Answer:
When a trait is shown and at least one letter is upper case, it is a dominant allele (option A).
Explanation:
In genetics the presence of a dominant allele - represented by a capital letter - is sufficient to suppress a recessive allele, expressing the dominant trait in the phenotype.
Dominance is based on allelic combinations of the genotype, which are expressed in the phenotype for a given characteristic:
- Two dominant alleles (AA) express the only possible trait, dominant.
- One dominant allele and one recessive allele (Aa) show a dominant phenotype, as the former suppresses the latter. It is a hybrid or heterozygous.
- Two recessive alleles (aa) show a phenotype with the recessive trait.
The other options are not correct, because:
B) Recessive is the allele that is only expressed in the phenotype when there is a pair in the gene.
C) Trait is equivalent to a characteristic.
D) Allele represents the different ways in which a gene is expressed.
