Final answer:
Less frequent alleles with genetic changes that result in defective protein production are called recessive alleles. Mutations in DNA lead to proteins that may not function correctly and these alleles are termed recessive because one normal allele can compensate for the defective one.
Step-by-step explanation:
Less frequent alleles that have genetic changes making them defective in protein production are called recessive alleles. Genetic mutations in DNA can lead to the production of defective proteins or cease protein production entirely if not corrected.
These mutations can be spontaneous or caused by environmental factors. When such mutations occur at the level of tRNA and rRNA, they can lead to proteins that do not function correctly, such as in sickle cell anemia, which results from a missense mutation replacing glutamic acid with valine, dramatically affecting the hemoglobin protein's function. These alleles are termed recessive because a single normal allele can overshadow the defective one and produce enough functional protein to give a normal phenotype.