"the isolation of cell-cycle mutations in yeast was greatly facilitated by the use of mutations, which allow investigators to study the effects of mutations that would be lethal if expressed constantly"

The correct answer is - conditional mutation.

Explanation:

Conditional mutation is a type of mutation that has less severe or wild-type phenotype or traits that physically appears under particular permissive environmental conditions and a mutant phenotype under particular restrictive environmental conditions.

Thus, the correct answer is a conditional mutation.

economic impact of malaria is estimated to cost africa $12 billion every year. this figure factors in costs of health care, absenteeism, days lost in education, decreased productivity due to brain damage from cerebral malaria, and loss of investment and tourism.