Estimating coancestry within open-pollinated progenies of a dioecious species: the case study of Myracrodruon urundeuva

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Genetic Variation in an International Provenance-Progeny Test of Pinus caribaea Mor. var. bahamensis Bar. et Gol., in São Paulo, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Observations which indicate heterochromatinization of an extra chromosome in the salivary gland cells of Drosophila hybrids

Salivary gland cells of Drosophila mulleri/D. arizonensis aneuploid male hybrids carrying 3 microchromosomes exhibited morphological features which indicate heterochromatinization of one of the small polytene chromosomes. The process apparently changes the chromosome surface producing a coating with a net-like structure and a strong affinity for lacto-acetic orcein. The possibility of a dosage compensatory mechanism operating to counteract the effect of the extra chromosome is discussed on the basis of previous data which indicated that the microchromosomes of these species have ribosomal cistrons and are controlled by regulatory mechanisms especially evident in hybrids. © 1981 Dr W. Junk Publishers.

Constitutive heterochromatin, G-bands and nucleolus-organizer regions in four species of Didelphidae (Marsupialia)

Chromosomes of Didelphis albiventris, D. marsupialis, Philander opossum and Lutreolina crassicaudata, four species of marsupials with very similar karyotypes and 2n=22 were studied. All the chromosomes were acrocentrics except the X in L. crassicaudata, which is a metacentric. The G-band patterns of these species are similar but the distribution of constitutive heterochromatin differs among them as shown by C-banding. The hypothesis that the X in L. crassicaudata might be an isochromosome derived from the acrocentric X in the other species is discarded since G-and C-banding patterns differ in the two arms. In D. marsupialis the Ag-NORs are terminal and located in both arms of one pair and in the long arms of two pairs of medium-sized autosomes. In P. opossum the NOR-bearing chromosomes could be precisely identified through simultaneous silver staining and G-banding. The Ag-NORs are terminal and located at the short arm of pair 5 and the long arm of pair 7. © 1982 Dr W. Junk Publishers.

Spontaneous triploidy and NOR activity in Eigenmannia sp. (Pisces, Sternopygidae) from the Amazon basin

The occurrence of a natural triploid among diploid individuals of Eigenmannia sp from the Amazon basin is described. The diploid individuals had 2n=31 and 32 chromosomes, the difference in chromosome number being due to a Robertsonian rearrangement. The triploid individual presented 2n=46 and had two fused acrocentrics. NOR activity was present in the three homologues of triploid and a NOR polymorphism was detected in the triploid and diploids. © 1985 Dr W. Junk Publishers.

Characteristics of NOR-banded chromosomes of Mangalarga horses

The nucleolar organizer regions (NORs) of Mangalarga horses were characterized by analysis of NOR-banded metaphase chromosomes according to the technique of Goodpasture and Bloom (Chromosoma 53: 37-50, 1975). NOR banding was detected by silver staining in the telomeric region of the short arm of pair no. 1, in the region adjacent to the centromere of the long arm of pair no. 25 and in the proximal region of the long arm of pair no. 31. Associations of NOR-bearing chromosomal regions occurred in 12% of all metaphases and were frequent between the chromosomes of pair no. 1. Most (52.15%) of the NOR bands appeared on four chromosomes in both males and females. The maximum number of NOR-banded chromosomes was six, though only 11.34% of the cells examined showed this characteristic.

A case of terminal long arm deletion of chromosome 6

A four-year-old girl with deletion of chromosomal band 6q24 → qter is described. Clinical features include growth and psychomotor retardation, microcephaly, convergent strabismus, bulbous nose, long philtrum, short neck and cardiopathy.