Introduction

Your company is involved with making genetic modifications to viruses to reduce their harm to humans.They accomplish this by removing some elements from a virus’s DNA sequence.The DNA is composed of a sequence of chemicals represented by a 2 letter codes such as “RA” or “DD”.Here is an example of the first 6 elements of a DNA sequence:RAJARDDARRJA … (the sequence could be thousands or millions of elements long).
Your boss has asked you to write an interactive program that will allow users to remove elements from a DNA sequence.The program should be responsive (after a user enters a command, the program should complete the user’s request within one second even if the DNA sequence is long).

Instructions
Write a program that reads a DNA sequence from a text file and then allows a user to choose what type of elements to remove from the sequence.All elements containing the letter or letters entered will be removed from the sequence.For example, if the user chose to remove “JA” from the example sequence above, the DNA sequence would become RARDDARR ….Then if the user chooses to remove “D”,the DNA sequence would become RARR ….(both elements containing D would be removed).After the user is done making modifications the program should output the modified DNA sequence to a file called ‘output.txt’ (see sample program run below).

You will be provided with 3 text files containing DNA sequences.The first file is called “testSequence.txt”.This contains the sequence in the example described above.The second file is called “shorterSequence.txt”.It contains a DNA sequence that is 200,000 elements long.Running the program and removing all elements containing R will shorten the DNA sequence to 112,528 elements.The third file is called “longerSequence.txt”.It contains a DNA sequence with 2 million elements.