Morphological and chromosomal descriptions of new species in the Anopheles subpictus complex

Abstract. Anopheles subpictus Grassi is shown to comprise four reproductively distinct species, designated A, B, C and D, occurring sympatrically in villages of Pondicherry, southeast India.
Adult females were reared individually from wild larvae and examined for their morphological and chromosomal characters. Paracentric fixed inversions on the X-chromosome serve to distinguish the species cytogenetically, with no inversion heterozygotes (i.e. no interspecific hybrids) among totals of 717 species A (X+^a,+^b), 1863 species B (Xa, b), 869 species C (Xa,+^b) and 1365 species D (X +^a,b) identified.
Morphologically, diagnostic characters for each of the four species are seen in the egg float ridge number, larval mesothoracic seta 4, pupal seta 7-1 and the palpi of female adults. Species A. C and D immatures inhabit freshwater, whereas the malaria vector species B breeds in saltwater and was found only in coastal villages.     

The allelic isozymes of hexose-6-phosphate dehydrogenase isolated from Fundulus heteroclitus: physical characteristics and kinetic properties

Hexose-6-phosphate dehydrogenase (H6PDH-A2; beta-D-glucose:NAD(P)+oxido-reductase; E.C. 1.1.1.47) of the teleost Fundulus heteroclitus (L.)shows clinal allelic variation along the east coast of North America. Threeof the major allelic isozymes have been purified and compared for nativemolecular weight, subunit molecular weight, isoelectric point, thermalstability, and steady-state kinetic properties (pH 8.0 and 25 degrees C).Significant differences were found among the allelic isozymes forisoelectric point, thermal stability, and some kinetic parameters. Thepredominant allelic isozyme in northern populations (H6PDH-AcAc) was foundto be more sensitive to heat denaturation than were the predominanthomozygous allelic isozymes isolated from southern populations (H6PDH-AaAaand H6PDH-AbAb). The H6PDH-AcAc allelic isozyme had both a significantlygreater Km for glucose-6-phosphate than did either of the southernphenotypes and a significantly greater Km for NADP+ and Ki of NAD+ than didone of the southern phenotypes (H6PDH-AaAa). While the allelic isozymes arefunctionally nonequivalent, it is not yet known whether these differencesare reflected at higher levels of biological organization.     

Interchromosomal recombination is suppressed in mammalian somatic cells.

Homologous recombination occurs intrachromosomally as well as interchromosomally, both in mitotic (somatic) cells as well as meiotically in the germline. These different processes can serve very different purposes in maintaining the integrity of the organism and in enhancing diversity in the species. As shown here, comparison of the frequencies of intra- and interchromosomal recombination in meiotic and mitotic cells of both mouse and yeast argues that interchromosomal recombination is particularly low in mitotic cells of metazoan organisms. This result in turn suggests that the recombination machinery of metazoa might be organized to avoid the deleterious effects of homozygotization in somatic cells while still deriving the benefits of species diversification and of DNA repair.