What are traits controlled by?

Most human traits have complex modes of inheritance. They may be controlled by onegene with multiple alleles or by multiple genes. More complexity may be introduced by pleiotropy (one gene, multiple effect) and epistasis (gene-gene interactions). Many genetic disorders are caused by mutations in one or a few genes.

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.