21. Which genotype would be used to indicate an individual that has no recessive alleles?
Answer: D
AABB indicates an individual that has no recessive alleles.
The genotype AABB represents an individual who possesses only dominant alleles for both traits, indicating the absence of any recessive alleles.
A) AAbb
The genotype AAbb contains one recessive allele (bb), which means this individual has at least one trait influenced by a recessive allele. Therefore, this option is incorrect as it does not fulfill the criteria of having no recessive alleles.
B) aaBB
The genotype aaBB also has recessive alleles present (aa), which indicates that this individual expresses a recessive trait. Thus, this option is incorrect as it does not represent an individual without any recessive alleles.
C) aabb
This genotype consists entirely of recessive alleles (aa and bb), meaning it is characterized by expressing recessive traits for both genes. Consequently, this option is incorrect since it clearly contains recessive alleles.
D) AABB
The genotype AABB is composed entirely of dominant alleles, indicating that the individual does not have any recessive alleles. This option correctly meets the requirement outlined in the question.
Conclusion
The genotype AABB is definitively correct as it signifies an individual with no recessive alleles present. In contrast, the other options each contain at least one recessive allele, disqualifying them from being considered as individuals without recessive traits.