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Biomedical subjects

T A Markow

Publications and source records attributed to T A Markow.

18 recordsLinked to original sources
PubMed1992

Human handedness and the concept of developmental stability.

A model is proposed to explain the etiology of pathological handedness. Developmental instability, caused by elevated genotypic homozygosity, environmental disturbances, or their interaction, overrides programmed laterality and handedness in the same way that it perturbs the bilaterally symmetrical expression of morphological and metric traits. The model predicts that pathological handedness should be elevated among individuals with higher than average homozygosity and individuals who have developed under unfavorable uterine environments. Suggestions are offered for specific populations in which the predictions may be tested.

Functional Laterality↗
PubMed1992

Male size, developmental stability, and mating success in natural populations of three Drosophila species.

Morphological correlates of male mating success were assessed in natural populations of three Drosophila species. Mating males in D. simulans were larger than single males but were characterized by reduced developmental stability as indicated by fluctuating asymmetry. Mating male D. pseudoobscura were no larger than single males but exhibited significantly greater developmental stability. In D. mojavensis, however, mating males were larger and they showed a similar level of fluctuating asymmetry to that observed in single males. The differences observed between species are discussed in the context of their mating systems and reproductive ecology.

Animals↗
PubMed1991

Developmental stability in hybrids between the sibling species pair, Drosophila melanogaster and Drosophila simulans.

Drosophila melanogaster and its sibling species D.simulans were hybridized in the laboratory to test the hypothesis that developmental homeostasis in hybrids between two species having no prior gene flow would be significantly reduced. Developmental stability was assessed by measuring fluctuating asymmetry for three bilateral traits: sternopleural chaetae, wing length, and fronto-orbital plus frontal chaetae. Male F1 hybrids showed no decrease in developmental stability compared to males of parental species. Female hybrids showed significant fluctuating asymmetry compared to other flies. The results are discussed with respect to ideas about coadaptation and gene flow based upon previous studies of hybrid developmental stability.

Animals↗
PubMed1989

Fluctuating dermatoglyphic asymmetry in psychotic twins.

Fluctuating asymmetry of bilateral morphological traits is the result of prenatal developmental instability and has been shown to be greater in organisms having more homozygous genotypes (aabb vs. AaBb, for example). This expected increase in fluctuating asymmetry has been found among individuals having a high degree of liability for schizophrenia, as this disorder appears to have a polygenic basis. We tested the additional prediction that the greater genetic liability for schizophrenia necessary for concordance between twins should be associated with greater fluctuating asymmetry in twin pairs in which both twins are mentally ill compared to twin pairs in which one individual is normal. Our analysis of asymmetry for finger ridge counts from fingerprints of concordant and discordant pairs of twins supports this prediction and provides additional indirect support for the roles of polygenic transmission and prenatal epigenetic vulnerability in schizophrenia.

Adult↗
PubMed1989

Dermatoglyphic fluctuating asymmetry in twins and singletons.

The influence of twinning on developmental stability was measured by comparing fluctuating asymmetry in dermatologlyphic traits in monozygotic twins, dizygotic twins, and singletons. Despite reports that twinning has been reported to influence development of traits such as birth weight and I.Q., no significant difference in fluctuating asymmetry was found between different zygotic categories.

Dermatoglyphics↗
PubMed1988

Reproductive behavior of Drosophila melanogaster and D. nigrospiracula in the field and in the laboratory.

The reproductive behaviors of two species of fruit fly, Drosophila melanogaster and D. nigrospiracula, were compared in field and laboratory populations. A number of differences were observed in the behavior of the two species in their natural habitats. D. melanogaster, which was observed on citrus, mates at its feeding site, whereas D. nigrospiracula, which is cactiphilic, mates on a non-resource-based male territory adjacent to its feeding site. In both species large male size is important for reproductive success. However, in D. melanogaster smaller males tended to be excluded from the breeding site and were therefore not among the pool of potential mates to which females were exposed. Sex ratios were biased toward females in both species, but the high frequency of female remating in D. nigrospiracula may have provided more mating opportunities for the males of this species. Field observations differed from laboratory observations, and I discuss the importance of these differences for understanding the evolution of Drosophila mating systems.

Animals↗
PubMed1987

Behavioral and sensory basis of courtship success in Drosophila melanogaster.

In Drosophila some individuals are more successful at mating than others. Reproductive fitness is strongly dependent upon the ability to recognize and compete for members of the opposite sex. Experiments were designed to answer two questions. (i) What behavioral components are characteristic or predictive of successful courtship? and (ii) How important is the information transmitted in the different sensory channels for courtship success in each sex? These questions were approached by two experimental procedures. Flies having a sensory deficiency (olfactory, auditory, or visual) competed with wild-type flies of the same sex for mates. Males were found to rely upon sensory channels different from those used by females in order to court successfully. In addition, the courtships of pairs of various genotypes were recorded and subjected to multivariate analysis. The multivariate courtship profiles deviated most widely from those of successful wild-type pairs when the male or female was unable to receive information in the sensory channel most important for successful mating by that sex. Both sequential and quantitative courtship properties were altered when one participant was deficient in ability to receive certain sensory information.

Animals↗
PubMed1979

A survey of intra- and interspecific variation for pupation height in Drosophila.

Pupation heights of various natural and laboratory populations of Drosophila melanogaster, D. simulans, and D. pseudoobscura were observed in the laboratory under conditions of continuous darkness or continuous light. Generally higher mean pupation heights were observed under conditions of darkness. D. melanogaster tended to pupate higher than the D. pseudoobscura populations, and D. pseudoobscura tended to pupate higher than D. simulans. The order of these species differences was similar whether pupation was measured in light or in darkness. Results of selection for pupation height in D. melanogaster suggest the presence of genetic variation for this character. The possibility that a relationship exists between adult and larval behaviors was explored by measuring the pupation heights of larvae from strains selected for geotactic behavior as adults, and also by measuring geotaxis of adults from strains selected for pupation height.

Animals↗
PubMed1978

Positive and negative geotaxis: sex-linked traits in Drosophila pseudoobscura.

Using a Hirsch classification maze, selection was made for positive and negative geotactic behaviors in three different strains of Drosophila pseudoobscura. Hybridization studies were then carried out with flies from the diverged strains. The geotactic scores of the parents and F1 flies indicate that both negative and positive geotactic behaviors in these strains are strongly influenced by genes in the X chromosome. Additional hybridization studies using flies from strains with similar phenotypes suggest that the diverged strains contain similar alleles and the number of loci in the X chromosomes responsible for these types of behavior is limited. The loci may be highly organized in the X chromosome.

Animals↗
PubMed1977

Effect of age and of screening pigment mutations on the phototactic behavior of Drosophila melanogaster.

Five different eye color mutations of Drosophila melanogaster have been tested for their effect on phototactic behavior. All five mutations seem to cause flies to be less photonegative than Canton-S control flies. The mutation sepia was found to produce this effect when heterozygous as well. It was also found that wild-type flies from highly photopositive and photonegative strains seem to be more photoneutral with age.

Age Factors↗
PubMed1977

Phototactic and geotactic behavior of countercurrent defective mutants of Drosophila melanogaster.

Ten behavioral mutations, originally isolated in the countercurrent fractionation device, were tested in phototaxis and geotaxis mazes. While none of the mutations caused an altered ERG, they all caused photomaze behavior to differ from that seen in Canton-S controls. Eight of the mutants showed altered geotactic behavior. There was no correlation between the kind of change in phototactic behavior and the geomaze behavior of a given mutant. Certain mutations cause flies to be more photopositive and more geonegative than Canton-S; others result in behavior that is photo- and geopositive. The results suggest that certain mutations may be affecting visual components other than the ERG while other mutations may be more centrally or generally acting.

Animals↗
PubMed1977

Genetic analysis of phototactic behavior in Drosophila simulans.

Phototaxis mazes have been employed to select photopositive and photonegative strains of Drosophila simulans. The results suggest that phototactic behavior in D. simulans, as in other Drosophila species, is a polygenic trait. Hybridization using divergent strains revealed that the genes controlling negative phototactic behavior in D. simulans are autosomal, as opposed to D. melanogaster in which negative phototactic behavior is known to be very strongly sex-linked.

Animals↗
PubMed1975

A genetic analysis of phototactic behavior in Drosophila melanogaster. II. Hybridization of divergent populations.

Artificial selection has produced populations of Drosophila melanogaster which show either positive or negative phototactic behavior. Selection was carried out in the presence of various marked multiple inversions used to suppress genetic recombination. Reciprocal hybridizations between photopositive and photonegative populations of flies have revealed the X chromosome of D. melanogaster to be important in phototactic behavior regardless of conditions which restricted genetic recombination during selection.

Animals↗
PubMed1975

A genetic analysis of phototactic behavior in Drosophila melanogaster I. Selection in the presence of inversions.

The effectiveness of selection for positive and negative phototactic behavior in populations of Drosophila melanogaster heterozygous for various multiple inversions was compared using the method of realized heritability. Selection in the presence of FM6, SM1 or TM3 alone was as effective as in populations carrying no inversions. However, the presence of FM6 and TM3 together reduced the effectiveness of selection for photopositive behavior and FM6 and SM1 and TM3 restricted the response to selection for negative phototactic behavior. The results are discussed in terms of the organization of genes influencing phototactic behavior in this species.

Animals↗