SummaryThe extensive use of chemical pesticides has greatly increased the mutational load on the genome of living organisms. The problems of genetic toxicology have generated more concern than any other problem because the residual inclusion of pesticides in the environment leads to a number of direct and indirect effects on the genetic material. Induced chromosomal mutations provide a reliable index of the mutagenic potential of a chemical or a physical agent. Experience has shown that the mutagenic effect of the semilethal doses of chemicals induce a of variety of structural changes in the polytene chromosomes out of which ectopic pairings are the most frequent types of aberrations. As a consequence of these points of genetic interest, the present paper deals with the incidence of ectopic pairing of the intercalary heterochromatic bands in the polytene chromosomes of those larvae of Anopheles subpictus, which were treated with LC 20 of 4 organophosphate pesticides viz. chlorpyrifos, monocrotophos, acephate and dimethoate. When compared with the data of nontreated controls the treated larvae had an elevated incidence of intercalary heterchromatic linkages in the X-chromosome and the right and left arms of autosomes 2 and 3 (2R, 2L, 3R, 3L). The results are discussed in relevance to the fact that ectopic associations are established between those heterochromatic bands which are homologous in their chemical and genetic properties. These properties are attributed to the presence of identical A : T rich nucleotide sequences resulting from gene duplications which are induced by the cellular environments altered by the pesticides.

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SummaryThe present paper deals with the meiotic studies carried out on 2 species of Sarcococca from 2 different states, Jammu and Kashmir and Himachal Pradesh of India from Western Himalyas. Both the species uniformly exist at x=14. Interestingly, inter-bivalent size difference was seen in both the species. The meiotic course was abnormal with the appearance of bridges, laggards and cytomixis leading to an overall effect on microsporogenesis in the formation of diads, triads and tetrads either with or without micronuclei. Consequent to the meiotic anomalies, pollen fertility was reduced and pollen grains of variable sizes were produced. This is first report of cytomixis in S. pruniformis and the first chromosome count with B-chromosomes (0-2 B) for Sarcococca saligna.

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