Q.Describe the specific complementary base pairing in DNA: which bases pair with which, and how many hydrogen bonds hold each pair together?

UMP contains ribose sugar and is a ribonucleotide (RNA), not a deoxyribonucleotide.

A deoxyribonucleotide consists of a nitrogenous base + deoxyribose sugar + phosphate group, and is a building block of DNA. dAMP, dGMP, and dCMP (deoxy-Adenosine/Guanosine/Cytidine monophosphate) are all deoxyribonucleotides found in DNA.

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Chargaff's rule: A = T and G = C, so total purines = total pyrimidines, i.e. A + G = T + C — the answer is (c).

Chargaff's rule (Erwin Chargaff) states that in a double-stranded DNA:

• Amount of adenine = amount of thymine ($A = T$), and
• Amount of guanine = amount of cytosine ($G = C$). …