Biochemistry – MCQ 60 – Complementary sequence of DNA

Which one of the following is the complementary sequence of 5′ TTAAGCGTAC 3′?
A. 5’ GTACGCTTAA 3′
B. 5’ AATTCGCATG 3‘
C. 5‘ CATGCGAATT 3’
D. 5’ TTAAGCGTAC 3’

Correct answer : A. 5’ GTACGCTTAA 3′

How to calculate the complementary sequence of DNA:

• Adenine binds with Thymine
• Guanine binds with Cytosine
• In the sequence given, make the following changes
  • Replace A with T
  • Replace T with A
  • Replace C with G
  • Replace G with C
  • Replace 5′ with 3′
  • Replace 3′ with 5′
• That gives you the complementary sequence of DNA!

Note: Using the above method, we get the complementary DNA sequence as 3′ AATTCGCATG 5′. This is the same as 5′ GTACGCTTAA 3′ – which corresponds to option A.