1. Methods: Both karyotypic analysis and Y chromosome were performed in 107 blood specimen from azoospermic men.

2. Genetic Chimerism, the mingling of two or more genomic lineages within an individual (), is rare in mammals, but Chimerism is prevalent in the hematopoietic tissues of marmosets and other callitrichid primates (2, 3).In these species, fraternal twins exchange cell lines through chorionic fusion during early development (2, 4, 5).On the basis of karyotypic evidence from Callithrix jacchus (2, 3

3. Two species evidenced special hybridization sites with the telomeric probe: (i) interstitial heterochromatic blocks in particular long chromosomes in S. salar, this observation supports tandem fusions as the karyotypic evolutionary mechanism leading to the formation of the long acrocentric and submetacentric chromosomes in the karyotype of S. salar; (ii) the whole NOR region in O. mykiss; this observation suggests that the (TTAGGG)n sequence is scattered all along this chromosome region.