Final answer:
Two different traits may commonly be expressed together because of linkage or polygenic inheritance.
Step-by-step explanation:
Two different traits may commonly be expressed together because of linkage or polygenic inheritance.
Linkage occurs when genes for different traits are located close together on the same chromosome, causing them to be inherited together. For example, genes for hair color and eye color are often linked, resulting in certain hair and eye colors being inherited together.
Polygenic inheritance happens when multiple genes contribute to a common phenotype. Complex traits like human skin color or height are influenced by the combined effects of many genes.