A student claims that dominant traits are always the most common traits. Is this true why or why not?
No, this claim is not true. Dominant traits are not always the most common traits in a population.
Dominant traits refer to traits that are more likely to be expressed in an individual's phenotype when at least one copy of the dominant allele is present. On the other hand, recessive traits require two copies of the recessive allele for them to be expressed.
The frequency of a trait in a population depends on various factors such as the mode of inheritance, selection pressures, mutation rates, migration, genetic drift, and other evolutionary processes. Sometimes, dominant traits may be more common in a population, but this is not always the case.
In fact, recessive traits can remain hidden or "carried" in a population for generations without being expressed. For instance, if a recessive allele is rare, it may be present in a population's gene pool but not frequently observed phenotypically. In such cases, the recessive trait would not be the most common, even if it is present in the majority of individuals at the genetic level.
Therefore, the commonness or rarity of a trait in a population is not solely determined by whether it is dominant or recessive, but rather a combination of various genetic and environmental factors.