You will be given a definition of a task first, then some input of the task.
In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.

To better understand the relationship between expression of an oncogene and genetic instability , we have studied a cell line expressing an activated human Ha - ras under the control of bacterial lactose operon regulatory elements for changes in methotrexate resistance and dihydrofolate reductase ( dhfr ) gene amplification following mutant Ha - ras induction .
Output:
dihydrofolate reductase