Behavior of gynandromorphs of the wasp Habrobracon juglandis.

A study was made of sex behavior for 276 gynandromorphs of the wasp Habrobracon juglandis. In general, gynandromorphs with male heads behaved like males, those with female heads behaved like females, and those with mosaic heads as either male or female or both. These observations corroborate those made by P. W. Whiting in 1932 and confirm his view that the site of sex behavior is in the brain. Correlations between sex behavior and the sex of various body structures showed clearly that sex behavior is unrelated to the thorax, abdomen and genitalia. The sex behavior of gynandromorphs does not seem to be related to the sex of the external sensors of the head but rather to the genotype of the brain.     

Influence of juvenile hormone analogues on reproductive performance in the wasp, Habrobracon juglandis.

Egg production was reduced in adult virgin Habrobracon juglandis females treated topically with either acyclic or aromatic terpenoid ether, analogues of juvenile hormone. The latter type, particularly the compound possessing a 3,4 methylenedioxyphenyl group, was most effective against the wasp. The resulting changes in fecundity were due to interference with vitellogenic activity.The 3,4 methylenedioxyphenyl analogue treatment decreased hatchability in oöcytes exposed during vitellogenesis. Embryonic death in eggs derived from these cells was typified by blocked cleavage division.The relationship between chemical structure and biological activity supports the hypothesis that juvenile hormone analogues may act in part by blocking detoxification mechanisms in treated insects. This in turn, either separately or in combination with direct analogue action, adversely affects reproduction by inhibiting processes involving RNA synthesis.     

X maternal mosaicism and genetic counseling

Among number of women having consulted for repeated miscarriages about sixty have a gonosomic mosaicism involving chromosome X for which abnormal clones (monosomy and/or excess) are always the minority. A retrospective study of the obstetrical follow up these patients have shown that 23% of them will give birth to a child with a chromosomic abnormality (21 trisomy, 13 trisomy, 45,X, 45,X/46,X iso X (q), 48,XXXX, 49 XXXXXY, del 5 p-). The hypothesis of a tendency toward non-disjunction is pushing for an prenatal diagnosis for patients with X mosaicism. However one can question about the real meaning of this abnormality regarding to the fact that the patients referred are not representative of the general population. Should interchromosomic interaction be taken for responsible? Is the risk for having a child chromosomic abnormality, especially X aneuploidy the same than for the overall population. It certainly would be rewarding to look after these different hypothesis in a multicentric collaborative study.     

Germ-line mosaicism simulates genetic heterogeneity in Wiskott-Aldrich syndrome.

The Wiskott-Aldrich syndrome (IMD2) is an X-linked recessive immunodeficiency. Initial linkage studies mapped the disease locus on the proximal short arm of the X chromosome, a localization which was further refined to the interval framed by DXS7 and DXS14. We have recently shown that a novel hypervariable locus, DXS255, is very closely linked to the disease gene and is likely to be, at present, the marker closest to the disease gene. The analysis of one family, however, displayed conflicting linkage results, as all of the informative markers situated in the Xp11-q22 region appeared to recombine with the disease locus in two "phase-known" meioses. We have shown by X-inactivation studies that the segregation of the disease through three obligate carrier females in this family originates from a grandpaternal mosaicism, which accounts for the apparent recombinations. This shows that germ-line mosaicism can simulate genetic heterogeneity in linkage studies.     

Patterns of genetic differentiation in Thamnophis and Taricha from the Pacific Northwest

Aim The co‐evolutionary interaction between the common garter snake, Thamnophis sirtalis, and the rough‐skinned newt, Taricha granulosa, takes place throughout much of the Pacific Northwest (North America). The biogeography of the Pacific Northwest has been heavily influenced by the last Pleistocene glaciation, which reached a maximum as late as 14,000 yr bp . We researched: (1) what type of population structure is present for garter snakes and newts, (2) whether the population structure of these species is consistent with a Pleistocene glaciation hypothesis, and (3) how population structure and migration possibly affect co‐evolution between these species. Location The Pacific Northwest of North America, specifically northern California, Oregon and Washington in the USA. Methods We sampled approximately 20 populations for each species from three different transects. Using microsatellite markers and tissue samples from both species, we quantified the population structure for both species. Individual‐based assignment tests were used to estimate contemporary migration rates. Results Both Th. sirtalis and Ta. granulosa exhibited little genetic differentiation among our study sites, even among those separated by large distances. Significant population structure was detected on multiple geographic scales. Differences in population structure were observed among transects and between garter snake and newt transects. Contemporary migration rate estimates indicate high levels of genetic exchange between populations. Main conclusions Prior to this study, little was known about the fine‐scale population structure of either species in this region. Patterns of population structure for garter snakes and newts reflect a shared biogeographical history affected by the Pleistocene glaciation in the Pacific Northwest. Both species apparently migrate frequently between populations, thus potentially retarding the process of adaptive co‐evolution. We find that populations from a northern coastal transect (Washington) are most likely to be locally adapted.