The drastic reduction in diploid number from 48 chromosomes to 2n = 36 and 2n = 34, respectively, along the presence of large metacentric
pairs is evidence of sequential Robertsonian rearrangements or centric fusions (Figures 2(c) and 2(e)).
Telomeric C-bands were observed mostly in the telomeres of a metacentric
chromosome and a submetacentric chromosome.
The neo-X is thus metacentric
, with one of its arms corresponding to the ancestral X positive heteropycnotic during the first prophase, while the other arm, formed by the A1 chromosome, is isopicnotic.
cariba displayed a karyotype 2n= 60, comprised of 9 pairs of metacentric
(M), 15 pairs of submetacentric (SM), 1 pair of subtelocentric (ST) and 5 pairs of acrocentric chromosomes.
The FM2 race retains the metacentric
morphology only in the form of a Robertsonian polymorphism at chromosome 4.
1a) (2n = 92), with 8 pairs of metacentric
(M) and 38 pairs of acrocentric chromosomes (a), and with karyotype formula 2K = 16M +76A (Fig.
The chromosomes were classified as metacentrics
(m), submetacentrics (sm), subtelocentrics (st) and acrocentrics (a) according to their morphology and arm ratios (Levan et al., 1964; Guerra, 1988).
antenori presented 2n = 48 chromosomes, with a karyotype composed of 6 metacentrics
, 4 submetacentrics, and 36 subtelocentrics (NF = 96, number of chromosome arms).
The mean arm ratios indicated that this species has 16 pairs of clearly metacentric
chromosomes (chromosome pairs 1-16; Table 2).
The neo-sex system resulted from an X/L3 fusion which has converted the acrocentric X element into a metacentric
neo-X, while the unfused L3 autosome behaves as a neo-Y element.
Occurrence of a metacentric
macrochromosome B in different species of the genus Astyanax (Pisces, Characidae, Tetragonopterinae).
Bole-Gowda (1952) stated that Heteropoda sexpunctata Simon 1885 has a derived karyotype, 2n = 20 + X (male) with 19 metacentric
(including the X chromosome) and two acrocentric autosomes, on the basis of Robertsons law.