Sex Drive
Mostrando 25-36 de 41 artigos, teses e dissertações.
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25. Multiple Meiotic Drive Systems in the DROSOPHILA MELANOGASTER Male
The behaviour of two "meiotic drive" systems, Segregation-Distorter (SD) and the sex chromosome sc4sc8 has been examined in the same meiocyte. It has been found that the two systems interact in a specific way. When the distorting effects of SD and sc4sc8 are against each other, there is no detectable interaction. Each system is apparently oblivious to the pr
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26. Evidence for Extensive Genetic Differentiation between the Sex-Ratio and the Standard Arrangement of DROSOPHILA PSEUDOOBSCURA and D. PERSIMILIS and Identification of Hybrid Sterility Factors
This study deals with sex-ratio genes tightly linked within the Sex-Ratio inversion. By taking advantage of the fact that the Sex-Ratio chromosome of Drosophila persimilis [SR(B)] is homosequential to the Standard chromosome of D. pseudoobscura [ST(A)], we carried out two reciprocal introgression experiments. Individual segments of SR(B) or ST(A) were introg
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27. Components of Selection in X Chromosome Lines of DROSOPHILA MELANOGASTER: Sex Ratio Modification by Meiotic Drive and Viability Selection
Selection coefficients and segregation parameters have been estimated in 18 randomly chosen lines carrying wild X chromosomes on the cn bw genetic background. Each line was studied in replicated crosses of four types, with approximately 100 replications per line per cross. Crosses in which male X chromosomes differed exhibited significant sex ratio heteroge
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28. Preliminary Characterization of "Sex Ratio" and Rediscovery and Reinterpretation of "Male Sex Ratio" in DROSOPHILA AFFINIS
In D. affinis "sex ratio" (sr), a form of meiotic drive characterized by the production of mostly or only female progeny by certain males, is associated with two different X chromosome sequences, XS-I XL-II and XS-II XL-IV. The behavior of the two sequences differed, depending on the Y chromosome constitution, being either YL or 0. Males with sequence XS-II
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29. Parkinson's disease and driving ability.
There is no guidance available for clinicians who have to decide on the fitness to drive of patients who have Parkinson's disease (PD). A computerised driving simulator was used to examine the effect of PD on driving ability. Ten drivers with idiopathic PD were tested as well as 10 age and sex-matched healthy drivers and four PD drivers who were no longer dr
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30. Meiosis in Male DROSOPHILA MELANOGASTER I. Isolation and Characterization of Meiotic Mutants Affecting Second Chromosome Disjunction
Two second chromosome, EMS-induced, meiotic mutants which cause an increase in second chromosome nondisjunction are described. The first mutant is recessive and causes an increase in second chromosome nondisjunction in both males and females. It causes no increase in nondisjunction of the sex chromosomes in either sex, nor of the third chromosome in females.
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31. Integration of a B chromosome into the A genome of a wasp.
B chromosomes are genome symbionts, the presence of which in many eukaryote species is explained, in most cases, by their violation of Mendelian rules, usually based on meiotic or mitotic instability, leading to their accumulation in the germ line (drive). However, B chromosome integration into the genome as a regular member of the chromosome set should impl
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32. Breathing pattern and central ventilatory drive in mild and moderate generalised myasthenia gravis.
BACKGROUND--Myasthenia gravis is a specific autoimmune disease characterised by weakness and fatigue. Respiratory muscle weakness has been studied using the determination of maximal respiratory pressures, but the response of respiratory centres is not well characterised. This study was undertaken to determine the breathing pattern and the central ventilatory
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33. Genetic Analysis of Sex Chromosomal Meiotic Mutants in DROSOPHILA MELANOGASTER
A total of 209 ethyl methanesulfonate-treated X chromosomes were screened for meiotic mutants that either (1) increased sex or fourth chromosome nondisjunction at either meiotic division in males; (2) allowed recombination in such males; (3) increased nondisjunction of the X chromosome at either meiotic division in females; or (4) caused such females, when m
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34. Sex, bowers and brains.
Inter- and intraspecific variations in the sizes of specific avian brain regions correspond to the complexity of the behaviour that they govern. However, no study has demonstrated a relationship between gross brain size and behavioural complexity, a hypothesis that has been proposed to explain the unusually large human brain. I show, using X-rays of museum s
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35. How does selection reconcile individual advantage with the good of the group?
An individual's advantage often conflicts with the good of its group, as when an allele spreads by meiotic drive through a population whose death rate it increases, or when an asexual genotype derives immediate advantage at the expense of future adaptability. We show how selection within populations may reconcile individual and group advantage, as in the evo
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36. Cytogenetic Analysis of a Segment of the Y Chromosome of DROSOPHILA MELANOGASTER
Males carrying a large deficiency in the long arm of the Y chromosome known to delete the fertility gene kl-2 are sterile and exhibit a complex phenotype: (1) First metaphase chromosomes are irregular in outline and appear sticky; (2) spermatids contain micronuclei; (3) the nebenkerns of the spermatids are nonuniform in size; (4) a high molecular weight pro