Final answer:
Genetic traits are expressed through proteins produced by genes, which determine an organism's observable phenotype. The central dogma of molecular biology describes this process, and gene expression is regulated based on the cell's requirement for specific proteins.
Step-by-step explanation:
Genetic traits are indeed expressed through the actions of proteins. The observable traits expressed by an organism are described as its phenotype, which is a product of the proteins produced by the cell's genes. The central dogma of molecular biology states that DNA encodes messenger RNA, which, in turn, encodes protein.
An organism's traits are determined by the specific combination of inherited genes, and these genes are responsible for producing proteins. It's also important to note that although an organism's genotype remains constant, genes are only expressed when their associated proteins are needed.