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Selection is the major force affecting local levels of genetic variation in species. The availability of dense marker maps offers new opportunities for a detailed understanding of genetic diversity distribution across the animal genome. Over the last 50 years, cattle breeds have been subjected to intense artificial selection. Consequently, regions controlling traits of economic importance are expected to exhibit selection signatures. The fixation index (Fst) is an estimate of population differentiation, based on genetic polymorphism data, and it is calculated using the relationship between inbreeding and heterozygosity. In the present study, locally weighted scatterplot smoothing (LOWESS) regression and a control chart approach were used to investigate selection signatures in two cattle breeds with different production aptitudes (dairy and beef). Fst was calculated for 42 514 SNP marker loci distributed across the genome in 749 Italian Brown and 364 Piedmontese bulls. The statistical significance of Fst values was assessed using a control chart. The LOWESS technique was efficient in removing noise from the raw data and was able to highlight selection signatures in chromosomes known to harbour genes affecting dairy and beef traits. Examples include the peaks detected for BTA2 in the region where the myostatin gene is located and for BTA6 in the region harbouring the ABCG2 locus. Moreover, several loci not previously reported in cattle studies were detected.  相似文献   
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Summary Segments of the TL-DNA of the agropine type Ri plasmid pRi 1855 encompassing single and groups of open-reading frames were cloned in the Ti plasmid-derived binary vector system Bin 19. Leaf disc infections on Nicotiana tabacum led to transformed plants, some of which showed typical hairy root phenotypes, such as the wrinkled leaf morphology, excessive and partially non geotropic root systems and the ability of leaf explants to differentiate roots in a hormone-free culture medium. Particularly interestingly, most of these traits were shown by plants transformed with a TL-DNA segment encompassing the single ORF 11, corresponding to the rolB locus. Hairy root can be induced by this latter T-DNA segment on wounded stems of tobacco plants; hairy root induction on carrot discs requires, on the contrary, a more complex complement of TL-DNA genes.Abbreviations YMB yeast mannitol broth - MS Murashige and Skoog medium - 6-BAP 6-benzylaminopurine - NAA naphthalene acetic acid - Km kanamycin - Cb carbenicillin  相似文献   
4.
Molecular heterogeneity underlying the G6PD Mediterranean phenotype   总被引:4,自引:0,他引:4  
Summary As part of a study aiming to define the molecular basis of glucose-6-phosphate dehydrogenase (G6PD) deficiency, we analysed a sample from a Portugese boy with a family history of favism. Although the biochemical properties of red-cell G6PD from this subject were similar to those of the common variant G6PD Mediterranean, the corresponding mutation (563 CT) was not present. Instead, polymerase chain reaction (PCR) amplification and sequencing of the entire gene detected a CT transition at nucleotide 592 in exon VI, changing an arginine residue to a cysteine residue only 10 amino acids downstream from the Mediterranean mutation. Single-strand conformation polymorphism analysis of a PCR-amplified DNA fragment spanning exons VI and VII of the G6PD gene has detected the same mutation, confirmed by sequencing, in a G6PD-deficient patient from Southern Italy. We name this new variant G6PD Coimbra.  相似文献   
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Summary The oxygen binding of whole blood from humans and two arctic mammals, reindeer and muskox, has been studied as a function of carbon dioxide and temperature. All bloods display a marked Bohr effect with Bohr coefficients in the range –0.44––0.73. The Bohr effect is more pronounced at 20°C. The temperature sensitivity of reindeer and muskox blood expressed by the apparent heat of oxygenation, H, is almost three times lower than that of human HbA under the same experimental conditions. This thermodynamic difference gives special benefits to arctic mammals with large heterothermy by safeguarding oxygen unloading at very low ambient temperatures.  相似文献   
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A stochastic model for cooperative transitions in biological systems based on a Markov chain is proposed. This model requires only two parameters, the mean probability, p, and the coupling capacity, Deltap, which measure the probability of forming a new weak bond depending on the number of similar bonds already formed and it is also responsible for the transition. In this paper we show how the model works for a large number of identical molecules and how it can be useful for studying the noise around the centre of the transition where, increasing the degree of cooperativity, i.e. the number n in the well-known Hill equation, the width of the noise increases along with its fractal dimension. A simple relationship between the degree of cooperativity and the parameter Deltap is proposed, suggesting that the cooperativity of real biological transitions is related to the coupling capacity Deltap of the present model.  相似文献   
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-Hexosaminidase gene mutations were analyzed in two adult-onset Sandhoff disease Italian patients by PCR analysis of a common known mutation (5) and by heteroduplex analysis of genomic and RT-PCR DNA fragments, covering the whole gene. The patients' genotypes were 5/C1214T, and G890A/C1214T, respectively. As mutation C1214T (Pro405Leu) is also present in the other two late-onset cases so far described, we suggest that C1214T is a common mutation in this type of Sandhoff disease. Mutation G890A (Cys297Tyr) is a novel mutation which presumably causes altered processing of the pro chain.  相似文献   
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The objective of this study was to determine whether cells in G(0) phase are functionally distinct from those in G(1) with regard to their ability to respond to the inducers of DNA synthesis and to retard the cell cycle traverse of the G(2) component after fusion. Synchronized populations of HeLa cells in G(1) and human diploid fibroblasts in G(1) and G(0) phases were separately fused using UV-inactivated Sendai virus with HeLa cells prelabeled with [(3)H]ThdR and synchronized in S or G(2) phases. The kinetics of initiation of DNA synthesis in the nuclei of G(0) and G(1) cells residing in G(0)/S and G(1)/S dikaryons, respectively, were studied as a function of time after fusion. In the G(0)/G(2) and G(1)/G(2) fusions, the rate of entry into mitosis of the heterophasic binucleate cells was monitored in the presence of Colcemid. The effects of protein synthesis inhibition in the G(1) cells, and the UV irradiation of G(0) cells before fusion, on the rate of entry of the G(2) component into mitosis were also studied. The results of this study indicate that DNA synthesis can be induced in G(0)nuclei after fusion between G(0)- and S-phase cells, but G(0) nuclei are much slower than G(1) nuclei in responding to the inducers of DNA synthesis because the chromatin of G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells differ from G(1) cells with regard to their effects on the cell cycle progression of the G(2) nucleus into mitosis. This difference between G(0) and G(1) cells appears to depend on certain factors, probably nonhistone proteins, present in G(1) cells but absent in G(0) cells. These factors can be induced in G(0) cells by UV irradiation and inhibited in G(1) cells by cycloheximide treatment.  相似文献   
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