Which of the following is true regarding traits expressed in a heterozygous individual?

In a heterozygous individual, where one allele is dominant and the other is recessive, it is the dominant trait that is expressed. This phenomenon is a foundational principle of Mendelian genetics. The dominant allele masks the effect of the recessive allele, meaning that the observable characteristics (phenotype) will reflect the dominant trait instead of the recessive one.

For example, in a scenario where an individual carries one allele for brown eyes (dominant) and another for blue eyes (recessive), the individual will display brown eyes due to the dominance of the brown allele.

The other options do not accurately describe the situation. Traits expressed equally would suggest co-dominance or incomplete dominance, which applies to certain genetic conditions but not to classic Mendelian inheritance. The expression of the recessive trait would only occur if an individual were homozygous recessive, having two copies of the recessive allele. Lastly, the statement that none of the traits would be expressed would contradict the basic understanding of how dominant and recessive traits function in genetics.