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1.
The metaphor of the “genetic program,” indicating the genome as a set of instructions required to build a phenotype, has been very influential in biology despite various criticisms over the years. This metaphor, first published in 1961, is thought to have been invented independently in two different articles, one by Ernst Mayr and the other by François Jacob and Jacques Monod. Here, after a detailed analysis of what both parties meant by “genetic program,” I show, using unpublished archives, the strong resemblance between the ideas of Mayr and Monod and suggest that their idea of genetic program probably shares a common origin. I explore the possibility that the two men met before 1961 and also exchanged their ideas through common friends and colleagues in the field of molecular biology. Based on unpublished correspondence of Jacob and Monod, I highlight the important events that influenced the preparation of their influential paper, which introduced the concept of the genetic program. Finally, I suggest that the genetic program metaphor may have preceded both papers and that it was probably used informally before 1961.  相似文献   

2.
The metaphor of the adaptive landscape, introduced by Sewall Wright in 1932, has played, and continues to play, a central role in much evolutionary thought. I argue that the use of this metaphor is tied to a teleological view of the evolutionary process, in which natural selection directs evolution toward an improved future state. I argue further that the use of “relative fitnesses” standardized to an arbitrary value, which is closely connected with the metaphor of an adaptive landscape, produces a disconnect between the mean fitness of a population and any real property of that population. This allows for a vague and ill-defined improvement to occur under the influence of selection. Instead, I suggest that relative fitnesses should be standardized by the mean absolute fitness (expected population growth rate), so that they express the expected rate of increase in frequency, rather than number. Under this definition, the mean relative fitness of all populations is always 1.0, and never changes as long as the population continues to exist.  相似文献   

3.
DNA sequence representation without degeneracy   总被引:2,自引:0,他引:2       下载免费PDF全文
Yau SS  Wang J  Niknejad A  Lu C  Jin N  Ho YK 《Nucleic acids research》2003,31(12):3078-3080
Graphical representation of DNA sequence provides a simple way of viewing, sorting and comparing various gene structures. A new two-dimensional graphical representation method using a two- quadrant Cartesian coordinates system has been derived for mathematical denotation of DNA sequence. The two-dimensional graphic representation resolves sequences’ degeneracy and is mathematically proven to eliminate circuit formation. Given x-projection and y-projection of any point on the graphical representation, the number of A, G, C and T from the beginning of the sequence to that point could be found. Compared with previous methods, this graphical representation is more in-line with the conventional recognition of linear sequences by molecular biologists, and also provides a metaphor in two dimensions for local and global DNA sequence comparison.  相似文献   

4.
Bert O. States 《Dreaming》1998,8(4):223-228
My response to Allan Hobson makes several points. Primarily, I argue that the coherence of any dream cannot be determined by the recall of the dream events alone. Rather, coherence must surely reside in the dreamer's felt involvement in those dream events, and this is virtually impossible to determine from a dream report. Second, in response to Hobson's claim that a purely associative thought process neglects the role of dissociation, I argue that metaphor (analogical thinking in general), in all its forms, consists of a tension between resemblance and dissociation (a shift from one domain to another) and that the function of metaphor is, precisely, to free us from the gravity of received understanding. I suggest ways in which this process operates in all speculation, including art and science. Finally, I discuss the nature of dream orientation in connection with the specimen dream that Hobson provided.  相似文献   

5.
Sherwin S 《Bioethics》1999,13(3-4):198-205
I explore the implications of the foundation metaphor for understanding the role of moral theories in ethics and bioethics and argue that its disadvantages outweigh its advantages. I then consider two other metaphors that might be used instead, those of frameworks and lenses. I propose that the metaphor of lenses is most promising in providing methodological guidance for drawing on moral theories when deliberating about bioethical problems.  相似文献   

6.
Will Newsome 《Biosemiotics》2013,6(3):311-322
This paper is a methodological and theoretical meditation on how some research has approached the question of the evolution of human cognitive traits. I discuss views that explicitly or implicitly endorse a view of human cognition as originating from a cause that can be singled out. Following Ross and Ladyman (2010), I suggest that this “singling-out” strategy correlates with a “container” metaphor that doesn’t fit with the interactive process-ontology of modern physics (Campbell 2009). Instead, Ross and Ladyman as well as Campbell recommend the metaphor of ‘emergence’. The logic and ontology of emergent systems finds resonance with developmental systems theory in biology. I suggest in agreement with Stotz (Phenomenology and the Cognitive Sciences 9(4), 2010) that we view the origins of human mindedness within such a framework.  相似文献   

7.
Production of a raw starch-digesting glucoamylase O (GA O) by protease-negative, glycosidase-negative mutant strain HF-15 of Aspergillus awamori var. kawachi was undertaken under submerged culture conditions. The purified GA O was electrophoretically homogeneous and similar to the parent glucoamylase I (GA I) in the hydrolysis curves toward gelatinized potato starch, raw starch, and glycogen and in its thermostability and pH stability, but it was different in molecular weight and carbohydrate content (250,000 and 24.3% for GA O, 90,000 and ca. 7% for GA I, respectively). The chitin-bound GA O hydrolyzed raw starch but the chitin-bound GA I failed to digest raw starch because chitin was adsorbed at the raw starch affinity site of the GA I molecule. The removal of the raw starch affinity site of GA O with subtilisin led to the formation of a modified GA O (molecular weight, 170,000), which hydrolyzed glycogen 100%, similar to GA O and GA I, and was adsorbed onto chitin and fungal cell wall but not onto raw starch, Avicel, or chitosan. The modified GA I (molecular weight, 83,000) derived by treatment with substilisin hydrolyzed glycogen up to only 80% and failed to be adsorbed onto any of the above polysaccharides. The N-bromosuccinimide-oxidized GA O lost its activity toward gelatinized and raw starches, but the abilities to be adsorbed onto raw starch and chitin were preserved. It was thus suggested that both the raw starch affinity site essential for raw starch digestion and the chitin-binding site specific for the binding with chitin in the cell wall could be different from the active site, located in the three respective positions in the GA O molecule.  相似文献   

8.
A close correspondence has been demonstrated between double filaments of deoxygenated hemoglobin S molecules as found in monoclinic crystals, forms I and II, and in sickle fibers. We have carried out a low resolution study of monoclinic form II by X-ray diffraction analysis. Its structure differs from that of form I solely by a shift along the a-axis of the molecular centers of the asymmetric unit, which forms the double filament. The magnitude of the translation was determined from a minimum residual calculation. The x co-ordinates of the symmetry related molecular centers of antipolar double filaments are approximately the same. This means that the double filaments are nearly in register. A minor component associated with form II crystals proved to be form I. The possible existence of additional forms is discussed.The significance of the molecular arrangement in form II is related to its presence in sickle fibers. We have determined the contacts between antipolar double filaments in this form as well as a number in form I not tabulated previously. These new contacts represent additional stabilizing interactions that might provide targets for the design of stereospecific antisickling agents.  相似文献   

9.
Biological specificity is usually described in terms of the lock-and-key metaphor. However, this metaphor is to a certain extent misleading and does not grasp the complexity underlying biological specificity. The failure of the lock-and-key metaphor makes it difficult to understand immune recognition. This is the reason why immune specificity has been described as the "Specificity Enigma." In this article, I point at three important differences between biological specificity and mechanical specificity, and suggest an alternative lens through which immune specificity can be considered.  相似文献   

10.
Chemical machines, Maxwell's demon and living organisms   总被引:4,自引:0,他引:4  
The problem considered in this paper is whether conventional chemical machines can be used in living organisms. I first point out that, due to their molecular nature, living systems pose unique thermodynamic problems, particularly in relation to Maxwell's demon. I then show that these problems may be solved by introducing time into the fundamental statement of the second law so that it becomes valid at the molecular level. This proposal, while clarifying certain logical anomalies in classical thermodynamics, makes no difference to that science in practice. However, I deduce from this statement that there are only two general ways of obtaining useful work from a chemical reaction: the first, a “constrained equilibrium” mechanism, is that employed by conventional chemical engines, but the second, a “molecular energy” mechanism, which depends upon the rapidity of resonant energy-transfer, may not have been suggested before. I then argue that because the former mechanism is essentially macroscopic in character it cannot, in fact, be used in those biological processes, like muscular contraction or active transport, in which useful molecular work is done and that only the latter may be so used. I also suggest reasons why this conclusion has been overlooked. Muscular contraction is used to illustrate these arguments and it is shown that all models of this process so far proposed fall into the first category. Although it is possible to eliminate such models a priori, several examples are finally criticized in detail to clarify the points raised. It is shown that in fact each of these models would have to be a Maxwell's demon machine.  相似文献   

11.
The DNA of the nuclear polyhedrosis virus of the alfalfa looper, Autographa californica (AcNPV), has been analyzed with restriction endonucleases BamHI and SmaI. The molecular weight of the BamHI fragments, SmaI fragments, and BamHI + SmaI fragments has been determined. The molecular weight of AcNPV DNA is calculated to be about 82 million. A presumptive physical map of the BamHI and SmaI restriction sites on the AcNPV genome has been constructed.  相似文献   

12.
I examine the relationship between evolutionary definitions of altruism that are based on fitness effects and psychological definitions that are based on the motives of the actor. I show that evolutionary altruism can be motivated by proximate mechanisms that are psychologically either altruistic or selfish. I also show that evolutionary definitions do rely upon motives as a metaphor in which the outcome of natural selection is compared to the decisions of a psychologically selfish (or altruistic) individual. Ignoring the precise nature of both psychological and evolutionary definitions has obscured many important issues, including the biological roots of psychological altruism.  相似文献   

13.
Vorticella includes more than 100 currently recognized species and represents one of the most taxonomically challenging genera of ciliates. Molecular phylogenetic analysis of Vorticella has been performed so far with only sequences coding for small subunit ribosomal RNA (SSU rRNA); only a few of its species have been investigated using other genetic markers owing to a lack of similar sequences for comparison. Consequently, phylogenetic relationships within the genus remain unclear, and molecular discrimination between morphospecies is often difficult because most regions of the SSU rRNA gene are too highly conserved to be helpful. In this paper, we move molecular systematics for this group of ciliates to the infrageneric level by sequencing additional molecular markers—fast-evolving internal transcribed spacer (ITS) regions—in a broad sample of 66 individual samples of 28 morphospecies of Vorticella collected from Asia, North America and Europe. Our phylogenies all featured two strongly supported, highly divergent, paraphyletic clades (I, II) comprising the morphologically defined genus Vorticella. Three major lineages made up clade I, with a relatively well-resolved branching order in each one. The marked divergence of clade II from clade I confirms that the former should be recognized as a separate taxonomic unit as indicated by SSU rRNA phylogenies. We made the first attempt to elucidate relationships between species in clade II using both morphological and multi-gene approaches, and our data supported a close relationship between some morphospecies of Vorticella and Opisthonecta, indicating that relationships between species in the clade are far more complex than would be expected from their morphology. Different patterns of helix III of ITS2 secondary structure were clearly specific to clades and subclades of Vorticella and, therefore, may prove useful for resolving phylogenetic relationships in other groups of ciliates.  相似文献   

14.
Isonicotinic acid hydrazide (Isoniazid, INH) is one of the major drugs worldwide used in the chemotherapy of tuberculosis. Many investigators have emphasized that INH activation is associated with mycobacterial catalase-peroxidase (katG). However, INH activation mechanism is not completely understood. In this study, katG of M. bovis BCG was separated and purified into two katGs, katG I (named as relatively higher molecular weight than katG II) and katG II, indicating that there is some difference in protein structure between two katGs. The molecular weight of the enzymes of katG I and katG II was estimated to be approximately 150,000 Da by gel filtration, and its subunit was 75,000 Da as determined by SDS-PAGE, indicating that purified enzyme was composed of two identical subunits. The specific activity of the purified enzyme katG I was 991.1 (units/mg). The enzymes were then investigated in INH activation by using gas chromatography mass spectrometry (GC-MS). The analysis of GC-MS showed that the katG I from M. bovis BCG directly converted INH (Mr, 137) to isonicotinamide (Mr, 122), not to isonicotinic acid (Mr, 123), in the presence or absence of H2O2. Therefore, this is the first report that katG I, one of two katGs with almost same molecular weight existed in M. bovis BCG, converts INH to isonicotinamide and this study may give us important new light on the activation mechanism of INH by KatG between M. bovis BCG and M. tuberculosis.  相似文献   

15.
In this study, internal transcribed spacer (ITS) regions within the nuclear ribosomal DNA of KoreanIlex were analyzed in order to investigate any molecular evidence thatI. × wandoensis could serve as a putative hybrid betweenI. cornuta andI. integra. We also sought to clearly identify taxonomic relationships and problems caused by consecutive external morphological characters among taxa in the genus. We sequenced 20 clones fromI. × wandoensis and found these individuals displayed intra-genomic polymorphisms within ITS regions. The analysis of the clones clearly demonstrated the presence of discrete sequences from bothI. cornuta andI. integra, thereby confirmingI. × wandoensis is a species that was formed by crossingI. cornuta andI. integra. Lastly, the subgenusIlex, which contains the evergreen species, failed to form a monophyletic group in a strict consensus tree that was prepared based upon ITS regions.I. crenata var.microphylla in the subgenus KoreaIlex, which has presented taxonomic problems previously, formed an independent clade within the consensus tree, thereby showing distinction fromI. crenata.) Genetic discontinuity ofI. macropoda andI. Macropoda for.pseudo-macropoda individuals couldn't be confirmed.  相似文献   

16.
Development of in vitro culture protocol for early stage ovarian follicles of zebrafish is important since cryopreserved early stage ovarian follicles would need to be matured in vitro following cryopreservation before they can be fertilised. Development of molecular markers for zebrafish (Danio rerio) ovarian follicle growth assessment following in vitro culture of early stage zebrafish ovarian follicles in ovarian tissue fragments is reported here for the first time although some work has been reported for in vitro culture of isolated early stage zebrafish ovarian follicles. The main aim of the present study was to develop molecular markers in an optimised in vitro culture protocol for stage I and stage II zebrafish ovarian follicles in ovarian tissue fragments. The effect of concentration of the hormones human chorionic gonadotropin and follicle stimulating hormones, and additives such as Foetal Bovine Serum and Bovine Serum Albumin were studied. The results showed that early stage zebrafish ovarian fragments containing stage I and stage II follicles which are cultured in vitro for 24 h in 20% FBS and 100mIU/ml FSH in 90% L-15 medium at 28 °C can grow to the size of stage II and stage III ovarian follicles respectively. More importantly the follicle growth from stage I to stage II and from stage II to stage III were confirmed using molecular markers such as cyp19a1a (also known as P450aromA) and vtg1 genes respectively. However, no follicle growth was observed following cryopreservation and in vitro culture.  相似文献   

17.
《Reproductive biology》2022,22(4):100705
Type I collagen is the most abundant extracellular matrix (ECM) protein in the mammalian ovary, and comprises two COL1A1 subunits and one COL1A2 subunit. Matrix metalloproteinase 1 (MMP1) is a typical collagenase of type I collagen, that can be detected in ovarian follicles and early corpus luteum. Previous studies demonstrated that MMP1-mediated degradation of type I collagen plays a functional role in regulating corpus luteum formation, and transforming growth factor β1 (TGF-β1) inhibits luteinization and progesterone production in granulosa cells (GCs). Whether TGF-β1 regulates the expression of MMP1, COL1A1, or the deposition of type I collagen during corpus luteum formation remains to be elucidated. This study aimed to investigate the molecular mechanisms through which TGF-β1 regulates MMP1 expression and type I collagen deposition in GCs. Our results show that TGF-β1 upregulates COL1A1 expressions and downregulates MMP1 expression. Inhibition approaches, including pharmacological inhibitors such as p38 inhibitor (SB203580), ERK1/2 inhibitor (U0126), AKT inhibitor (LY294002), and GSK-3β inhibitor (LiCl), as well as knockdown using siRNA specific to these genes, were used. Our results suggest that TGF-β1 decreases MMP1 production via an ALK5-mediated AKT/GSK-3β-dependent signaling pathway, and a decrease in MMP1 levels and an increase in COL1A1 levels synergistically promote type I collagen deposition in GCs. Collectively, these findings provide novel insights into the underlying molecular mechanisms by which TGF-β1 upregulates type I collagen deposition in GCs.  相似文献   

18.
19.
Two cationic proteins, C1 and C3, were purified to homogeneity from the hemolytic fraction of the venom of Bunodosoma caissarum sea anemone. The purification processes employed gel filtration followed by ion exchange chromatography, being the purity and molecular mass confirmed by SDS-PAGE and mass spectrometry. Protein C1 represented the second major peak of the hemolytic fraction and was previously believed to be a cytolysin belonging to a new class of hemolysins. The C1 protein has a molecular mass of 15495 Da and was assayed for hemolysis, PLA2 activity and acute toxicity in crabs and mice, showing no activity in these assays. It has an amino terminal with no similarity to all known hemolysins and, therefore, should not be considered a toxin, being its function completely unknown. The protein C3 (19757 Da), that also lacks PLA2 activity, was recognized by antiserum against Eqt II and presented high hemolytic activity to human erythrocytes (ED50 of 0.270 μg/ml), being named Caissarolysin I (Bcs I). Its activity was inhibited by pre-incubation with sphingomyelin (SM) and also when in presence of erythrocytes pre-treated with the SMase P2, a phospholipase D from the brown spider Loxosceles intermedia, indicating that SM is the main target of Bcs I. Caissarolysin I is the first hemolysin purified from a sea anemone belonging to the genus Bunodosoma and belongs to the Actinoporin family of sea anemone hemolysins.  相似文献   

20.
Hepatic cytosolic arginase (ARG I), an enzyme of the urea cycle operating in the liver of ureotelic animals, is reported to be present in an ammoniotelic freshwater air-breathing teleost, Heteropneustes fossilis which has ureogenic potential. Antibodies available against mammalian ARG I showed no cross reactivity with the H. fossilis ARG I. We purified unique ARG I from H. fossilis liver. Purified ARG I is a homotrimer with molecular mass 75 kDa and subunit molecular mass of 24 kDa. The pI value of the enzyme was 8.5. It showed maximum activity at pH 10.5 and 55°C. The Km of purified enzyme for L-arginine was 2.65±0.39 mM. L-ornithine and Nω-hydroxy-L-arginine showed inhibition of the ARG I activity, with Ki values 0.52±0.02mM and 0.08±0.006mM, respectively. Antibody raised against the purified fish liver ARG I showed exclusive specificity, and has no cross reactivity against fish liver ARG II and mammalian liver ARG I and ARG II. We found another isoform of arginase bound to the outer membrane of the mitochondria which was released by 150–200 mM KCl in the extraction medium. This isoform was immunologically different from the soluble cytosolic and mitochondrial arginase. The results of present study support that hepatic cytosolic arginase evolved in this ureogenic freshwater teleost, H. fossilis. Phylogenetic analysis confirms an independent evolution event that occurred much after the evolution of the cytosolic arginase of ureotelic vertebrates.  相似文献   

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