Final answer:
True. Alleles can indeed exhibit various degrees of dominance and recessiveness, which is a more complex reality than Mendel's original model suggested. Phenomena like incomplete dominance and codominance, as well as the existence of multiple alleles in a population, contribute to this complexity.
Step-by-step explanation:
The statement that alleles can show different degrees of dominance and recessiveness in relation to each other is True. While Mendel's law of dominance suggests that a dominant allele will mask the presence of a recessive allele in a heterozygote, this is an oversimplification. In reality, the pattern of inheritance can be more complex. For example, incomplete dominance occurs when the heterozygote exhibits a phenotype that is intermediate between the phenotypes of both homozygotes.
With codominance, both alleles in the heterozygote are fully expressed, as seen in human blood types. Moreover, there may be multiple alleles at the population level, resulting in various potential combinations. While the most common phenotype in a natural population is often denoted as the wild type, other variants may be dominant or recessive to this wild-type allele.