCR products allowed identification of the 0.38 kb sequence as that originating from Yuet al. [13] and the 1.0 kb sequence as that being derived from our data. The difference in fragment length was due to unique intron 6 sequences, indicating that these two keratin species are encoded by genes of their own. Moreover, extensive Southern blot analyses with DNA from 25 unrelated individuals of different races using a 3-noncoding sequence from our keratin and the intron 6 sequence of the keratin of Yuet al. [13], as hybridization probes showed that both keratin genes are present as single copy sequences occurring ubiquitously and without gross alterations in the human genome. Collectively, these data demonstrate that the human type I hair keratin described in this paper represents an isoform of the previously described hHa3 keratin. We propose that these hHa3 isoforms be named in chronological order of discovery hHa3-I and hHa3-II. 相似文献