Complex sentence: The genetic abnormality occurs randomly in sperm or egg cells or it may occur in early embryonic growth, if it occurs during embryonic growth the ring chromosome may be present in only some of a person's cells.
Split into simpler sentences: The genetic abnormality occurs randomly in sperm or egg cells or it may occur in early embryonic growth. If it occurs during embryonic growth the ring chromosome may be present in only some of a person's cells.