If tallness appears in the first generation when a tall pea plant is crossed with a dwarf pea plant, what type of trait is tallness?

Correct answer: Dominant trait

The governing concept is Mendel’s principle of dominance. When contrasting pure traits are crossed, the trait expressed in the first filial generation masks the alternative trait. In the classic pea-plant example, allele T for tallness is dominant over allele t for dwarfness; the hybrid has genotype Tt and is tall. Therefore, tallness is the dominant trait, not an acquired, harmful, or recessive trait.