Final answer:
The most stable DNA molecule among the given options is D) GCGTGCAC CGCACGTG, due to its high number of GC pairs, which form stronger triple hydrogen bonds compared to AT pairs.
Step-by-step explanation:
The stability of a DNA molecule is influenced by the number of hydrogen bonds between the nucleotides that make up the double helix. Adenine (A) pairs with thymine (T) with 2 hydrogen bonds, and guanine (G) pairs with cytosine (C) with 3 hydrogen bonds. More GC pairs mean a more stable DNA molecule since they provide more hydrogen bonds. Option D) GCGTGCAC CGCACGTG is the most stable DNA molecule listed because it has the highest number of GC pairs. The GC pairs create a stronger bond due to their triple hydrogen bond nature compared to the double hydrogen bond in AT pairs.
Therefore, for a complementary strand of DNA to GCTTATAT as in question 17, option c. CGAATATA would be the correct match since each nucleotide is complementary to the original strand, following the base-pairing rules (C with G, A with T). Similarly, if a DNA strand contains the sequence 5'-ATTCCGGATCGA-3', the complementary strand would have the sequence 3'-TAAGGCCTAGCT-5' as in 9.C.