Final answer:
Gene expression and its influence on phenotypes are complex, with factors such as polygenic inheritance and environmental effects.
Step-by-step explanation:
Understanding Gene Expression and Phenotypes
Not all inherited genes directly influence the phenotypes of offspring. Phenotypes, the observable traits expressed by an organism, are a result of the combined effects of genes and their interaction with the environment. An example of this is polygenic inheritance, where traits like human skin color or height are influenced by multiple genes. In these cases, genes can express sequentially or in a complementary or synergistic manner to contribute to a common phenotype.
Moreover, the field of epigenetics studies how environmental factors can influence gene expression. Identical twins, for example, may have the exact same genotype, yet exhibit different phenotypes due to environmental influences on their gene expression throughout their lives. This shows that while the genetic composition remains the same, the expression of genes is dependent on external conditions and can greatly influence the phenotype.
Interactions such as epistasis further complicate expression, where one gene can mask or modify the expression of another, resulting in a phenotype that does not follow classical Mendelian genetics. These complex inheritance patterns show that the relationship between genotype and phenotype is intricate and influenced by multiple factors.