The genetic determination of resistance to the sterility-producing genetic elements called P factors was studied in a strain characterized as neutral (Q) in the P-M system of hybrid dysgenesis. Sixteen lines were synthesized, representing all possible homozygous combinations of the three major chromosomes and differing maternal cytoplasms of an original resistant (Q) and susceptible (M) strain....

Chromosome counts and karyotypes of two species of Chrysolaena H. Robinson 1988 are presented in this paper. Mitotic analysis revealed that both taxa have x=10, a basic chromosome number considered characteristic of the genus. The chromosome number and the karyotype of Chrysolaena cristobaliana are reported for the first time, as well as a new cytotype and the karyotype of Chrysolaena sceptrum....

Valeriana jatamansi, a medicinally important species of the family Valerianaceae, has been cytologically studied in different geographical areas of North-Western Himalayan region of India. The tetraploid cytotype with chromosome numbers 2n=32 is in conformity with the earlier reports of the species from different parts of the world. An octoploid cytotype (2n=64) makes a new addition for the spe...

Three populations of Drosophila melanogaster from northern California were surveyed for the ability to produce and resist gonadal dysgenesis in the P-M system of hybrid dysgenesis. Males from all three populations produced low to moderate levels of gonadal dysgenesis in crosses to Oregon-R M females. Most females had the P cytotype, but the M cytotype occurred occasionally. The three population...

The distribution of cytotypes in mixed-ploidy species is crucial for evaluating ecological processes involved in the establishment and evolution of polyploid taxa. Here, we use flow cytometry and chromosome counts to explore cytotype diversity and distributions within a tetraploid-octoploid contact zone. We then use niche modelling and ploidy seed screening to assess the roles of niche differen...

Using PCR and sequencing we have demonstrated the presence of P elements in genomes of Drosophila melanogaster from natural populations of Ukraine. The degree of gonadal reduction revealed indirectly indicates low or, in some cases, zero activity of the mobile element in the inspected natural populations of Drosophila. All studied populations have been found to represent the M’ cytotype. In thi...

Previous studies have shown that telomeric P elements inserted at the left end of the X chromosome are anchors of the P cytotype, the maternally inherited state that regulates P-element activity in the germ line of Drosophila melanogaster. This regulation is mediated by small RNAs that associate with the Piwi family of proteins (piRNAs). We extend the analysis of cytotype regulation by studying...

The two interacting components of the P-M system of hybrid dysgenesis are chromosomally associated elements called P factors and a susceptible cytoplasmic state referred to as M cytotype. Previous experiments have indicated that P factors are a family of multiple-copy transposable genetic elements dispersed throughout the genome of P strains but absent in long-established M strains.-Evidence is...

Karyotypes of seventeen Hoplias malabaricus specimens, collected in the fish culture station of UNOPAR (University of Northern Paraná), were analyzed. The station is in the Claro River system in the Tibagi River basin. Two distinct and coexistent karyotype forms (cytotypes) were identified, comprising either 42 chromosomes (cytotype A) or 40 chromosomes (cytotype C), both presenting metacentric...

The material identified as Kiefferulus tendipediformis on the basis of the larval morphology consisted of two cytogenetically distinct species, which we called cytotype 1 (2n=8) (Bulgaria) and cytotype 2 (2n=6) (Poland). The karyotype and external morphology (larva, pupa and imago males) of Kiefferulus tendipediformis from pond on mine spoils in the Olkusz region with Zn-Pb ore deposits (Southe...