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1.
2.
The Habbani Yemeni Jews were a religious isolate in Yemen for centuries. Since a bottleneck in the late eighteenth century the population, composed of six partrilineages, has steadily grown. Isonymy analysis of Habbani genealogies reveals a significant increase in lineage endogamy by the early twentieth century, suggesting that microdifferentiation of Habbani population genetic structure along the patrilineages was occurring. We examine reflectance data from a "parental" generation of 159 individuals studied by Hulse in the 1960s and reflectance data from an "offspring" generation of 243 individuals studied by Towne in the 1980s. A greater amount of interlineage skin color differences is found in the offspring generation than in the parental generation. This finding is consistent with what is known of the evolution of Habbani population genetic structure. 相似文献
3.
DNA sequences were determined for three to five alleles of the bride-of-
sevenless (boss) gene in each of four species of Drosophila. The product of
boss is a transmembrane receptor for a ligand coded by the sevenless gene
that triggers differentiation of the R7 photoreceptor cell in the compound
eye. Population parameters affecting the rate and pattern of molecular
evolution of boss were estimated from the multinomial configurations of
nucleotide polymorphisms of synonymous codons. The time of divergence
between D. melanogaster and D. simulans was estimated as approximately 1
Myr, that between D. teissieri and D. yakuba as approximately 0.75 Myr, and
that between the two pairs of sibling species as approximately 2 Myr. (The
boss genes themselves have estimated divergence times approximately 50%
greater than the species divergence times.) The effective size of the
species was estimated as approximately 5 x 10(6), and the average mutation
rate was estimated as 1-2 x 10(-9)/nucleotide/generation. The ratio of
amino acid polymorphisms within species to fixed differences between
species suggests that approximately 25% of all possible single-step amino
acid replacements in the boss gene product may be selectively neutral or
nearly neutral. The data also imply that random genetic drift has been
responsible for virtually all of the observed differences in the portion of
the boss gene analyzed among the four species.
相似文献
4.
High rate of DNA loss in the Drosophila melanogaster and Drosophila virilis species groups 总被引:3,自引:3,他引:3
We recently proposed that patterns of evolution of non-LTR
retrotransposable elements can be used to study patterns of spontaneous
mutation. Transposition of non-LTR retrotransposable elements commonly
results in creation of 5' truncated, "dead-on-arrival" copies. These
inactive copies are effectively pseudogenes and, according to the neutral
theory, their molecular evolution ought to reflect rates and patterns of
spontaneous mutation. Maximum parsimony can be used to separate the
evolution of active lineages of a non-LTR element from the fate of the
"dead-on-arrival" insertions and to directly assess the relative
frequencies of different types of spontaneous mutations. We applied this
approach using a non-LTR element, Helena, in the Drosophila virilis group
and have demonstrated a surprisingly high incidence of large deletions and
the virtual absence of insertions. Based on these results, we suggested
that Drosophila in general may exhibit a high rate of spontaneous large
deletions and have hypothesized that such a high rate of DNA loss may help
to explain the puzzling dearth of bona fide pseudogenes in Drosophila. We
also speculated that variation in the rate of spontaneous deletion may
contribute to the divergence of genome size in different taxa by affecting
the amount of superfluous "junk" DNA such as, for example, pseudogenes or
long introns. In this paper, we extend our analysis to the D. melanogaster
subgroup, which last shared a common ancestor with the D. virilis group
approximately 40 MYA. In a different region of the same transposable
element, Helena, we demonstrate that inactive copies accumulate deletions
in species of the D. melanogaster subgroup at a rate very similar to that
of the D. virilis group. These results strongly suggest that the high rate
of DNA loss is a general feature of Drosophila and not a peculiar property
of a particular stretch of DNA in a particular species group.
相似文献
5.
Srabani Bhaumik Jean Boyer Chaitali Banerjee Samantha Clark Noemi Sebastiao Elizabeth Vela Penny Towne 《Journal of cellular biochemistry》2020,121(12):4974-4990
In preclinical cancer studies, three-dimensional (3D) cell spheroids and aggregates are preferred over monolayer cell cultures due to their architectural and functional similarity to solid tumors. We performed a proof-of-concept study to generate physiologically relevant and predictive preclinical models using non–small cell lung adenocarcinoma, and colon and colorectal adenocarcinoma cell line-derived 3D spheroids and aggregates. Distinct panels were designed to determine the expression profiles of frequently studied biomarkers of the two cancer subtypes. The lung adenocarcinoma panel included ALK, EGFR, TTF-1, and CK7 biomarkers, and the colon and colorectal adenocarcinoma panel included BRAF V600E, MSH2, MSH6, and CK20. Recent advances in immunofluorescence (IF) multiplexing and imaging technology enable simultaneous detection and quantification of multiple biomarkers on a single slide. In this study, we performed IF staining of multiple biomarkers per section on formalin-fixed paraffin-embedded 3D spheroids and aggregates. We optimized protocol parameters for automated IF and demonstrated staining concordance with automated chromogenic immunohistochemistry performed with validated protocols. Next, post-acquisition spectral unmixing of the captured fluorescent signals were utilized to delineate four differently stained biomarkers within a single multiplex IF image, followed by automated quantification of the expressed markers. This workflow has the potential to be adapted to preclinical high-throughput screening and drug efficacy studies utilizing 3D spheroids from cancer cell lines and patient-derived organoids. The process allows for cost, time, and resource savings through concurrent staining of several biomarkers on a single slide, the ability to study the interactions of multiple expressed proteins within a single region of interest, and enable quantitative assessment of biomarkers in cancer cells. 相似文献
6.
The contractile basis of amoeboid movement: V. The control of gelation, solation, and contraction in extracts from dictyostelium discoideum 总被引:7,自引:22,他引:7 下载免费PDF全文
Motile extracts have been prepared from Dictyostelium discoideum by homogenization and differential centrifugation at 4 degrees C in a stabilization solution (60). These extracts gelled on warming to 25 degrees Celsius and contracted in response to micromolar Ca++ or a pH in excess of 7.0. Optimal gelation occurred in a solution containing 2.5 mM ethylene glycol-bis (β-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA), 2.5 mM piperazine-N-N'-bis [2-ethane sulfonic acid] (PIPES), 1 mM MgC1(2), 1 mM ATP, and 20 mM KCI at ph 7.0 (relaxation solution), while micromolar levels of Ca++ inhibited gelation. Conditions that solated the gel elicited contraction of extracts containing myosin. This was true regardless of whether chemical (micromolar Ca++, pH >7.0, cytochalasin B, elevated concentrations of KCI, MgC1(2), and sucrose) or physical (pressure, mechanical stress, and cold) means were used to induce solation. Myosin was definitely required for contraction. During Ca++-or pH-elicited contraction: (a) actin, myosin, and a 95,000-dalton polypeptide were concentrated in the contracted extract; (b) the gelation activity was recovered in the material sqeezed out the contracting extract;(c) electron microscopy demonstrated that the number of free, recognizable F-actin filaments increased; (d) the actomyosin MgATPase activity was stimulated by 4- to 10-fold. In the absense of myosin the Dictyostelium extract did not contract, while gelation proceeded normally. During solation of the gel in the absense of myosin: (a) electron microscopy demonstrated that the number of free, recognizable F- actin filaments increased; (b) solation-dependent contraction of the extract and the Ca++-stimulated MgATPase activity were reconstituted by adding puried Dictyostelium myosin. Actin purified from the Dictyostelium extract did not gel (at 2 mg/ml), while low concentrations of actin (0.7-2 mg/ml) that contained several contaminating components underwent rapid Ca++ regulated gelation. These results indicated : (a) gelation in Dictyostelium extracts involves a specific Ca++-sensitive interaction between actin and several other components; (b) myosin is an absolute requirement for contraction of the extract; (c) actin-myosin interactions capable of producing force for movement are prevented in the gel, while solation of the gel by either physical or chemical means results in the release of F-actin capable of interaction with myosin and subsequent contraction. The effectiveness of physical agents in producting contraction suggests that the regulation of contraction by the gel is structural in nature. 相似文献
7.
The highly sensitive, convenient fluorescence assay, based on the oxidation of nonfluorescent 10-acetyl-3,7-dihydroxyphenoxazine (Amplex Red) to highly fluorescent resorufin, is becoming increasingly popular for hydrogen peroxide quantitation. Yet, the intricacies of the horseradish peroxidase-catalyzed oxidation of the reductant substrate Amplex Red by hydrogen peroxide and the resulting resorufin could complicate the assay design and data interpretation. In particular, substrate inhibition and enzyme inactivation at higher hydrogen peroxide concentrations were known to affect the enzyme kinetics and end-point fluorescence. In addition, here we report the spontaneous transformation of resorufin to less or nonfluorescent product(s) in the absence of hydrogen peroxide and horseradish peroxidase. This spontaneous decay of resorufin fluorescence is most prominent in the pH range 6.2-7.7, likely due to general base-catalyzed de-N-acetylation and polymerization of resorufin. From a practical point of view, precautions for properly designing assays for hydrogen peroxide or characterizing hydrogen peroxide-generating systems are discussed based on the spontaneous transformation of resorufin to less fluorescent compound(s), substrate inhibition and enzyme inactivation at higher (>100 microM) hydrogen peroxide concentrations, and enzymatic oxidation of resorufin to nonfluorescent resazurin. 相似文献
8.
9.
In the Kansas Flint Hills, grassland burning is conducted during a relatively narrow window because management recommendations for the past 40 years have been to burn only in late spring. Widespread prescribed burning within this restricted time frame frequently creates smoke management issues downwind. A potential remedy for the concentrated smoke production in late spring is to expand burning to times earlier in the year. Yet, previous research suggested that burning in winter or early spring reduces plant productivity and cattle weight gain while increasing the proportion of undesirable plant species. In order to better understand the ecological consequences of burning at different times of the year, plant production and species abundance were measured for 20 years on ungrazed watersheds burned annually in autumn, winter, or spring. We found that there were no significant differences in total grass production among the burns on either upland or lowland topographic positions, although spring burned watersheds had higher grass culm production and lower forb biomass than autumn and winter burned watersheds. Burning in autumn or winter broadened the window of grass productivity response to precipitation, which reduces susceptibility to mid-season drought. Burning in autumn or winter also increased the phenological range of species by promoting cool-season graminoids without a concomitant decrease in warm-season grasses, potentially widening the seasonal window of high-quality forage. Incorporating autumn and winter burns into the overall portfolio of tallgrass prairie management should increase the flexibility in managing grasslands, promote biodiversity, and minimize air quality issues caused by en masse late-spring burning with little negative consequences for cattle production. 相似文献
10.
Anja Derer Bettina Groetsch Ulrike Harre Christina B?hm Jennifer Towne Georg Schett Silke Frey Axel J. Hueber 《PloS one》2014,9(8)