Principles of Genetics and Breeding

4.1.7.1 XX♀:XY♂ – system.

• Most common system found even in Man. XX female (homogametic), XY male (heterogametic).
• This type of system is reported in channel catfish, common carp, rainbow trout, sockeye salmon (Oncorhynchus nerka), coho salmon (O. kisutch), goldfish, nile tilapia, grass carp, murrels, Oryzias latipes, Poecilia reticulata, etc.
• The fact that XXY triploid rainbow trout are males suggests that a “dominant Y” sex-determining mechanism is operative.