Abnormalities in shellfish are common. In one type of abnormality, the DNA of the shellfish contains an extra nitrogen base pair. This would be a result of

Gene mutation

Explanation: Gene mutation is a biological term used to describe the change in the genetic sequence or nucleotide composition of one or more of the gene composition of an organism, this gene mutation usually leads to abnormalities in the affected organism as described in the above question, the DNA of the shellfish contained an extra Nitrogen base pair which has made it different from other shelf fishes.

answer; /// i believe that the correct answer is ( monophasic ); ethinyl estradiol- ethynodiol diacetate is a monophasic oral contraceptive agent; ///