Final answer:
Abnormal genes causing recessive diseases can be transmitted through many family generations before causing the expression of the disease.
Step-by-step explanation:
True. Abnormal genes causing recessive diseases can be transmitted through many family generations before causing the expression of the disease. This is because recessive diseases require an individual to inherit two copies of the abnormal gene, one from each parent, in order to show symptoms of the disease. If only one copy of the abnormal gene is inherited, the individual is considered a carrier and does not show symptoms of the disease.