Hereditary Variation Research Articles

Hereditary Factors and Tooth Dimensions: A Twin Study

Introduction : Determination of the actual level of genetic determinance of occlusal variation could have a significant effect on prognosis and treatment planning. Aim: The objective of this study was to evaluate the hereditary variations occurring among the members within monozygotic and dizygotic twin pairs based on widest mesiodistal measurements in relation to the posterior permanent dentition. Materials and methods: Twenty-eight adult twin pairs (16 monozygotic pairs, 12 dizygotic pairs) in the age group of 14 to 55 years were used for the study. Mesiodistal measurements of maxillary and mandibular permanent posterior teeth at their maximum width were considered. Intrapair differences were calculated, the differences in the two groups were compared and the level of significance was tested. Results: Significant differences between the twin groups was found in relation to all the teeth studied except the maxillary and mandibular second molars. Conclusion: Genetically conditioned variations of highly significant nature were seen in 12 of the 16 posterior teeth studied, thereby confirming the evidence that size of teeth is under genetic control.

RNA–Mediated Epigenetic Heredity Requires the Cytosine Methyltransferase Dnmt2

RNA–mediated transmission of phenotypes is an important way to explain non-Mendelian heredity. We have previously shown that small non-coding RNAs can induce hereditary epigenetic variations in mice and act as the transgenerational signalling molecules. Two prominent examples for these paramutations include the epigenetic modulation of the Kit gene, resulting in altered fur coloration, and the modulation of the Sox9 gene, resulting in an overgrowth phenotype. We now report that expression of the Dnmt2 RNA methyltransferase is required for the establishment and hereditary maintenance of both paramutations. Our data show that the Kit paramutant phenotype was not transmitted to the progeny of Dnmt2−/− mice and that the Sox9 paramutation was also not established in Dnmt2−/− embryos. Similarly, RNA from Dnmt2-negative Kit heterozygotes did not induce the paramutant phenotype when microinjected into Dnmt2-deficient fertilized eggs and microinjection of the miR-124 microRNA failed to induce the characteristic giant phenotype. In agreement with an RNA–mediated mechanism of inheritance, no change was observed in the DNA methylation profiles of the Kit locus between the wild-type and paramutant mice. RNA bisulfite sequencing confirmed Dnmt2-dependent tRNA methylation in mouse sperm and also indicated Dnmt2-dependent cytosine methylation in Kit RNA in paramutant embryos. Together, these findings uncover a novel function of Dnmt2 in RNA–mediated epigenetic heredity.

Improvement Efficiency of Recurrent Selection for the Combining Ability of Yield Trait in Maize Population Yuzong 5

Maize population has the extensive hereditary basis and rich hereditary variation,and therefore is the source of good inbred lines cultivated.Improvement of maize population is important to create new germplasm and breed excellent inbred lines.In this study,30 testcrossing combinations that Huangzaosi,Dan 340,Zhong Syn 5,Qi 319,Ye 478,and Mo17 crossed with five cycle improved populations according to NC II design were evaluated in two environments.The results showed that the recurrent selection method gained a good result for yield per plant of the population and the gain of hybrid grain yields of testcross combi-nations between improved populations per cycle and testing cultivars increased by 10%.Both half-sib recurrent selection(HS-RS) and half-sib reciprocal recurrent selection(HS-RRS) were good methods for improving the general combining ability(GCA) of grain yield in the populations and the GCA was improved in very cycle for the populations.After improvement of three cycles for Yuzong 5 by HS-RS,the GCA increased from -11.63 to 5.57 with highly significant probability difference at the level by C3 comparing with C0.After improvement of one cycle for Yuzong 5 by HS-RRS,the GCA increased from 5.57 to 9.75 by C4 com-paring with C3.The analysis of special combining ability(SCA) showed that the SCA of improved Yuzong 5 × Huangzaosi had certain enhancement,indicating that improvement of Yuzong 5 developed steadily toward the heterotic pattern of Reid×SiPT.

Domestication and N.I. Vavilov’s law of homologous series in hereditary variability

Domestication traits in animal and plant species distinguishing them from closely related wild species are discussed. Data are given on what such traits are found not only at the phenotypic level but also in polymorphism of electrophoretic variants of protein groups with a different biochemical function, DNA fragments flanked by inverted short repeats. The assumption that retrovirus infections can participate in the formation of domestication traits is substantiated.

Something about Genetics in Psychiatry

Something about Genetics in Psychiatry

What is comparable in comparative cognition?

To understand how complex, or 'advanced' various forms of cognition are, and to compare them between species for evolutionary studies, we need to understand the diversity of neural-computational mechanisms that may be involved, and to identify the genetic changes that are necessary to mediate changes in cognitive functions. The same overt cognitive capacity might be mediated by entirely different neural circuitries in different species, with a many-to-one mapping between behavioural routines, computations and their neural implementations. Comparative behavioural research needs to be complemented with a bottom-up approach in which neurobiological and molecular-genetic analyses allow pinpointing of underlying neural and genetic bases that constrain cognitive variation. Often, only very minor differences in circuitry might be needed to generate major shifts in cognitive functions and the possibility that cognitive traits arise by convergence or parallel evolution needs to be taken seriously. Hereditary variation in cognitive traits between individuals of a species might be extensive, and selection experiments on cognitive traits might be a useful avenue to explore how rapidly changes in cognitive abilities occur in the face of pertinent selection pressures.

Evolvable Physical Self-Replicators

Building an evolvable physical self-replicating machine is a grand challenge. The main problem is that the device must be capable of hereditary variation, that is, replicating in many configurations-configurations into which it enters unpredictably by mutation. Template replication is the solution found by nature. A scalable device must also be capable of miniaturization, and so have few or no moving and electronic parts. Here a significant step toward this goal is presented in the form of a physical template replicator made from small plastic pieces containing embedded magnets that float on an air-hockey-type table and undergo stochastic motion. Our units replicate by a process analogous to the replication of DNA, except without the involvement of enzymes. Building a physical rather than a computational model forces us to confront several problems that have analogues on the nano scale. In particular, replication must be maintained by preventing side reactions such as spontaneous ligation, cyclization, product inhibition, and elongation at staggered ends. The last of these results in ever-lengthening sequences in a process known as the elongation catastrophe. The extreme specificity of structure required by the monomers is indirect evidence that some kind of natural selection took place prior to the existence of nucleotide analogues during the origin of life.

Selectionist and Evolutionary Approaches to Brain Function: A Critical Appraisal

We consider approaches to brain dynamics and function that have been claimed to be Darwinian. These include Edelman’s theory of neuronal group selection, Changeux’s theory of synaptic selection and selective stabilization of pre-representations, Seung’s Darwinian synapse, Loewenstein’s synaptic melioration, Adam’s selfish synapse, and Calvin’s replicating activity patterns. Except for the last two, the proposed mechanisms are selectionist but not truly Darwinian, because no replicators with information transfer to copies and hereditary variation can be identified in them. All of them fit, however, a generalized selectionist framework conforming to the picture of Price’s covariance formulation, which deliberately was not specific even to selection in biology, and therefore does not imply an algorithmic picture of biological evolution. Bayesian models and reinforcement learning are formally in agreement with selection dynamics. A classification of search algorithms is shown to include Darwinian replicators (evolutionary units with multiplication, heredity, and variability) as the most powerful mechanism for search in a sparsely occupied search space. Examples are given of cases where parallel competitive search with information transfer among the units is more efficient than search without information transfer between units. Finally, we review our recent attempts to construct and analyze simple models of true Darwinian evolutionary units in the brain in terms of connectivity and activity copying of neuronal groups. Although none of the proposed neuronal replicators include miraculous mechanisms, their identification remains a challenge but also a great promise.

Study on the pathological and molecular characteristics of viral meningitis outbreaks in Linhai county, Zhejiang province, 2004

In order to confirm the causes of viral meningitis outbreaks in Linhai county, Zhejiang province in 2004, and to analyze the relationship between hereditary variation and evolution of the pathogen. 60 cerebrospinal fluid (CSF) specimens were collected from the suspected patients. Virus strains from the specimens were isolated with RD and Hep-2 cell lines, and identified through neutralization test. VP1 and VP4/VP2 genes of the isolated viruses were sequenced. Both phylogenetic and homological trees were also constructed. 19 Echovirus type 30 (E30) strains were isolated from 60 CSFs, in which E30 accounted for 31.7%. All of the complete VP1 genes in 4 sequenced virus isolates of E30 were composed of 876 nt, encoding 292 amino acids (aa). The identity of nucleotide and amino acid in VP1 gene were 82.4% - 84.1% and 93.5% - 94.2% between the 4 Linhai strains and the prototype strain Bastianni of E30, were 87.1% - 99.9% and 97.9% - 100.0% among the 4 virus strains of E30 from Linhai, respectively. The 4 Linhai strains could be classified into two classes. The diversity of nt and aa was minimal in the same class but obvious between the two classes, with the range of diversities as 12.9% and 2.1%, respectively. The Linhai E30 strains had maximum similarity with the Zhejiang E30 strains in 2002 - 2003. The 4 Linhai strains of E30 in the phylogenetic tree of the VP1 gene were attributed into two branches of the G and H genotype, respectively. The G branch also included the E30 strains from Zhejiang, Jiangsu and Shangdong in 2003, while the H branch including E30 strains from Zhuji, Zhejiang in 2002. The phylogenetic tree of VP4/VP2 genes was similar to that of VP1 gene. The outbreak of viral meningitis in Linhai county in 2004 was caused by the two classes of E30 strains with G and H genotype existed simultaneously. The Linhai E30 strains had maximum genetic relations to the Zhejiang, Jiangsu and Shangdong strains of E30. The H genotype was inferred to be a new variant strain, which was first isolated in Zhejiang province in 2002.

Evolvable Neuronal Paths: A Novel Basis for Information and Search in the Brain

We propose a previously unrecognized kind of informational entity in the brain that is capable of acting as the basis for unlimited hereditary variation in neuronal networks. This unit is a path of activity through a network of neurons, analogous to a path taken through a hidden Markov model. To prove in principle the capabilities of this new kind of informational substrate, we show how a population of paths can be used as the hereditary material for a neuronally implemented genetic algorithm, (the swiss-army knife of black-box optimization techniques) which we have proposed elsewhere could operate at somatic timescales in the brain. We compare this to the same genetic algorithm that uses a standard ‘genetic’ informational substrate, i.e. non-overlapping discrete genotypes, on a range of optimization problems. A path evolution algorithm (PEA) is defined as any algorithm that implements natural selection of paths in a network substrate. A PEA is a previously unrecognized type of natural selection that is well suited for implementation by biological neuronal networks with structural plasticity. The important similarities and differences between a standard genetic algorithm and a PEA are considered. Whilst most experiments are conducted on an abstract network model, at the conclusion of the paper a slightly more realistic neuronal implementation of a PEA is outlined based on Izhikevich spiking neurons. Finally, experimental predictions are made for the identification of such informational paths in the brain.

A large proportion of esophageal cancer cases and the incidence difference between regions are attributable to lifestyle risk factors in China

A population-based case-control study was conducted in a high-risk area (Dafeng) and a low-risk area (Ganyu) of Jiangsu province, China. In this analysis, the population attributable fraction (PAF) was calculated to quantify the etiology of risk factors; the relative attributable risk (RAR) was applied to explore how much of the incidence difference could be explained by variations in the distribution of risk factors. Results showed that unhealthy lifestyles accounted for a high fraction of esophageal cancer in China. Dissimilar distribution of several lifestyle factors, together with hereditary variations may be largely responsible for the incidence difference between areas.

Félix de Azara, crítico de Buffon

En sus "Apuntamientos para la Historia Natural de los Cuadrúpedos del Paraguay y Río de la Plata", de 1802, Félix de Azara (1742-1821) no sólo corrigió la identificación y descripción de muchas especies sudamericanas hechas por Buffon; él también desarrolló argumentos contrarios a la tesis de Buffon según la cual el clima sudamericano estimulaba la degeneración de los seres vivos. Pero además de eso, Azara también esbozó una explicación del surgimiento de variedades al interior de una especies que, en lugar de apelar a los efectos directos del clima y la alimentación, recurría al surgimiento de variaciones hereditarias fortuitas. Esta última teoría era una conjetura alternativa a la teoría de la degeneración propuesta por Buffon y retomada, aunque de un modo atenuado, por la mayor parte de los naturalistas anteriores a Darwin.

Phenogenetic analysis of testicular responsiveness to chorionic gonadotropin in inbred mouse strains

Genetic differences in the testicular hormonal responsiveness to in vivo administration of chorionic gonadotropin (CG) between adult male mice of eight inbred strains (A/Sn, CBA/Lac, CC57Br, C57Bl/6J, DBA/2J, GR, PT, and YT) were determined. In addition, the genetic variation of the body and testis weights was estimated as related to the responsiveness to stimulation of steroidogenesis with CG. Adult males were subcutaneously injected with 10 IU of CG or physiological saline 120 min before decapitation. It was found that the baseline testosterone level in the blood serum and its content in the testes only slightly varied in males of the strains studied. Administration of CG increased these parameters by a factor of 3-45, depending on the strain. The results of the study indicate genetic differences in the testicular reactivity to CG. In addition, it has been found that the response to administration of CG, as compared to the baseline levels, provides the most reliable information on the genetic characteristics of the hormonal potential of the testes. The given set of inbred mouse strains may be a promising genetic model for studying the physiological and hereditary variations of testicular steroidogenesis.

Variability, template principle, and evolutionary theory

The central dogma of molecular biology (Crick, 1958, 1970), as an expression of the template principle in biology, provides a basis for the consideration of different variability types connected with replication, transcription, and translation from the unified position. There are also conformational templates (the second order templates), which should be considered in addition to the generally accepted templates of the first order. Nevertheless, there is no direct correspondence between molecular mechanisms and organismic (phenotypic) manifestation of variability types. This explains contradictions in the commonly accepted classification of variability types. Uniform mechanisms may underlie both hereditary and nonhereditary variations, depending on the taxonomic position and stage of the life cycle. Hereditary genetic and epigenetic variations differ in frequency and, hence, have different effect on the efficiency of natural selection, resulting in different tempos of evolution.

Association of goat (Capra hircus) CD4 gene exon 6 polymorphisms with ability of sperm internalizing exogenous DNA

As one of the transport systems on the sperm plasma membrane, CD4 molecule plays a distinct role in the process of sperm/DNA interaction. This makes it possible to explain the mechanism of sperm-mediated gene transfer (SMGT), which at present is still a mystery in this area. In this study, seminal samples of 60 individuals from seven breed bucks were collected to detect the ability of sperm in internalizing exogenous DNA, and genomic DNA from 147 individual blood samples (including 60 bucks referred ahead) were extracted to test the polymorphisms of CD4 genes by using PCR-SSCP technique. Then the correlation between them was evaluated. The results showed that: (1) it was a novel finding that breed-dependence of exogenous DNA binding to goat spermatozoa. There was the most significant difference among the buck breeds of sperm in binding exogenous DNA (F((6, 53)) = 4.811, P = 0.001) and in internalizing them into nuclei (F((6, 53)) = 4.587, P = 0.001). The ability of Lezhi Black goat was the lowest (P < 0.01) among the seven breeds. (2) There was no significant correlation between the ability of sperm in internalizing exogenous DNA and each semen quality parameter (P > 0.05). (3) In particular, three single-nucleotide polymorphisms (SNP) were described and there was one SNP (G/A(700)) of CD4 gene that made G234R substitution in the amino acid sequence of CD4 molecule. Nanjiang Yellow goat and Lezhi Black goat had higher hereditary variation compared with other breeds. (4) CD4 polymorphisms were highly associated with the ability of sperm in internalizing exogenous DNA. The SNP of Caprine CD4 gene exon 6 might be an important molecular marker of the ability to internalize exogenous DNA into sperm.

Chromatin regulators shape the genotype–phenotype map

Mol Syst Biol. 6: 434 Whereas mechanistic developmental biology and evolutionary genetics largely proceeded independently from each other throughout most of the twentieth century, new discoveries and technologies have made it possible to revisit longstanding questions of how molecular mechanisms generate the phenotypic effects of alternative alleles. Pioneers such as Schmalhausen (1949) emphasized that phenotypic variation can often be surprisingly limited to both within and between species and proposed that the process of development and its genetic underpinnings are organized to allow a ‘reserve of hereditary variability’ to accumulate within a species that can then be mobilized when conditions change . We are now in a position to dissect the molecular mechanisms that generate the apparent mismatch between extensive genetic and limited phenotypic variation. One important milestone was the discovery that knocking out the activity of the molecular chaperone Hsp90 results in an efflorescence of phenotypic variation due to the exposure of underlying genetic variation. The effects of new mutations are context dependent, and functional Hsp90 dramatically reduces these effects under normal conditions (Rutherford and Lindquist, 1998). Such genes that allow variation to accumulate without having an effect have been dubbed capacitors (Figure 1). In a recent article published in Molecular Systems Biology , Tirosh et al (2010) provide new evidence that chromatin …

The problem of stability of organisms after cryopreservation (fungi as example)

The results of research on the consequences of cryoconservation of fungi indicating the stability of their morphology are reviewed, and a number of facts indicating the changes in the properties of the fungus and the mutagenicity of cryopreservation are presented. The investigations of the last ten years confirm the Rosanov's hypothesis according to which cryoconservation must lead to an increase in the reserve of the hereditary variation of organisms.

Corrections to chance fluctuations: quantum mind in biological evolution?

According to neo-Darwinian theory, biological evolution is produced by natural selection of random hereditary variations. This assumption stems from the idea of a mechanical and deterministic world based on the laws of classic physics. However, the increased knowledge of relationships between metabolism, epigenetic systems, and editing of nucleic acids suggests the existence of self-organized processes of adaptive evolution in response to environmental stresses. Living organisms are open thermodynamic systems which use entropic decay of external source of electromagnetic energy to increase their internal dynamic order and to generate new genetic and epigenetic information with a high degree of coherency and teleonomic creativity. Sensing, information processing, and decision making of biological systems might be mainly quantum phenomena. Amplification of microscopic quantum events using the long-range correlation of fractal structures, at the borderline between deterministic order and unpredictable chaos, may be used to direct a reproducible transition of the biological systems towards a defined macroscopic state. The discoveries of many natural genetic engineering systems, the ability to choose the most effective solutions, and the emergence of complex forms of consciousness at different levels confirm the importance of mind-action directed processes in biological evolution, as suggested by Alfred Russel Wallace. Although the main Darwinian principles will remain a crucial component of our understanding of evolution, a radical rethinking of the conceptual structure of the neo-Darwinian theory is needed.

An alternative approach to medical genetics based on modern evolutionary biology. Part 1: mutation and symbiogenesis.

The need to understand the genetic underpinning of common diseases, such as cancer, diabetes and autoimmune disorders, is a major challenge facing medical genetics. While many disorders involve a complex interaction between genetic traits and environmental influences, a significant proportion involve specific genetic causes that are diagnosable and thus amenable to therapeutic approaches, including family counselling, specific lines of chemically-directed therapy and even the possibility of addressing the underlying genetic causation through specific genetic therapy. The genetic approach to medicine has always found commonalities with the disciplines of evolutionary biology: only when we understand the evolutionary origins of the human genome can we aspire to understand how ‘normality’, in terms of genetics and epigenetics, becomes subverted in disease. Since the 1930s, mutation has been assumed to be the exclusive explanation of the hereditary basis of disease. But advances in evolutionary biology over the last two decades have introduced three additional, and important, sources of hereditary variation, namely symbiogenesis, particularly symbiogenesis involving viruses, epigenetics and hybridogenesis, all of which are now seen to have played important roles in the evolution of biodiversity. These additional mechanisms have played a major role in the evolution of the human genome – indeed they help to explain what would otherwise appear to be some paradoxical aspects of its construction and make-up. In this paper, and the four linked papers that follow it, I shall explain the evolutionary advances and show how, together with the knowledge already accrued from the study of mutation, they provide a more comprehensive understanding of the hereditary basis of human disease.

Darwin at 200

Darwin is deservedly credited as the originator of the modern theory of evolution. In Origin he gathered the best available evidence for evolution: 2 chapters dedicated to the geological record, 2 chapters to biogeography, and 1 chapter to comparative anatomy and embryology. The other 9 chapters (I–VIII and XIII) are mostly dedicated to natural selection, the process that accounts for the adaptation, common descent, and diversity of organisms. He explains how natural selection works, discusses the role of hereditary variation (the mechanics of which were not well understood in Darwin's time), and considers possible objections to his theory.