Many plant species contain populations with more than one polyploid cytotype, but little is known of the mechanisms maintaining several cytotypes in a population. Andropogon gerardii cytotypes were compared to evaluate different models of autopolyploid cytotype coexistence. The enneaploid (90 chromosome, 9x) cytotype was found to be larger and taller than the hexaploid (60 chromosome, 6x) cytot...

P element transposition in Drosophila is controlled by the cytotype regulatory state: in P cytotype, transposition is repressed, whereas in M cytotype, transposition can occur. P cytotype is determined by a combination of maternally inherited factors and chromosomal P elements in the zygote. Transformant strains containing single elements that encoded the 66-kD P element protein zygotically rep...

Activity of the P family of transposable elements in Drosophila melanogaster is regulated primarily by a cellular condition known as P cytotype. It has been hypothesized that P cytotype depends on a P element-encoded repressor of transposition and excision. We provide evidence in support of this idea by showing that two modified P elements, each with lesions affecting the fourth transposase exo...

A two-generation crossing program was used to replace the entire chromosome complement of P strains by M strain chromosomes, the maternal contribution being from the P strain. The cytotype of chromosomally substituted females was indistinguishable from M strain cytotype, judged by the sterility of offspring from the cross of such females to P strain males. In addition, following replacement of ...

Bryconamericus comprises 56 species distributed into three groups, on the basis of the position and shape of the maxillary teeth: B. exodon, B. microcephalus and B. iheringii groups. Few cytogenetic data are available for this genus, but the diploid number of 52 chromosomes is quite common, although the karyotypic variability is extensive. This study aimed to characterize a population of B. aff...

P elements inserted at the left telomere of the X chromosome evoke the P cytotype, a maternally inherited condition that regulates the P-element family in the Drosophila germline. This regulation is completely disrupted in stocks heterozygous for mutations in aubergine, a gene whose protein product is involved in RNA interference. However, cytotype is not disrupted in stocks heterozygous for mu...

Four populations of Astyanax hastatus Myers 1928 from the Guapimirim River basin (Rio de Janeiro State) were analyzed and three distinct cytotypes identified. These cytotypes presented 2n = 50 chromosomes, with 4M+8SM+10ST+28A (Cytotype A), 8M+10SM+14ST+18A (Cytotype B), 6M+8SM+4ST+32A (Cytotype C) and scanty heterochromatin, mainly located throughout pericentromeric regions of several chromoso...

Drosophila P-element transposition is regulated by a maternally inherited state known as P cytotype. An important aspect of P cytotype is transcriptional repression of the P-element promoter. P cytotype can also repress non-P-element promoters within P-element ends, suggesting that P cytotype repression might involve chromatin-based transcriptional silencing. To learn more about the role of chr...

To understand plant evolution and diversification, information regarding chromosome number meiotic behavior is imperative. The present study was carried out to determine the count, behavior, pollen fertility, seed set of a medicinally important Peganum harmala. Two cytotypes, diploid tetraploid are growing in western Himalaya; cytotype (2n=2x=24) Kashmir Himalaya, (2n=4x=48) Trans Ladakh. Chrom...

The future dispersal of onchocerciasis in Ecuador is dependent on the distribution of cytotypes of the vector species complex Simulium exiguum. Over the last 14 years, collections of larvae have been made from over 25 rivers, between 80-1600 m altitude, from various sites on both sides of the Andes. Analysis of larval polytene chromosomes was used to determine the distributions of each cytotype...