Here's how to represent a portion of DNA with the sequence GAC and its complementary strand, showing structural formulas and base pairing:---Step 1: Write the original strand (5' to 3')Guanine - Adenine - CytosineG – A – C---Step 2: Determine the complementary bases (3' to 5')Guanine (G) pairs with Cytosine (C)Adenine (A) pairs with Thymine (T)Cytosine (C) pairs with Guanine (G)So the complementary strand is:C – T – G---Step 3: Draw base pairing with hydrogen bondsHere's a simplified representation with hydrogen bonds shown as dashed lines (===):5' - G === C - 3' | | A === T | | 3' - C === G - 5'