(1) However, no mutagenic effects of amitrole were observed either in the sex chromosome non-disjunction test (females reared on medium containing amitrole at 10 ppm) or in the sex-linked recessive lethal test (males reared on medium containing amitrole at 10 ppm).
(2) Meiosis is too complex to have arisen at once full blown and a stepwise scheme is proposed for its evolution, where each step is believed to have provided an immediate selective advantage: (1) The first step in this tentative sequence is the development of a haploidization process by means of a rapid series of mitotic non-disjunctions, turned on under conditions where haploidy is favored.
(3) This synchronization of dissimilar perceptions brings together disjunctive and conjunctive categories dominated by such coordinate conjunctions as "and... and", in the living diachronic discordance.
(4) Both sets of conditions lead to the induction of mutation to antibiotic resistance, mitotic gene conversion, crossing-over and mitotic chromosomal non-disjunction.
(5) Such presynaptic activity was still evident on nerve terminals disjuncted from the synapse by enzymatic treatment prior to incubation in the conjugate.
(6) In studies on non-disjunction, detailed genetic analysis of the induced changes is possible, and these may shed light on the mechanisms involved.
(7) It is concluded that further studies in twins are necessary to prove the not yet solved problems of non-disjunction and double ovulation.
(8) By the same test technique, primary non-disjunction and chromosome loss, the M-type was studied in the eight sub-lines.
(9) The possible assoication between altered sequence of centromere disision and non-disjunction needs further confirmation.
(10) Analysis of the segregation of a marker chromosome indicated that sister chromatid loss (1:0 segregation) and sister chromatid non-disjunction (2:0 segregation) contributed equally to chromosome missegregation.
(11) BIK1 function is required for nuclear fusion, chromosome disjunction, and nuclear segregation during mitosis.
(12) Two mutants due to gene conversion but no mutants due to non-disjunction were detected.
(13) The present study confirms the increase in meiotic errors with age of mother; moreover, increasing age of the father seems to enhance non-disjunction in spermatogenesis.
(14) Such regions, termed "Disjunction Regulator Regions" (DRR), have been implicated in the regulation of X-chromosome segregation (Goldstein, P., The synaptonemal complexes of Caenorhabditis elegans: Pachytene karyotype analysis of the Dp 1 mutant and disjunction regulator regions.
(15) As genetic endpoints dominant lethality, chromosome aberrations (detachments) and non-disjunction were studied.
(16) This suggested that the white, cycloheximide resistant, leucine requiring colonies arose by mitotic non-disjunction and not only by two coincident mitotic crossing over events.
(17) Since in the trisomic cell line of the father and the son the extra chromosome 21 seems to be the same, a predisposition toward mitotic errors (non-disjunction or anaphase lagging) may be postulated, leading to the recurrent gain or loss of a specific chromosome 21.
(18) A review of the reproductive histories of five cases with trisomy 9pter yields 9q21 or 22 indicate that the balanced translocation mothers of these infants may have as high as a 23% chance of producing a chromosomally unbalanced offspring due to 3:1 disjunction.
(19) The frequency of satellite association of two different acrocentric variants in two trisomic mongols was studied taking in consideration the possible relationship of these chromosomes in the etiology of non-disjunction events.
(20) These observations indicate a high degree of mitotic instability and thus raise the question of the effect of premature centromeric disjunction on mitotic instability of dicentric chromosomes.