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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 .
 GENE: activated human Ha - ras; GENE: bacterial lactose operon regulatory elements; GENE: dihydrofolate reductase; GENE: dhfr; GENE: mutant Ha - ras
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 GENE: activated human Ha - ras; GENE: bacterial lactose operon regulatory elements; GENE: dihydrofolate reductase; GENE: dhfr; GENE: mutant Ha - ras