Question

In python!

Objective:

students will be able to

1.access string elements by index operator

2.search for simple pattern in strings

Specification:

Biologists use a sequence of letters A, C, T, and G to model a genome. A gene is a substring of a genome that starts after a triplet ATG and ends before a trilet TAG, TAA, or TGA. The length of a gene string is a multiple of 3 and the gene does not contain any of the triplets ATG, TAG, TAA, and TGA. Write a program that prompts the user to enter a genome and displays all genes in the genome. If no gene is found in the input sequence, the program displays "No gene is found". Here are the sample runs:

Enter a genome string: TTATGTTTTAAGGATGGGGCGTTAGTT [ENTER]

TTT

GGGCGT

Enter a genome string: TGTGTGTATAT [ENTER]

No gene is found

Answer 1

Program:

Sample output:

RUN1:

RUN2:

Code to copy:

#define main method
def main():

    #prompt the user to enter genome string
    print("Enter a genome string: ")
    string=input();

    #declare all the required variables
    i=0
    found=0
    start=-1

    #find the length of the string
    num=len(string)
    for i in range(num-2):

        #find the substring of genome string
        triplet=string[i:i+3]

        #compare the substring with following strings
        if triplet=="ATG":
            start=i+3
        elif triplet=="TAG" or triplet=="TAA" or triplet=="TGA" and start!=-1:
            gene=string[start:i]
            if len(gene)%3==0:
                found=1

                #print the substring
                print(gene)
                start=-1
    #check if there is no gene string
    if found==0:
        print("no gene is found")         
main()