Some terminologies:

• Prepotency: Ability of animals to faithfully transmit the character to progeny.
• Nickling: Production of progeny that are superior to the parents that produce.
• Pleiotropy: Some has simultaneous effect on more than one trait.
• Dizygotic twins: Sets of twins derived from two separate fertilized egg.
• Repeatability: expression of same trait at different time in life of an individual.
• Top crossing: Mating of inbred males to females of non-inbred population.
• Grading up: Back crossing to the same breed takes place generation after generation.