If the sequence of one strand of DNA is written as: 5'- ATCGTGCTATGAGCATGC-3'.

The sequence of its complementary strands will be?

3'- TAGCACGATACTCGTACG-5'

The correct answer is Option (2) → 3'- TAGCACGATACTCGTACG-5'

Explanation:

The given DNA strand is:
5'- ATCGTGCTATGAGCATGC -3'

To find the complementary strand:

1. Base Pairing Rules:
• A (Adenine) pairs with T (Thymine)
• T (Thymine) pairs with A (Adenine)
• C (Cytosine) pairs with G (Guanine)
• G (Guanine) pairs with C (Cytosine)
2. Complementary Sequence:
• Write the complementary bases in the opposite direction (3' → 5') to maintain antiparallel structure.

Given Strand (5'→3'):
TCGTGCTATGAGCATGC

Complementary Strand (3'→5'):
TAGCACGATACTCGTACG

Other Options:

• Option 1: Incorrect because it is written 5'→3' (should be 3'→5').
• Option 3 & 4: Incorrect because they contain Uracil (U), which is found in RNA, not DNA.