In Mendelian genetics, what is true about dominant alleles?

Dominant alleles are characterized by their ability to mask the expression of recessive alleles when both are present in an individual. When an organism inherits one dominant allele and one recessive allele for a trait, the phenotype associated with the dominant allele will be expressed. This ability to be expressed alongside a recessive allele explains why dominant traits can often be seen in the phenotype even when the organism carries a recessive allele as well.

The idea of dominance in alleles means that when a dominant allele is present, it typically takes precedence in determining the trait exhibited. For example, in a trait governed by two alleles—one dominant (A) and one recessive (a)—an individual with genotypes AA or Aa will display the trait associated with the dominant allele A, while only the genotype aa will express the recessive trait.

This understanding of how alleles interact is foundational in Mendelian genetics, as it informs us about inheritance patterns and the expression of traits across generations. Dominant alleles play a crucial role in genetic variability and phenotypic expression, shaping how traits are passed down through families.