If the sequence of one strand of DNA is written as follows: 5'-ATGCATGCATGCATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of complementary strand in 5'–3' direction.
To write the sequence of the complementary strand in the 5'–3' direction, we must apply the principle of base pairing and the concept of anti-parallel polarity. As stated in the context, the two DNA chains have opposite polarity, and the bases are complementary to each other.
Given the sequence 5'-ATGCATGCATGCATGCATGCATGCATGCATGCATGCATGC-3', the complementary sequence reading in the 3'–5' direction would be 3'-TACGTACGTACGTACGTACGTACGTACGTACGTACGTAC-5' (pairing Adenine with Thymine, and Guanine with Cytosine).
To write this in the requested 5'–3' direction, we simply reverse the above sequence. The final sequence is: 5'-GCATGCATGCATGCATGCATGCATGCATGCATGCATGCAT-3'
Explanation
The question requires identifying the complementary base pairs and arranging them according to the anti-parallel nature of the DNA double helix. The context explicitly states that the two chains have anti-parallel polarity (one is 5'→3', the other is 3'→5'). First, the complementary sequence is generated in the 3'→5' direction (A-T, T-A, G-C, C-G). Then, this sequence is flipped to present it in the standard 5'→3' format requested.
Solution Steps
Step 1: Determine the complementary bases for the given strand (A pairs with T, T with A, G with C, C with G) to generate the sequence 3'-TACGTACGTACGTACGTACGTACGTACGTACGTACGTAC-5'.
Step 2: Reverse the polarity of the derived sequence to write it in the 5' to 3' direction, resulting in 5'-GCATGCATGCATGCATGCATGCATGCATGCATGCATGCAT-3'.