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PubMed2005

Two new mouse mutants with vestibular defects that map to the highly mutable locus on chromosome 4.

The purpose of this study was to characterise two new mouse mutants, carousel, and whirligig. Both were derived from a large-scale mutagenesis programme which screened for dominantly inherited mutations that cause hearing impairments and balance defects. Genetic mapping placed both mutations on the proximal region of chromosome 4. Paint-filling and clearing techniques revealed abnormalities of the lateral semicircular canal. Scanning electron microscopy showed increased numbers of outer and inner hair cells in the apical region of the organ of Corti. The behavioural, genetic, and morphological characteristics lead us to the conclusion that both mutants are probably alleles of seven previously identified mutants which all map to proximal chromosome 4 and share similar defects of the lateral semicircular canal. We suggest that this region may be particularly susceptible to ENU mutagenesis independent of genetic background.

Animals↗
PubMed1995

Biology of Saryupari Brahmins of Chhattisgarh, central India.

In July-November, 1986, Saryupari Brahmins of Chhattisgarh (Central India) have been investigated for the distribution of ABO blood groups, Rh factor, ABH secretion, PTC taste sensitivity and seven morphological traits. The important findings in brief are as follows: 1. The frequency of O blood group is slightly dominant (38.91%) and gene frequency exhibit r > q > p pattern. Statistical analysis (D/sigma = 0.5447) show that the population is in genetic equilibrium. 2. Estimation of the expected rate of erythroblastosis foetalis occurred in this population is calculated to be 8-16 cases in every 10,000 pregnancies. 3. High incidence (53.82%) of non-secretors of ABH substances in saliva suggest that this group may belong to Caucasoid stock. 4. The ability to taste the chemical PTC has a high frequency (61.81%) in this group. 5. R/L type of handclasping (58.15%), leg folding (65.38%) and L/R type of arm folding (58.93%) is dominant. L-type of handedness (5.48%) is moderately high. 6. Tongue rollers (93.28%) and folders (53.77%) are more among them. 7. Free type of ear lobe (68.68%) is the common feature in this population. 8. The above observations were compared in details with other Brahmin populations reported from India with special reference to the descendant groups residing in Madhya Pradesh (Central India). Furthermore, the results obtained on growth studies, and dermatoglyphic studies (palm and sole) from our published literature were also included so as to have some idea on the genetical, behavioural, dermatoglyphic and growth norms of this group.

ABO Blood-Group System↗
PubMed1992

Cytological aberrations in maize populations exhibiting unusual recombinational behaviour.

Earlier studies identified higher recombinational activity and increased somatic instability at various loci in the F1 and F2 progeny of particular stocks of a maize inbred line, A188. Hypothesizing that this may reflect a genome-wide perturbation of chromosome structure which would be detectable cytologically, aberrant meiotic behaviour in these stocks was investigated. Microsporocytes from a population of F2 plants derived from these stocks displayed the following aberrations: varying frequencies of metaphase and anaphase laggards, 'stickiness' at anaphase I resulting in chromosome bridges from pole to pole, acentric fragments and a spontaneous translocation of the NOR on chromosome 6. The frequencies of metaphase I and anaphase I abnormalities in these stocks were higher to a statistically significant extent than in control F2 populations, suggesting that these aberrations may be related to the unusual genetic behaviour of these stocks.

Anaphase↗
PubMed2006

The MC4 receptor and control of appetite.

Mutations in the human melanocortin (MC)4 receptor have been associated with obesity, which underscores the relevance of this receptor as a drug target to treat obesity. Infusion of MC4R agonists decreases food intake, whereas inhibition of MC receptor activity by infusion of an MC receptor antagonist or with the inverse agonist AgRP results in increased food intake. This review addresses the role of the MC system in different aspects of feeding behaviour. MC4R activity affects meal size and meal choice, but not meal frequency, and the type of diet affects the efficacy of MC4R agonists to reduce food intake. The central sites involved in the different aspects of feeding behaviour that are affected by MC4R signalling are being unravelled. The paraventricular nucleus plays an important role in food intake per se, whereas MC signalling in the lateral hypothalamus is associated with the response to a high fat diet. MC4R signalling in the brainstem has been shown to affect meal size. Further genetic, behavioural and brain-region specific studies need to clarify how the MC4R agonists affect feeding behaviour in order to determine which obese individuals would benefit most from treatment with these drugs. Application of MCR agonists in humans has already revealed side effects, such as penile erections, which may complicate introduction of these drugs in the treatment of obesity.

Agouti-Related Protein↗
PubMed2006

Identifying the genetic determinants of emotionality in humans; insights from rodents.

The identification of human quantitative trait genes underlying variation in emotionality has proved to be both difficult and expensive. Whilst several QTL have been consistently identified and independently replicated across both phenotypes and populations, little progression has been made towards the identification of underlying genes or even variants. In this review we discuss the potential for using cross-species QTL concordance as a tool for QTL dissection in behaviour genetics, using an affect-related locus mapped to human chromosome 1 as an example.

Animals↗
PubMed1996

Using MZ differences in the search for nonshared environmental effects.

Behavioural genetic research has shown that environmental influences relevant to the development of individual differences are largely nonshared in origin. That is, environmental influences do not make children in the same family similar to one another, however, little is known about which specific aspects of the environment are responsible. Identical (MZ) twins provide a uniquely powerful tool to search for specific nonshared environmental influences independent of nonshared genetics because such twins do not differ genetically. The sample consisted of 93 MZ twin pairs aged 10-18 years from the Nonshared Environment and Adolescent Development (NEAD) project. Reports of parental negativity and adolescent adjustment were obtained from parents, ratings of videotaped observations, and the adolescents themselves. Relative differences of mothers' and fathers' negativity within MZ pairs correlated significantly with MZ differences in antisocial behaviour. The correlations were moderate for within-reporter associations, but were negligible for associations between reporters. Possible interpretations for these source-specific findings are discussed.

Adolescent↗
PubMed1996

Mental retardation: genetic findings, clinical implications and research agenda.

The most important genetic advances in the field of mental retardation include the discovery of the novel genetic mechanism responsible for the Fragile X syndrome, and the imprinting involved in the Prader-Willi and Angelman syndromes, but there have also been advances in our understanding of the pathogenesis of Down syndrome and phenylketonuria. Genetic defects (both single gene Mendelizing disorders and cytogenetic abnormalities) are involved in a substantial proportion of cases of mild as well as severe mental retardation, indicating that the previous equating of severe mental retardation with pathology, and of mild retardation with normal variation, is a misleading over-simplication. Within the group in which no pathological cause can be detected, behaviour genetic studies indicate that genetic influences are important, but that their interplay with environmental factors, which are also important, is at present poorly understood. Research into the joint action of genetic and environmental influences in this group will be an important research area in the future.

Chromosome Aberrations↗
PubMed1992

Behaviour and the concept of "heritability" axioms of an ethological refutation.

This paper discusses the widespread use of heritability calculations in recent behaviour research including behaviour genetics. In the sequel, a radical criticism concerning the basic axioms of the underlying, more general concept itself is presented. The starting point for testing the proclaimed universal validity of this concept stems from a fictitious yet realistic example taken from learning research. The theoretical result, based on the application of the conventional reasoning in this field, states that developmental processes--and learning is only one specific case out of an immense number of similar behavioural mechanisms--can neither be adequately described nor causally explained with sufficient reliability within the context of the heredity paradigm. On the contrary, an inherent inconsistency of the concept itself when applied to behaviour processes is demonstrated. Finally, a conceptual alternative involving a systems-theoretical approach to the problem is presented: In such a perspective it is the concept of "cognition" which represents the adequate explanatory theorem--a theorem in which quantitative processing of "information" from the environment is clearly revealed to belong to a subordinate level of living organization.

Analysis of Variance↗
PubMed1986

[Principles and significance of genetically-induced variability of the normal human EEG].

This review describes the following results of human genetic research on the "normal" human EEG: As shown by comprehensive studies on mono- and dizygotic twins, interindividual variability of the human EEG under "normal" conditions is largely genetically determined. This was mainly shown for the resting EEG, but holds true also for the sleeping EEG, the reaction to ethanol, and for visually and auditory evoked potentials. Some fairly common EEG variants have been described which follow simple Mendelian modes of inheritance. Hence, they must go back to correspondingly simply differences in certain genes and gene-determined proteins. These variants have been useful as model systems for a neurobiologically founded research strategy in behaviour genetics of man. Comparative studies using psychological, neurophysiological (visual and auditory evoked potentials) and biochemical methods revealed group difference especially between carriers of the low-voltage EEG, the EEG with monomorphic alpha-waves and an EEG variant containing, in addition to alpha-waves, numerous diffuse beta-waves. Utilizing concepts from basic research in neurophysiology, they could be explained by corresponding differences in central information processing. Individual differences of EEG reaction are also observed after a controlled ethanol load. They have a genetic basis, too. An especially clearcut reaction of the EEG to alcohol can be seen in individuals with irregular alpha-activity of low amplitude in the resting EEG. Moreover, these persons appear to be especially susceptible for "learning" to become alcohol addicts. Individual variability in maturation during childhood and youth of brain structures responsible for EEG production are also under genetic control. This EEG maturation influences intellectual and psychic maturation.

Alpha Rhythm↗
PubMed1977

Transposable genetic elements as agents of gene instability and chromosomal rearrangements.

Transposable genetic elements in prokaryotes and eukaryotes, when inserted at a given locus, can control expression of the locus and cause large scale rearrangements of adjacent DNA sequences. Striking similarities in genetic behaviour between the two groups of elements have led to the proposal of a molecular model of eukaryotic controlling elements, and to suggestions about the part such elements may play in evolution and differentiation.

Base Sequence↗
PubMed1982

Rate of turnover of structural variants in the rDNA gene family of Drosophila melanogaster.

A high degree of polymorphism for the length and copy number of rDNA spacers, in both the X and Y chromosome clusters, has been found in a wild population of Drosophila melanogaster. The genetic behaviour of rDNA structural variants in separate and mixed populations derived from isofemale lines suggest that they are not subject to strong selection and are stable for over 1,000 generations. The high structural variability suggests an evolutionary rapid process of turnover in the family which could partly explain widespread sequence homogeneity (concerted evolution) of rDNA within a species.

Animals↗
PubMed2006

Evolutionary clues from comparative analysis of Mycobacterium tuberculosis variable-number tandem repeat sequences within genetic families.

Mycobacterium tuberculosis is one of the most successful bacterial pathogens in the history of mankind, and the study of the evolutionary and genetic behaviour of this organism is ongoing. The potential of variable-number tandem repeat (VNTR) regions to provide insight into the evolutionary past of this organism has yet to be evaluated. The aim of this study was to investigate diversity occurring within VNTR loci within established evolutionary lineages. Mycobacterial interspersed repetitive unit (MIRU) 4 and 26 nucleotide sequencing was undertaken revealing significant differences in VNTR discriminatory power and distribution of allelic types within defined sub-lineages, within a moderately discriminant and a highly discriminant locus, respectively. These findings indicate potential allele bias at these loci within the defined groups dependent on the genotype of their progenitor strain, and the patterns of distribution suggest that a step-wise contraction/expansion process is responsible for VNTR repeat evolution. The results also identified a possible incidence of genetic drift within major genetic group 2 (MGG2), which has a point mutation at locus MIRU26 in a clonal subgroup.

Amino Acid Sequence↗
PubMed2004

A cytogenetic method for stacking gene pairs in common wheat.

The potential for non-reciprocal Robertsonian translocations of wheat (Triticum aestivum L.) to assist in the stacking of genes was assessed from a study of their cytological and genetic behaviour. To obtain translocations, a double monosomic (3B+5A; 2n=40=19ii+2i) was crossed reciprocally with a contrasting disomic. Individuals inheriting a broken monosome were identified from the loss of one arm-specific DNA marker coupled with retention of a marker for the opposite arm. No double breaks (potential translocations) were found in 180 cross progeny recovered from pollen of the double monosomic but two instances (loss of 5AL plus 3BS; loss of 5AL plus 3BL) were found in 251 progeny recovered from ovules. Meiotic pairing and multi-color genome-specific fluorescence in situ hybridization (mcGISH) showed that each plant with a double break contained one translocated chromosome between the A and B genomes that had rejoined at the centromere and that formed a trivalent (19ii+ liii) in about 83% of PMC. Most trivalents (approximately 92%) aligned at metaphase in a 'V' configuration(alternate disjunction) while the rest aligned in linear 'I'(adjacent disjunction) or ambiguous 'L' configurations. Genetic analysis of a testcross of these 'fusion monosomics' showed that this preferential co-orientation of the trivalent influenced the assortment of the chromosome arms involved. Loci that were located in the hemizygous ends of the 'V' trivalent showed strong quasi-linkage in that most ovules from the female testcross carried relevant DNA markers either from both standard chromosomes or from neither. This shows that, in most cases, the two standard chromosomes assorted to the same pole while the fused monosome segregated to the opposite pole. For heterozygous loci (present both on the fusion monosome and the standard chromosomes) assortment was either independent or showed partial linkage to the hemizygous arm depending on the reported recombination distance from centromere. Marker assortment was further distorted in male testcrosses and in doubled haploids (made from the fusion monosomics by the maize method) by the strong selective advantage of pollen or haploids that inherited the standard chromosomes rather than the deficiencies. This genetic data shows that under the combined influence of alternate disjunction and natural selection, progeny of fusion monosomics will revert to the standard disomic arrangement, fixing the gene content of both hemizygous arms in the process. Thus, any pair of genes could be targeted for joint fixation by isolating the fusion monosome that will link them temporarily in a segregating population.

Chromosome Mapping↗
PubMed1993

Variance components for statistical genetics: applications in medical research to characteristics related to human diseases and health.

RA Fisher introduced variance components in 1918. He synthesized Mendelian inheritance with Darwin's theory of evolution by showing that the genetic variance of a continuous trait could be decomposed into additive and non-additive components. The model can be extended to include environmental factors, interactions, covariation, and non-random mating. Identifiability depends critically on design. Methods of analysis include modelling the mean squares from a fixed effects analysis of variance, and covariance structure modelling, which can be extended to multivariate traits and has been used to study ordinal traits by reference to postulated, unmeasured, latent 'liabilities'. These methods operate on dependent observations within independent groups of the same size and structure, and therefore require balanced designs ('regular' pedigrees). A multivariate normal model handles data in its generic form, utilizes data efficiently from all members of pedigrees of unequal size or varying structure, accommodates individuals missing at random, and allows flexible modelling with tests of distributional assumptions and fit. Most analytical methods use least squares or maximum likelihood under normal theory. Robust methods, scale transformation, ascertainment, path diagrams and correlational path models (popular in behavioural genetics through addressing nonrandom mating and social interactions), 'heritability', and the contribution and limitations of statistical modelling to the 'nature-nurture' debate, are discussed.

Genetic Diseases, Inborn↗
PubMed1987

Mismatch repair during pneumococcal transformation of small deletions produced by site-directed mutagenesis.

The genetic behaviour of short non-homologous regions has been studied during transformation of Streptococcus pneumoniae. Amethopterin-resistant mutants belonging to the amiA locus were used for these investigations. Five mutants deleted for 1-5 bp were obtained by oligonucleotide-directed mutagenesis. Their efficiency of transformation was measured using recipient strains either able to excise and repair mismatched bases (Hex+) or Hex- derivatives. Deletions or insertions of 1 and 2 bp are fully recognized by the Hex system, and are efficiently repaired whereas 3-bp deletions or insertions are only partially excised and repaired. The efficiency of repair is inversely related to the size of the non-homology. Markers with 5-bp deletions or insertions are poorly repaired and thus transform at very high frequency: similar results are obtained in reciprocal crosses. It is proposed that 1- or 2-bp deletions or insertions are included in the heteroduplex structure as transition mutations. The Hex system would detect only small deviations from the normal DNA structure.

Chromosome Deletion↗
PubMed2000

A pilot study of sibling resemblance in later life.

OBJECTIVE: Behavioural genetic studies of later life are strictly limited. We carried out a community-based pilot study of sibling resemblance with the primary aims of establishing the feasibility of such work in this population and estimating genetic influence on depression and its risk factors. METHODOLOGY: Data were collected on surviving siblings of individuals interviewed in previous phases of an epidemiological study of the elderly (the Gospel Oak survey); scales relevant to the investigation of late life depression and its risk factors were utilized. Since families tend to be geographically scattered, the interview was conducted by telephone. Comparisons were made between data relating to the siblings and those obtained on the probands. Variability in phenotypic traits and environmental measures was partitioned into between- and within-family variation, in order to distinguish familial and non-familial sources of variation. Intraclass correlations were used to estimate the strength of genetic influences on continuous measures, while pairwise concordances were calculated for dichotomous traits. RESULTS: Thirty-two siblings from 20 families were ultimately identified and interviewed. Intraclass correlations for the Depression and Dementia Diagnostic Scales and the Handicap Scale were 0, 0.27 and 0.22, respectively. Those for number of life events, number of friends in contact and number of neighbours in contact were 0.08, 0.03 and 0, respectively. Concordance for both depression caseness and dementia caseness was 0. DISCUSSION: There were difficulties carrying out this study, which are discussed. The study is the first of its kind to examine familial resemblance for the common disorders of old age. Establishing ways of engaging elderly families with research will be a challenge that future research will need to meet.

Aged↗
PubMed1998

Variation in tooth morphology of Gorilla gorilla.

Gorilla gorilla exemplifies a species that shows considerable variation in habitat, behaviour, genetic structure and morphology. This study examines variation of dental morphology in gorillas. Despite the marked size dimorphism, there are no significant shape differences between the sexes within subspecies. Differences in dental morphology, including tooth cusp proportions between the western G. g. gorilla and the eastern G. g. beringei are considerable. Although more similar to G. g. beringei than to the western G. g. gorilla, G. g. graueri also shows distinct morphological features. This indicates that the morphology of G. g. graueri is not merely intermediate, and genetic isolation between the two eastern subspecies could have had a substantial influence. Such extensive variation in dental morphology in Gorilla gorilla can be considered to be the result of an interesting combination of factors, including local dietary adaptations.

Animals↗
PubMed1997

Risk Factors for AIDS Associated Kaposi's Sarcoma. An European Multicentre Case Control Study.

EURO-SHAKS, European study on HIV associated Kaposi's sarcoma, is a BIOMED 1 project financed by the European Union (DG XII). The Spanish side of the project has been financed by FISS (Fondo de Investigaciones Sanitarias). The aims of this study are to identify possible genetic, behavioural, biological and environmental risk factors for HIV associated Kaposi's sarcoma through a multicentre case-control study. An extensive personal questionnaire, a clinical data form and blood sample is required from all participants. In addition, a cutaneous biopsy is request from KS patients. The presence of several European groups in this project implies a large and diverse sample size and will allow to correlate the behaviour, clinical and biological data in different geographical areas, and therefore study the possible transmission routes as well as the natural history of the putative causal agent of KS. One of the main objectives of EURO-SHAKS is to create a European Bank of AIDS biological samples for possible future investigations.

Journal Article↗