Chromosome banding in Amphibia

Abstract

The mitotic chromosomes of an Ecuadorian population of the marsupial frog Gastrotheca espeletia were analyzed by means of banding techniques and fluorescence in situ hybridization. This species is characterized by unusual supernumerary (B) chromosomes. The maximum number of B chromosomes is 9 and they occur in three different morphological types. Banding analyses show that the B chromosomes are completely heterochromatic, consist of AT base pair-rich repeated DNA sequences, replicate their DNA in very late S-phase of the cell cycle, and are probably derived from a centromeric or paracentromeric region of a standard (A) chromosome. Exceptionally, the B chromosomes carry 18S + 28S ribosomal RNA genes and the conserved vertebrate telomeric DNA sequence appears to be underrepresented. Flow cytometric measurements of the nuclear DNA content differentiate between individuals with different numbers of B chromosomes. Significantly more B chromosomes are present in female than in male animals.

Cytogenetic analysis of two species in the Phyllomedusa hypochondrialis group (Anura, Hylidae)

“…Both P. rohdei and P. nordestina displayed only one pair of NORs per diploid genome, which, according to SCHMID (1978) andSCHMID et al (1990), is a common characteristic of anurans. Usually, the NORs are located on the same chromosome pair in species belonging to the same group or even in related species.…”

“…Pair 9 of the P. rohdei specimens from Ilh é us/BA analyzed in this study seems to be similar to pair 11 from specimen MZESC 5610 analyzed by BARTH et al (2009) because they have similar size, the same submetacentric morphology and same NOR position. The genomic position of the NOR is a very informative marker for the taxonomy and phylogeny of anurans ( SCHMID 1978;ODIERNA et al 2000;ANDREONE et al 2003), and interspecies NOR variations indicate possible chromosomal rearrangements (translocations and/or inversions) of chromatin segments containing rDNA during the chromosomal evolution process ( SCHMID et al . 1990).…”

Nucleolus organizer polymorphism in barley, Hordeum vulgare L.

“…Further, they were of differing ages (as selected lines) and geographical regions ( Table 1). The C-banding patterns of most lines had previously been studied (LINDE-LAURSEN 1978, 1982: LINDE-LAURSEN et al 1982). The lines 'Orel '.…”

“…Each metaphase had 14 well-spread, not overcontracted chromosomes, of which at least two showed secondary constrictions. In all other lines at least five cells were studied in unstained preparations by means of phase-contrast optics in combination with Cbanding (LINDE-LAURSEN 1978, 1982: LINDE-LAUR-SEN et al 1982. The number and relative size of silver nitrate-stained NORs were counted and subjectively estimated, respectively, in 50 cells of each of the lines 'Doris', 'Orel' (CI 351), 'Wong', and 'T6-7k' and in at least five cells of each of the other lines.…”

“…Previously, the karyotype of barley was considered uniform, but the introduction of Giemsa C-and N-banding techniques has revealed an unrecognized variation in the chromosomes (LINDE-LAURSEN 1978, 1982LINDE-LAURSEN et al 1982). Giemsa does not stain the chromosomal material of the secondary constrictions.…”