In double stranded DNA, the total amount of purines always equals the total amount of pyrimidines because
Correct answer: D. each base pair contains one purine and one pyrimidine
- A. the sugars bond only to purines
- B. phosphate groups pair with pyrimidines
- C. hydrogen bonds form only between bases of equal size
- D. each base pair contains one purine and one pyrimidine
Explanation
Adenine and guanine are the purines, thymine and cytosine the pyrimidines, and every pair across the helix matches one of each. This is why Chargaff found A plus G equals T plus C, and it keeps the two strands a constant distance apart.
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About Classification of Biological Molecules
Biological molecules are classified as carbohydrates, lipids, proteins and nucleic acids, with water, minerals and vitamins also supporting cellular processes. The key distinctions involve their monomers, chemical bonds, structures and functions, including glucose and starch, fatty acids and triglycerides, amino acids and polypeptides, and nucleotides in DNA and RNA.
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