Mysterious organism part 7

Hi, I’m working on the mysterious organism project. I created a single instance of the object as a test, using the mockUpStrand() helper function to assign a value to a DNA strand. When I run the code more than once, I’ve noticed that I’m getting a totally new DNA sequence each time I run the code. How do I utilize mockUpStrand() to create a randomized DNA strand, then store a specific value that won’t change every time the code is run, or does it even matter?

// Returns a random DNA base
const returnRandBase = () => {
  const dnaBases = ['A', 'T', 'C', 'G'];
  return dnaBases[Math.floor(Math.random() * 4)];
};

// Returns a random single stand of DNA containing 15 bases
const mockUpStrand = () => {
  const newStrand = [];
  for (let i = 0; i < 15; i++) {
    newStrand.push(returnRandBase());
  }
  return newStrand;
};

const pAequorFactory = (num, bases) => {
  return{
    specimenNum: num,
    dna: bases,
    set mutate(dna){
      const rand = Math.floor(Math.random());
      return this.dna[rand].push(returnRandBase()!==this.dna[rand]);
    },
    compareDNA(obj){
      const sameDNA = [];
      for(let i=0; i<dna.length; i++){
        if(this.dna[i]===this.bases[i]){
          sameDNA.push(this.dna[i]);
        }
      }
      const percentage = (sameDNA.length/this.dna.length).toFixed(2)*100;
      return `${this.specimenNum} variant #1 and variant #2 have ${percentage}% of their DNA in common`;
    },
    willLikelySurvive(arr){
      const cG = arr.filter(i=>{arr[i]==='C'||arr[i]==='G';});
      ((cG.length/arr.length)*100)>=60? true:false;
    }
  }
}

// const pAequor1 = pAequorFactory(1,mockUpStrand());
// console.log(pAequor1)
const first = mockUpStrand();
console.log(first);