Intron a

Câu 1: Giả sử một mARN được cấu tạo từ 3 loại nuclêôtit: A, U, G thì trên mạch gốc của gen này có thể có tối đa bao nhiêu loại mã bộ ba? A. 6 loại mã bộ ba. B. 3 loại mã bộ ba. C. 27 loại mã bộ ba. D. 9 loại mã bộ ba. Câu 2: Ở sinh vật nhân thực, trình tự nuclêôtit trong vùng mã hóa của gen nhưng không mã hóa axit amin được gọi là A. đoạn intron. B. đoạn êxôn. C. gen phân mảnh. D. vùng vận hành. Câu...

64p huyentrangho 20-05-2013 284 71   Download

The two group I introns Nae.L1926 and Nmo.L2563, found at two different sites in nuclear LSU rRNA genes of Naegleria amoebo-flagellates, have been characterized in vitro. Their structural organization is related to that of the mobile Physarum intron Ppo.L1925 (PpLSU3) with ORFs extending the L1-loop of a typical group IC1 ribozyme. Nae.L1926, Nmo.L2563 and Ppo.L1925 RNAs all selfsplice in vitro, generating ligated exons and full-length intron circles as well as internal processed excised intron RNAs....

9p system191 01-06-2013 29 5   Download

The case of homologous monomeric c-type and oligomeric b-type crystallins has been described and analyzed in evolutionary terms. Data and hypotheses from molecular genetics and structural investigations converge and suggest a novel three-phase model for the evolutionary history of crystallin-type proteins. In the divergent cascades of monomeric and oligomeric crystallins, a pivotal role was played by alterations in the gene segments encoding the C-terminal extensions and the intermotif or interdomain linker peptides.

9p system191 01-06-2013 45 4   Download

We report here the full coding sequence of a novel mouse putative membrane-associated mucin containing three extracellular EGF-like motifs and a mucin-like domain consisting of at least 20 tandem repeats of 124–126 amino acids. Screening a cosmid and a BAC libraries allowed to isolate several genomic clones. Genomic and cDNA sequence comparisons showed that the gene consists of 25 exons and 24 introns covering a genomic region of  52 kb. The first intron is  16 kb in length and is followed by an unusually large exon ( 9.5 kb) encoding Ser/Thr-rich tandemly repeated sequences....

10p system191 01-06-2013 47 4   Download

Manganese lipoxygenase was isolated to homogeneity from the take-all fungus, Gaeumannomyces graminis. The C-terminal amino acids and several internal peptides were sequenced, and the information was used to obtain a cDNA probe by RT/PCR. Screening of a genomic library of G. graminis yielded a full-length clone of the Mn-Lipoxygenase gene. cDNA analysis showed that the gene spanned 2.6 kb and contained one intron (133 bp). Northern blot analyses indicated two transcripts (2.7 and 3.1 kb). The deduced amino-acid sequence of the Mn-Lipoxygenase precursor (618 amino acids, 67.

8p system191 01-06-2013 39 4   Download

We report the cloning and functional charaterization of the full-length cDNA and gene encoding a Toxoplasma gondii DNA repair enzyme designated TgDRE. The gene is composed of three exons separated by two introns of 780 and 630 bp, and encodes a protein with a predicted molecular mass of 49.6 kDa. The native TgDRE protein, with a molecular mass of 60 kDa, is only detected in the virulent tachyzoite stage of T. gondii. However, the transcript is present in both asexual parasite stages, virulent tachyzoite and avirulent encysted bradyzoite. ...

9p research12 01-06-2013 37 5   Download

Murine pregnancy-associated plasma protein-A (PAPP-A) cDNA encoding a 1545 amino-acid protein has been cloned. We have also identified and cloned cDNA that encodes a novel variant of PAPP-A, PAPP-Ai, carrying a 29-residue highly basic insert. The point of insertion corresponds to a junction between two exons in the human PAPP-A gene. The human intron flanked by these exons does not encode a homologous corresponding insert, which is unique to the mouse.

10p research12 01-06-2013 44 6   Download

We have characterized a glycosylated, 31 amino-acid peptide of 4932 Da isolated from Drosophila melanogaster males. The mature peptide contains a sugar moiety of 1184 Da at a NDT consensus glycosylation site and a disulfide bond. It is synthesized in the male ejaculatory duct via a 54 amino-acid precursor containing an N-terminal signal peptide and Arg-Lys at the C-terminus which is cleaved off during maturation. The gene contains an intron of 53 bp and is localized in the cytological region 99B of the D. melanogaster genome....

9p research12 01-06-2013 41 4   Download

The freeze-intolerant insect, Choristoneura fumiferana (spruce budworm), produces multiple antifreeze protein (AFP) isoforms for protection during the overwintering stage.We nowreport the cloning ofAFPgenes frominsects; Afp-Lu1encodes a 9-kDa AFP isoform, andAfp-Iu1 encodes a12-kDa AFP isoform. BothCfAFP genes have similar structures with a single 3- to 3.6-kb intron inter-rupting the coding region.

9p research12 29-04-2013 34 3   Download

Froma cDNA library of Chinese scorpionButhus martensii Karsch, full-length cDNAs of 351 nucleotides encoding precursors (named BmKIM) that contain signal peptides of 21 amino acid residues, a mature toxin of 61 residues with four disulfide bridges, and an extra Gly-Lys-Lys tail, were isolated. The genomic sequence of BmKIM was cloned and sequenced; it consisted of two exons disrupted by an intron of 1622 bp, the largest known in scorpion toxin genomes, inserted in the region encoding the signal peptide. The cDNA was expressed inEscherichia coli....

8p research12 23-04-2013 38 2   Download

In humans, thromboxane (TX) A2 signals through two TXA2receptor (TP) isoforms, TPaand TPb,thatdiverge within their carboxyl terminal cytoplasmic (C) tail regions and arise by differential splicing. The human TP gene con-tains three exons E1–E3; while E1 exclusively encodes 5¢ untranslatedregion (UTR) sequence,E2andE3 represent the main coding exons. An additional noncoding exon, E1b was identified within intron 1. Additionally, the TP gene contains twopromoters P1 andP2 located 5¢of E1 andE1b, respectively....

16p research12 23-04-2013 44 3   Download

The complete coding sequence of a BDIX rat gene homo-logous to the human ABO gene was determined. Identifi-cation of the exon–intron boundaries, obtained by comparison of the coding sequence with rat genomic sequences from data banks, revealed that the rat gene structure is identical to that of the human ABO gene. It localizes to rat chromosome 3 (q11-q12), a region homolo-gous to human 9q34.

8p research12 23-04-2013 41 3   Download

The cystic ®brosis transmembrane conductance regulator (CFTR) gene shows a complex pattern of expression, with temporal and spatial regulation that is not accounted for by elements in the promoter. One approach to identifying the regulatory elements forCFTRis the mapping of DNase I hypersensitive sites (DHS) within the locus. We previously identi®ed at least 12 clusters of DHS across theCFTRgene andhere further evaluateDHS in introns 2, 3, 10, 16, 17a, 18, 20 and 21 to assess their functional importance in regulation ofCFTRgene expression. ...

7p research12 23-04-2013 32 2   Download

The AnCOB group I intron fromAspergillus nidulans encodes a homing DNA endonuclease called I-AniI which also functions as a maturase, assisting in AnCOB intron RNA splicing. In this investigation we biochemically char-acterized the endonuclease activity of I-AniIin vitro and utilizedcompetitionassays toprobe the relationshipbetween theRNA- andDNA-binding sites.

12p tumor12 20-04-2013 35 3   Download

Thebrain fattyacid-bindingprotein (B-FABP) is involved in brain development and adult neurogenesis. We have deter-mined the sequence of the gene encoding the B-FABP in zebrafish. The zebrafish B-FABP gene spans 2370 bp and contains four exons interruptedby three introns. The coding sequence of zebrafishB-FABP gene is identical to its cDNA sequence and the coding capacity of each exon is the same as that for the human and mouse B-FABP genes. A 1249 bp sequence 5¢ upstream of exon 1 of the zebrafish B-FABP gene was cloned and sequenced. ...

11p tumor12 20-04-2013 56 2   Download

Synaptophysin, one of the major proteins on synaptic vesi-cles, is ubiquitously expressed throughout the brain. Syn-aptophysin and synapsin I, another synaptic vesicle protein, are also expressed by retinoic acid-induced neuronally dif-ferentiated P19 teratocarcinoma cells. Here, we show that inhibition of histone deacetylase activity in P19 cells is suf-ficient to activate transcription of the synaptophysin and synapsin I genes, indicating that neuronal differentiation and impairment of histone deacetylases results in a similar gene expression pattern....

8p tumor12 20-04-2013 31 2   Download

Glucose transporters (GLUTs) have been implicated in adaptive and survival responses to hypoxic stress in mam-mals. In fish, the expression and regulation ofGLUT in relation to hypoxia remains unexplored. Here we describe the identification ofa hypoxia-responsive glucose transpor-ter gene (gcGLUT) and the corresponding full-length cDNA from the grass carp. The gene spans
11 kb ofgenomic sequence and consists of12 exons and 11 introns, and an open reading frame (ORF) of 1599 bp encoding a poly-peptide of533 amino acids, with a predictedmolecularmass of
57 kDa and a pI of8.34....

8p fptmusic 16-04-2013 42 3   Download

We have isolated a cDNA that encodes a novel serine protease, prosemin, from human brain. The cDNA of human prosemin is 1306 bp, encoding 317 amino acids. It showed significant homology with the sequence of a chromosome 16 cosmid clone (accession no. NT_037887.4). The prosemin gene contains six exons and five introns. The amino acid sequence of prose-min shows significant homology to prostasin,c-tryptase, and testisin (43%, 41%, and 38% identity, respectively), the genes of which are also located on chromosome 16. ...

13p fptmusic 12-04-2013 30 4   Download

Group I introns are thought to be self-propagating mobile elements, and are distributed over a wide range of organisms through horizontal trans-mission. Intron invasion is initiated through cleavage of a target DNA by a homing endonuclease encoded in an open reading frame (ORF) found within the intron. The intron is likely of no benefit to the host cell and is not maintained over time, leading to the accumulation of mutations after intron invasion.

0p awards 06-04-2013 44 2   Download

We used a combined computer and biochemical approach to characterize human pyridoxine 5¢-phosphate oxidase (PNPO).The human PNPOgene is composed of seven exons and six introns, and spans approximately 8 kb.All exon/intron junctions contain the gt/ag consensus splicing site.The absence of TATA-like sequences, the presence of Sp1-binding sites and more importantly, the presence of CpG islands in the regulatory region of thePNPOgene are characteristic features of housekeeping genes.

10p dell39 03-04-2013 48 3   Download