MCAT Biological and Biochemical Foundations of Living Systems Practice Exam

The correct answer highlights the relationship between deoxyribose and phosphate groups in the structure of nucleic acids, particularly DNA. In nucleic acids, phosphodiester bonds are formed between the phosphate group of one nucleotide and the hydroxyl group on the deoxyribose sugar of another nucleotide. This connection creates a backbone that is essential for the structural integrity of nucleic acid strands.

In more detail, each nucleotide consists of a phosphate group, a sugar (deoxyribose in DNA or ribose in RNA), and a nitrogenous base. The formation of the phosphodiester bond occurs specifically at the 3' hydroxyl group of one sugar and the 5' phosphate of the next nucleotide, resulting in a long chain of nucleotides connected together. This bonded arrangement is what forms the backbone of DNA or RNA, giving the molecule its structural framework and enabling the storage of genetic information.

In this context, options mentioning ribose and uracil, phosphate groups and nitrogenous bases, or solely deoxyribose sugars do not accurately depict the nature of the phosphodiester bond, which explicitly involves both the sugar and the phosphate group in the linkage of nucleotides along the nucleic acid strand.