Question

What will be the complementary strand sequence of DNA produced during DNA replication of the following given sequence of DNA?
3' - CAGACCTGGA - 5'

• A. 5' - ATGCTGAACT - 3'
• B. 5' - GTCTGGACCT - 3'
• C. 5' - GACCTGATGC - 3'
• D. 5' - GCATCAGGTC - 3'
• E. 5' - TACGACTTGA - 3'

Answer 1

Answer: (B)

5' - GTCTGGACCT - 3'

As we know that two strands of DNA are antiparallel to each other and have opposite polarity. This means that 5’ phosphate of one strand faces 3’ hydroxyl group of other strand and that the 5’ phosphate groups of two strands are present in opposite position. Antiparallel arrangement of two helices allows hydrogen bonding between amino and carbonyl group of complementary base pairs (A pairs with T and G with C). Hence, the complementary strand of 3’ CAGACCTGGA 5’ will be 5’ GTCTGGACCT 3’. Therefore, the correct answer is option B.