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M H Ross

Publications and source records attributed to M H Ross.

101 records · Page 6Linked to original sources
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Two new reciprocal translocations in the German cockroach. Cytology and genetics of T(3;12) and T(7;12).

Two new reciprocal translocations in the German cockroach have been analyzed. They were identified cytologically to be T(3;12) and T(7;12). Linkage studies showed that groups XI, IX, and IV are on chromosomes 12, 3, and 7, respectively, and clearly demonstrated sex differences in recombination. Each of these chromosomes have distinctive morphological features that facilitate their identification, and permit breakpoint and centromere localization. A sex difference in fecundity is associated with T(7;12), but not T(3;12). About 40 percent mortality occurred when T(3;12) males or females and T(7;12) females were outcrossed. Outcrossing T(7;12) males produced the expected 50 percent mortality. Cell counts at metaphase I revealed that T(3;12) males exhibit directed segregation, while T(7;12) males do not. Tests for homozygosity indicated that the T(7;12) homozygote is viable. A map of chromosome 12 is presented showing the tentative placement of linkage group XI with respect to interchange breakpoints and chromosome morphology. The results are discussed in relation to possible sex differences in chiasma localization.

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Synthesis and properties of a double translocation heterozygote involving a stable ring-of-six interchange in the German cockroach.

The synthesis and properties of a new double translocation heterozygote in B germanica, combining T (8;9) with the progressive interchange T (4;5;10), are described. Competitiveness and sterility data indicate that males are promising candidates for a "field" experiment in genetic control of a cockroach. Sterility from genetic load and embryonic trapping is complete. Disjunction properties of the parental interchanges are similar to those found in cells of the double males, but chiasma frequency of the interchanged chromosomes is increased. Evidence of a possible relationship between chiasma formation and disjunction type is discussed.

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Differential effects of duplication-deficiency gametes from T (3;12) on embryonic development in the German cockroach.

Differential embryonic development, as seen within egg cases of the German cockroach, serves to distinguish matings of interchange heterozygotes from those of wild type. In T (3;12), one group of fertilized eggs ceases development during stage I of embryonic development; a second group, during stage VII. The frequency of the two groups correlates closely with that of adjacent-1 vs adjacent-2 disjunction. It also does not differ significantly from the expected frequency if zygotes fertilized by one of the two types of adjacent-1 gametes reach a more advanced stage of development than those of the other three types of duplication-deficiency gametes. The absence of a sex difference in the stages of embryonic death indicates that it makes little difference whether aneuploid gametes are of maternal or paternal origin.

Animals↗