Complex sentence: Genes can be the common factor of the qualities of most human-inherited traican be useful as it can answer questions about human nature, understand the diseases and development of effective disease treatment, and understand genetics of human life.
Split into simpler sentences: Genes can be the common factor of the qualities of most human-inherited traits. Study of human genetics can be useful as it can answer questions about human nature, understand the diseases and development of effective disease treatment, and understand genetics of human life.