Backcross Males Research Articles

The inheritance of aggressiveness in the convict cichlid fish, Cichlasoma nigrofasciatum (Pisces: Cichlidae)

Intraspecific comparisons in aggression were made between X-irradiated (2 × 500 R) ancestors and untreated control animals. Bites delivered to sub-adult conspecifics were counted to measure aggressiveness. When compared with corresponding controls, a significant reduction in male aggressiveness was found in the post-irradiation F 1 generation. A greater variation in bites delivered occurred among the F 2 post-irradiation generations than among the control equivalents. Three distinct back-cross generations were obtained as follows: a single F 1 female from the irradiated line was mated to (a) her high aggressive (I-A) and (b) her low aggressive (I-NA) F 2 son; a F 1 control female was mated to her low aggressive F 2 son. In the back-cross generations, both I-A and C-NA males were more aggressive than I-NA males. No differences were found between I-A and C-NA back-cross males. The findings are discussed in terms of a two-factor model based on Mendelian laws.

Investigation of genetic factors influencing duration of copulation in ‘eastern’ and ‘western’ Drosophila athabasca

Observations of mating behaviour were made on ‘eastern’ and ‘western’ Drosophila athabasca and on flies of mixed genetic background. Duration of copulation in mixed combinations of D. athabasca is determined by the male. In F 1 males the source of X-chromosome, whether eastern or western, partly determined duration of copulation. However, durations of copulation of backcross males suggest autosomal influence, in that males derived from an eastern backcross demonstrate significantly shorter durations than males derived from a western backcross. In addition, durations of copulation from F 2 combinations exhibit greater variance than the F 1 and thereby represent evidence of F 2 segregation.

Gonenkonkurrenz bei Oenothera unter dem Einflu\ eines gametophytisch wirksamen Gens in der ersten Koppelungsgruppe sowie ein Modell für die Untersuchung verzweigter Koppelungsgruppen

The progeny ratios obtained in male backcrosses of Oenothera hybrids to the complexes hookeri and flavens (identified by two marker genes and by the translocation break) showed statistically significant differences from Mendelian expectations.Presence of a gametophytic gene in the first linkage group is proposed. Its alleles ga (+) and ga (-) are thought to control development of the male gametophytes in such a manner that pollen grains carrying the different ga alleles and developing in a heterozygous female plant, will fertilize the female gamete with different average frequencies.A series of genetic models is developed, all taking into account the relative probability of the alleles ga (+) and ga (-) to function in fertilization, the probability of crossing over between the gene loci studied, and the branched configuration of the linkage group, due to the presence of the translocation.Based on these models, the relationships between the relative frequencies of the different classes of gametes are predicted for several theoretically possible arrangements of the genes within the linkage group.The models have general application for the localization of gametophytic genes and for the localization of genes in branched linkage groups.It turns out to be impossible to give an estimate for the disadvantage of ga (-) as compared to ga (+) from the backcross data alone. The empirical data permit only a combined estimate of the probabilities of fertilization by ga (-) and of crossing over between Ga and the locus of the marker gene.Comparison between the empirical data and the model makes it possible to determine the location of the marker loci and the locus of Ga with respect to one another. A branched linkage group appears most likely, but a linear arrangement in two chromosome arms cannot be ruled out.The observed cross-over values, and consequently, the map distances between the genes studied, are highly variable, both in different hybrids and in the progeny of a single hybrid.

Biochemical genetics of house fly resistance to carbamate insecticide chemicals.

One resistant strain (RHokota) and 2 susceptible multi-chromosomal marker strains (S2356and S2450) of house flies, Musca domestica L., were used for genetic analyses with the F1 male backcross experimental design for determining linkage groups. Genetic analyses were made as follows: (1) resistance to Baygon® ( O -isopropoxyphenyl methylcarbamate) in the presence and in the absence of the synergist piperonyl butoxide; (2) Baygon metabolism in living flies; (3) Baygon metabolism by the fly abdomen enzyme-reduced nicotinamide-adenine dinucleotide phosphate (NADPH2) system; (4) resistance to Matacil® [4-(dimethylamino)- m -tolyl methylcarbamate]; (5) Matacil metabolism by the fly abdomen enzyme-NADPH2 system. Each of these comparisons showed the importance of the 5th chromosomal effect in conferring both high carbamate resistance and high activity for microsomal oxidizes involved in metabolism by ring hydroxylation and attack on N -methyl and O -alkyl groups. The 3rd chromosome is secondary in importance to the 5th chromosome in each of the above comparisons, while the 2nd chromosome is also involved in the resistance but not in the enzyme activity. Piperonyl butoxide minimizes the importance of the 5th chromosome in conferring Baygon resistance. Differences in penetration rates do not contribute materially either to the resistance or synergistic effects. Detoxification reactions involving the microsome-NADPH 2 system, which are controlled by the 5th chromosomal gene (s), are important in the mechanism of resistance to carbamate insecticide chemicals; they may also be important with other types of insecticide chemicals which are metabolized by this system and to which resistance is conferred by 5th chromosomal factors.

INTERSPECIFIC HYBRIDS AND SPECIATION IN THE GENUS ACHETA (ORTHOPTERA, GRYLLIDAE)

Acheta rubens produced interspecific hybrids with both the "northern spring species" (NSS) and assimilis in the laboratory, but not with pennsylvanicus; assimilis crossed with both rubens and pennsylvanicus but not with NSS; NSS crossed only with rubens; pennsylvanicus crossed only with assimilis. All other attempts to cross the four species failed. Over 2500 assimilis × rubens hybrids were produced within [Formula: see text] months; less than 1000 rubens × NSS hybrids were produced over about 18 months. The developmental rate of males carrying rubens X chromosomes was extremely slow in both rubens × assimilis and rubens × NSS hybrids; hybrid males carrying either assimilis or NSS X chromosomes, and all hybrid females, developed at normal rates, or at rates intermediate between those of the parental species. The songs of certain hybrid males were intermediate between those of the parental species in certain features but resembled the song of one parental species in other features. Fertile backcross males and females were produced by rubens × NSS hybrid females but the viability and fertility of the offspring of these specimens were abnormally low; both backcross and F2 nymphs have been produced by rubens × assimilis hybrids. The incubation periods of hybrid eggs laid by pennsylvanicus females were less than half those of normal pennsylvanicus eggs at the same temperature.

Observations on Two Cases of Interspecific Hybridization with Drosophila athabasca

Drosophila athabasca males will inseminate females of the similar species D. affinis and D. algonquin, and both these crosses lead to hybrid production. D. athabasca females have been inseminated by D. affinis males, but hybrids have not been produced. Female hybrids between algonquin and athabasca are fertile and have been crossed to algonquin males. Sex comb size, which differs between these species (algonquin has large sex combs, athabasca small ones) has been studied in hybrid and backcross males from some of the crosses. Although the frequency of affinis females inseminated by athabasca males is fairly high, the number of hybrids produced by this combination is very low. Neither sex of the hybrids appears to be fertile.

Pollen Tube Growth and Control of Gametophytic Selection in Cocklebur, a 25-Chromosome Datura

1. Pollen tube distributions were plotted from 12-, 16-, and 18-hour tests, using the pollen of the primary (2n + 1) Cocklebur germinated and grown on the pistils of 2n plants. These tests were compared with similar tests of pollen tube growth of normal plants in line 1a. 2. Further evidence is given from the results of ordinary male back-crosses of Wedge to four lines, indicating that the latter is a secondary (2n + 1) type related to Cocklebur. Pollen tube distributions obtained from the pollen of Wedge are also plotted. 3. The pollen tube distribution curves indicate that Cocklebur may be transmitted through the pollen under conditions in which the processes of gametophytic selection are controlled experimentally. Likewise, the distribution curves indicate that Wedge may not be transmitted through the pollen in line 1A. 4. The correctness of the interpretations gained from pollen tube distribution curves was tested genetically in the case of Cocklebur, by combining three other experimental methods: the effects of restricted pollinations; the effects of excision of styles; and the separation of the seeds in the lower half of seed capsules from those in the upper half. Results from all experimental methods confirmed the interpretations gained from a study of pollen tube distribution curves. 5. The various methods which have been used by investigators at different times in a study of the effects of gametophytic selection are briefly discussed and compared. 6. The pollen tube distribution curves obtained from suitable tests enable us to recognize processes of gametophytic selection, and have the further advantage of enabling us to distinguish between at least five different conditions, all of which may lead to the complete or partial elimination of some of the classes of male gametophytes, resulting in modified ratios in the progeny. 7. The processes of gametophytic selection involved in the pollen transmission of Cocklebur may be controlled through a wide range. A threefold increase may be obtained by restricted pollinations, and a further increase, up to 65 per cent Cocklebur plants, may be obtained in a progeny by selecting the seeds to be planted from the lower parts of seed capsules, while complete non-transmission of Cocklebur may be obtained by properly timed excisions of styles.