One strand of a DNA double helix reads, from its 5' end to its 3' end, A T G C C A. What is the sequence of the complementary strand, listed from its own 5' end to its 3' end?

Core Concept

Base pairing rules fix every partner: adenine pairs with thymine and guanine pairs with cytosine in DNA. The partner strand runs antiparallel, so reading it from its own 5' end means traveling backward along the template while swapping each base for its complement. Working through the template from 3' toward 5', the complements appear in the order T, G, G, C, A, T. Antiparallel alignment is what lets paired bases meet properly inside the uniform-width double helix.