Karyological analysis and nature polymorphics of nucleolar organizer regions in the dusky leaf monkey, trachypithecus obscurus (primate, colobinae), by conventional, GTG-, CBG-banding, and high-resolution techniques

Abstract

A discovery of polymorphic nucleolar organizer regions (NORs) and karyological analysis in the dusky leaf monkey (Trachypithecus obscurus) from Thailand were studied. Blood samples were taken from 2 male and 1 female leaf monkeys. After standard whole blood lymphocytes had been cultured at 37°C for 96h in presence of colchicine, metaphase spreads were performed on microscopic slides and air-dried. Conventional, GBG-, CBG-banding and high-resolution techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of T. obscurus was 2n=44 and the fundamental number (NF) for both sexes was 88. The types of autosomes were 6 large metacentric, 12 large submetacentric, 2 large acrocentric, 4 medium metacentric, 10 medium submetacentric, 2 small metacentric, 4 small submetacentric, and 2 small acrocentric chromosomes. The X chromosome was a large submetacentric chromosome and the Y chromosome was a small submetacentric chromosome. In addition, the long arm near centromere of chromosome pair 17 showed clearly observable NORs. This is the first report on nature polymorphism in NORs in T. obscurus. The results showed that a heteromorphism of 1 female had different size of NORs forchromosome pair 17s, while 2 males had an equal size of both chromosome pair 17s with a homomorphism. From the GTG-banding and high-resolution techniques, the numbers of bands and locations in the T. obscurus were 235 and 314, respectively, and each chromosome pair could be clearly differentiated. CBG-banding showed C-positive (dark bands) on the centromeres of all autosomes but showed C-negative (light bands) on the Y chromosome. Moreover, we also found interstitial dark bands on the telomeres of long arms which result from centric fusion or tandem fusion. The karyotype formula for T. obscurus could be deduced as: 2n (diploid) 44=L 6mL 12sm+L 2a+M 4m+M 10sm+S 2m+ S 4sm+S 2a+ sex chromosomes. © 2012 The Japan Mendel Society.