• S. Gershenson

      Articles written in Journal of Genetics

    • Studies on the genetically inert region of theX-chromosome ofDrosophila - I. Behaviour of anX-chromosome deficient for a part of its inert region

      S. Gershenson

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      1. As a result of crossing-over between two differently invertedX-chromosomes anX-chromosome was obtained with a deficiency for a part of its genetically inert region.

      2. In theXY males carrying this chromosome, theX andY-chromosomes synapse only in 61·4 per cent. of cases. Each of the unsynapsed chromosomes is lost during disjunction approximately in one-fourth of the cases, not reaching either of the daughter nuclei.

      3.XYY males carrying this chromosome produce gametes almost exclusively of theXY andY types.

      4. The case studied appears to confirm the views of Muller and Painter concerning the homology of the inert part of theX-chromosome with theY-chromosome, and supports the opinion that few or no gene mutations can at present arise in theY-chromosome (except those of the genebb).

    • The mechanism of non-disjunction in theClB stock ofDrosophila melanogaster

      S. Gershenson

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      1.XXY females heterozygous for theClB chromosome give among their offspring about 35 per cent. of secondary exceptions. The percentage of secondary exceptions is equal in the male and female offspring. TheY-chromosome disjoins from theClB chromosome and from the normalX-chromosome with equal frequency.

      2. InClB females crossing-over between theX-chromosomes is greatly inhibited. The percentage of cross-overX-chromosomes carried by the gametes ofXX-ClB females is equal to that ofXXY-ClB females, indicating the correctness of Anderson’s conception of the mechanism of secondary non-disjunction.

      3.XX-ClB females give among their offspring about 0·35 per cent. of primary exceptions. The comparison of the number of non-cross-overX-chromosomes produced by such females, with the frequency of non-disjunction in their offspring shows that the mechanism of chromosome disjunction in the male and femaleDrosophila is essentially similar, and speaks against Darlington’s views concerning the relation between crossing-over and the disjunction of chromosomes.

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