Recessive alleles are best defined as recessive alleles are best defined as a deleterious or disease-causing allele a weakened or attenuated allele an allele only expressed when the allele is homozygous the least frequently expressed allele in a given population

a deleterious or disease-causing allele  (may not always be the case, it may simply be expressing other phenotypic trait which is not harmful to the organism)

a weakened or attenuated allele (may not be the case, recessive alleles are not indicative of the strength of the allele)

an allele only expressed when the allele is homozygous (correct answer)

the least frequently expressed allele in a given population (not true, recessive alleles do not necessairily mean it is the least frequently expressed allele)

check for the pregnancy rating of drug. if its class c or d see if other alternatives