Method 1: Verify if a sequence is DNA and RNA

Step 1:

In the set method, we convert the input sequence into a set. We combine the set obtained with a reference DNA set(ATGC) or RNA set(AUGC) using the union function of the set. This is done so that the input sequence is rendered valid even if it does not contain all four types of nucleotide bases. For instance, TTTTTTTAAA is a valid DNA even though it contains only two types of bases. Also, UUUUUUUUGGG is a valid RNA.

Python3

def verify(sequence):
    '''This code verifies if a sequence is a DNA or RNA'''
    # set the input sequence
    seq = set(sequence)
     
    # confirm if its elements is equal to the
    # set of valid DNA bases
    # Use a union method to ensure the sequence is
    # verified if does not contain all the bases
    if seq == {"A", "T", "C", "G"}.union(seq):
        return "DNA"
    elif seq == {"A", "U", "C", "G"}.union(seq):
        return "RNA"
    else:
        return "Invalid sequence"
 
 
seq1 = "ATGCAGCTGTGTTACGCGAT"
seq2 = "UGGCGGAUAAGCGCA"
seq3 = "TYHGGHHHHH"
 
print(seq1 + " is " + verify(seq1))
print(seq2 + " is " + verify(seq2))
print(seq3 + " is " + verify(seq3))

Output:

ATGCAGCTGTGTTACGCGAT is DNA
UGGCGGAUAAGCGCA is RNA
TYHGGHHHHH is Invalid sequence

Step 2:

This function returns a reverse complement of a DNA or RNA strand.

Python3

def verify(sequence):
    '''This code verifies if a sequence is a DNA or RNA'''
     
    # set the input sequence
    seq = set(sequence)
     
    # confirm if its elements is equal to 
    # the set of valid DNA bases
    # Use a union method to ensure the
    # sequence is verified if does not
    # contain all the bases
    if seq == {"A", "T", "C", "G"}.union(seq):
        return "DNA"
    elif seq == {"A", "U", "C", "G"}.union(seq):
        return "RNA"
    else:
        return "Invalid sequence"
 
 
def rev_comp_st(seq):
    '''This function returns a reverse complement 
    of a DNA or RNA strand'''
    verified = verify(seq)
    if verified == "DNA":
       
        # complement strand
        seq = seq.replace("A", "t").replace(
            "C", "g").replace("T", "a").replace("G", "c")
        seq = seq.upper()
         
        # reverse strand
        seq = seq[::-1]
        return seq
 
    elif verified == "RNA":
       
        # complement strand
        seq = seq.replace("A", "u").replace(
            "C", "g").replace("U", "a").replace("G", "c")
        seq = seq.upper()
         
        # reverse strand
        seq = seq[::-1]
        return seq
    else:
        return "Invalid sequence"
 
 
# test variables
seq1 = "ATGCAGCTGTGTTACGCGAT"
seq2 = "UGGCGGAUAAGCGCA"
seq3 = "TYHGGHHHHH"
 
print("The reverse complementary strand of " +
      seq1 + " is " + rev_comp_st(seq1))
print("The reverse complementary strand of " +
      seq2 + " is " + rev_comp_st(seq2))
print("The reverse complementary strand of " +
      seq3 + " is " + rev_comp_st(seq3))

Output:

The reverse complementary strand of ATGCAGCTGTGTTACGCGAT is ATCGCGTAACACAGCTGCAT

The reverse complementary strand of UGGCGGAUAAGCGCA is UGCGCUUAUCCGCCA

The reverse complementary strand of TYHGGHHHHH is Invalid sequence

Reverse complement of DNA strand using Python

In this article, we will cover, how to Reverse the complement of DNA or RNA sequences in Python.

Example:

DNA strand: ATGCCGAGCA
Complementary Strand: TACGGCTCGT
Reverse-Complementary strand: ACGAGCCGTA

Method 1: Verify if a sequence is DNA and RNA

Python3

Python3

Reverse complement of DNA strand using Python

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