What characterizes blond and red hair regarding melanin composition?

The characterization of blond and red hair in terms of melanin composition is indeed associated with a variant of melanin that includes iron or sulfur. Red hair specifically contains a type of melanin known as pheomelanin, which is lighter and has a yellow to reddish color due to its chemical composition that includes sulfur. Blond hair also has a high concentration of pheomelanin, although it may contain less overall melanin compared to darker hair colors.

This distinction in melanin types is crucial for understanding the way hair color is determined genetically, as eumelanin, the type of melanin responsible for darker hair shades (such as brown and black), is not the primary component in blond and red hair. Instead, the presence of pheomelanin, influenced by specific genes, leads to these lighter shades. Thus, the correct answer accurately captures the unique chemical makeup of the melanin in blond and red hair.