Final answer:
No, not all genes show simple patterns of dominant and recessive alleles. Some examples include incomplete dominance, codominance, and multiple alleles.
Step-by-step explanation:
No, not all genes show simple patterns of dominant and recessive alleles. While Gregor Mendel's experiments with pea plants suggested that traits follow a simple dominant and recessive pattern, there are several important modes of inheritance that do not follow this model. Some examples include incomplete dominance, codominance, and multiple alleles. Incomplete dominance is when neither allele is completely dominant over the other, resulting in a blended phenotype. Codominance is when both alleles are expressed simultaneously, resulting in a phenotype that shows features of both alleles. Multiple alleles occur when more than two alleles exist for a given gene at the population level.