Monofactorial Inheritance Research Articles

Resistance in the German cockroach (Orthoptera: Blattellidae): the inheritance of diazinon resistance and cross resistance.

Reciprocal crosses were performed between a susceptible strain of Blattella germanica (L.) and a diazinonresistant strain which exhibited cross resistance to propoxur, DDT, pyrethrins, and lindane. The progeny of these reciprocal crosses were tested for resistance to all 5 insecticides. All factors conferring resistance in the resistant strain were autosomal in origin, the gene (or genes) conferring resistance to diazinon and propoxur was recessive in nature, and the gene (or genes) conferring cross resistance to DDT, pyrethrins, and lindane exhibited incomplete dominance. Monofactorial inheritance of resistance to diazinon and propoxur appeared to be more probable than multifactorial inheritance. Propoxur resistance may be attributed to a pleiotropic effect of the diazinon resistance gene. Although cross resistance to DDT, pyrethrins, and lindane also may be due to a pleiotropic effect of the diazinon-resistance gene, the possibility of a 2nd genetic system conferring resistance to these 3 insecticides cannot be excluded.

Modes of inheritance of errors of refraction.

Eighteen families in which both parents had refractions within the range of +4·0 D to −4·0 D and axial lengths seen in emmetropia (22·3-26·0 mm) showed coefficients of correlation of the order 0·5 indicative of polygenic inheritance. Such coefficients were seen for axial length (0·407) and for the cornea (0·487), but not for the lens (which is known to be yoked to the axial length). No such coefficients were seen in 19 families in which one of the parents had axial length outside the emmetropic range (nine families with long axes and 10 with short axes). The pattern of polygenic inheritance for emmetropia (completely correlated optical components) and errors of refraction up to 4·0 D (inadequately correlated components: correlation ametropia) follows that seen in stature and other measurable characters. In contrast the high refractive errors with their abnormal axial lengths (component ametropia) are—like the extremes in stature—pathological anomalies with monofactorial inheritance.

Monofactorial inheritance of early sexual receptivity in the mosquito, Aedes atropalpus

Summary 1. Aedes atropalpus , a rockpool breeding mosquito, shows at least two distinct behaviour types with regard to the time of onset of receptivity to insemination. 2. The autogenous strain shows an early onset of receptivity with a mean insemination time of 38 hr. The anautogenous strain shows a prolonged refractory period with a mean insemination time of 120 hr (5 days). 3. Analysis of hybrids and backcrosses indicate that early receptivity is under the control of a single, autosoma, semi-dominant gene. 4. The sexual behaviour of the two strains appears to differ as a result of differential rates of hormone production by the corpora allata. The autogenous strain, with a more rapid rate of hormone production and a consequently high juvenile hormone titre soon after emergence, becomes receptive early. The anautogenous strain with a slower rate of hormone production exhibits a significantly delayed receptivity. The hybrids are intermediate but more closely resemble the autogenous line. 5. Application of a juvenile hormone analogue to the anautogenous strain, homozygous for late receptivity, produced sexually precocious females which were inseminated as early as autogenous strain females.

245. Note: Statistical Tests of Hypotheses Concerning the Degree of Dominance in Monofactorial Inheritance

245. Note: Statistical Tests of Hypotheses Concerning the Degree of Dominance in Monofactorial Inheritance

Inheritance of dieldrin resistance in the larvae of Anopheles albimanus Wiedemann.

Summary and ConclusionsFollowing continued adult selection for dieldrin resistance of the El Salvador strain (RR) of Anopheles albimanus, F1, F2, and backcross progenies were produced by a method of sib-mating. The source of the homosygous susceptible mosquitoes was a colony of A. albimanus from Panama (SS). Larval progenies from individual females were tested for survival following 24 hours of exposure to 0.01 or 0.1 ppm dieldrin suspensions.The 0.01 ppm dosage killed all SS, but not the SR/RS or RR larvae. The 0.1 ppm dosage killed SS and about 88% of the SR/RS larvae, but none of the RR larvae.The mortalities in test crosses showed close agreement with those expected on the basis of monofactorial inheritance of dieldrin resistance. The results also are in agreement with Davidson's conclusion that dieldrin resistance in A. albimanus larvae is “semi-dominant.”

Genetik der Ataxie - Teleangiectasie

SUMMARYThe syndrome of ataxia-telangiectasia was studied from a genetic standpoint on a material consisting of 7 original cases from four families, and of 31 cases from the literature. A cytogenetic analysis in one patient showed the normal diploid chromosome number, while the application of Brugger's test showed a random distribution of affected members in the investigated sibships. The observed frequency of affected individuals corresponds to the one to be expected, assuming a recessive monofactorial inheritance of the syndrome. Considering the small number of consanguineous marriages observed between parents of affected individuals, the conclusion can be drawn that ataxia-telangiectasia is not so rare a condition as it is generally assumed. The responsible gene shows a pleiotropic and lethal effect.

Inheritance of dieldrin-resistance in Cimex lectularius L. and Pediculus h. humanus L

The mode of inheritance of dieldrin-resistance in Cimex lectularius L. and Pediculus h. humanus L. was investigated. The method involved the determination of dosage/mortality regression lines by exposing batches of insects to a range of dieldrin concentrations. Reciprocal crosses were made between normal (N) and resistant (R) strains of each insect, and the F1 and F2 progeny were examined for susceptibility levels over a wide range of concentrations of dieldrin. Back-crosses were made from the F1 generation to N and R strains, and the progeny were examined in the same way. In some cases, further back-crosses were made after elimination of susceptible individuals from the progeny of the first back-cross.All the results with C. lectularius were consistent with monofactorial inheritance of dieldrin-resistance through a gene of intermediate dominance. With P. h. humanus, the results were complicated by an apparent maternal effect which caused the F1 and F2 generations from a N ♀ × R ♂ cross to be less resistant than those from a R ♀ × N ♂ cross. In general, however, the results indicated genetic segregation consistent with the same type of monofactorial inheritance as that found in C. lectularius.

Dieldrin-resistance in a strain of Aedes aegypti (L.) from Puerto Rico

The cross-resistance characteristics of a dieldrin-resistant strain of Aedes aegypti (L.) from Puerto Rico were investigated by comparative tests on the adults of this and of a normal strain, using various insecticides. A resistance spectrum typical of that associated with resistance to BHC/dieldrin in other insects was revealed, characterised by slight or negligible cross-resistance to DDT, malathion and diazinon.The mode of inheritance of dieldrin-resistance was studied by determining resistance levels in the progeny of direct crosses of the resistant and normal strains and of back-crosses. The F1 generation of the direct cross was of intermediate resistance, and the F1 generation showed 1:2:1 segregation into normal, intermediate and resistant individuals. Both back-crosses showed 1:1 segregation into susceptible and intermediate individuals when the back-cross was to the susceptible parent, or into intermediate and resistant individuals when it was to the resistant parent, and these results were confirmed when one genotype was eliminated and the back-cross was repeated. These results indicate monofactorial inheritance of an autosomal gene with intermediate dominance, which is typical of the BHC/dieldrin type of resistance.

Heterosis Effects in Crinkled Leal. Heterozygotes in Gossypium arboreum L.

The inheritance of crinkled leaf '-a new abnormal mutant spotted as a rogue in the seventh generation of an inter-racial cross in G. arboreum L. viz. indicum s cernuum was reported carlier (Balasubrahmanyan and Santhanam, 1951). This type which was characterised by abnormal leaf crinkles, gave monofactorial inheritance in crosses with normal-leaved parents. The F.1 exhibited partial dominance for leaf crinkling with intermediate grades of crinkled leaves and the F.2 segregated in the ratio of. 1:2:1 respectively for normal, F. 1 and crinkled phenotypes. Both the parental classes bred true in the F. 3 while the intermediates' again threw out the three phenotypes in the ratio of 1:2:1. It was sought to study heterosis effects, if any, in a segregating population drawn from the crinkled leaf crosses, as the three geno- types were morphologically distinguishable here.. In wheat, Granhall (1949) utilised a similar advantage in recognising heterozygous half- bearded plants in a population for the beardness factor and found that the heterozygotes in the F.2 were on an average more, vigorous than the beardless' and bearded', parental class of segregates.