Question

First, ask the user to input a DNA sequence and store it in a variable called DNA_seq. Though in actual practice you should check if an input contains only DNA nucleotides, you do not have to do this for this lab. Then complete the following:

c)      Loop through the stored user input using “for j in range(len(DNA_seq))”. Within this loop, print out 3 statements: i) the current index number of the loop, ii) the character of DNA_seq at the current index number, and iii) the character of DNA_seq at the (current index number – 1).

[SIDE NOTE for part (c): Since this loop starts at j=0, you are allowed to print out the character at negative index values such as DNA_seq[-1]. Observe what is printed in each print statement. Your loop should print 3 statements per iteration.]

Answer 1

Code is in CPP. So DNA_seq[-1] indicates the last element so we print DNA_seq[DNA_length - 1] instead of DNA_seq[-1].

In Python DNA_seq[-1] will directly work but not in C or CPP .

CPP CODE:

#include <bits/stdc++.h>
using namespace std;

int main() {
   string DNA_seq;
   cout<<"Enter the DNA Sequence :";
   cin>>DNA_seq; // Taking the DNA_seq input from the user
   int length;
   length = DNA_seq.length(); //Calculating the length of DNA_seq
   int j = 0;
   for(j;j<length;j++){
       cout<<j<<" "<<DNA_seq[j]<<" "<<DNA_seq[(length + j - 1)%length]<<endl;

//Printing the seq_no present and previous character
   }
   return 0;

}
}