Question

Genes that are involved in turning on or off the transcription of a set of structural genes are called as

• A. Polymorphic genes
• B. Operator genes
• C. Redundant genes
• D. Regulatory genes

Answer 1

The correct option is D Regulatory genes

Regulator gene regulates the expression of structural genes by its protein products that are mostly transcription factors. These transcription factors bind to the operator region which is located just upstream the binding site of the RNA polymerase and hence prevent the binding and transcription; option D is correct. Operator is a DNA sequence present between the promoter region and the first coding gene. This operator region serves as repressor protein binding site; option B is wrong. Genes which govern more or less same trait or perform same role are called redundant genes; presence of these genes confers advantage of diluting the effect of point mutation on organisms; option C is wrong. Presence of more than one allele on a genetic locus is called gene polymorphism provided that the allele is present with more than 5% frequency in the population; option A is wrong.