Inverted and satellited Y chromosome in the orangutan (Pongo pygmaeus)

An inverted and satellited Y chromosome of almost acrocentric appearance was detected in seven of 14 male orangutans. In the remaining seven animals a submetacentric Y chromosome without NORs occurred. The high frequency with which the satellited Y chromosomes were associated with acrocentric autosomes and the positive AgNO3-staining of their satellite stalks clearly indicate the active state of the NOR on the Y chromosomes. DNA fingerprinting in two orangutan families showed that the inverted and satellited Y chromosomes in carrier orangutan males do not interfere with normal fertility. Within our sample of male orangutans studied, the inverted and satellited Y chromosome is restricted to Sumatran animals; all Bornean specimens possessed the submetacentric Y chromosome. The question arises whether these two kinds of Y chromosome differ constitutively between the Pongo pygmaeus subpopulations.