Brothers, Patrick and Michael, do not look very much alike. Patrick has green eyes and blond, curly hair like his mother. Michael has blue eyes and dark brown, straight hair like his father. These directly observable characteristics are a) phenotypes. b) genotypes. c) chromosomes. d) DNA.

The correct answer is A. Phenotypes

Explanation:

In genetics, the observable traits of an organism that includes behavior, physical traits, biochemical properties, etc. are known as phenotypes. These traits depend on both the genes of the organism (genotype) and the influence of the environment. Due to this, organisms of the same species with a similar genotype can display different phenotypes. This occurs in the case of Patrick and Michael as their observable traits or phenotype is different despite they are brothers. Thus, the observable characteristics are the phenotypes of an organism.