THE MOLECULAR BASIS OF INHERITANCE
DNA MAKES RNA MAKES PROTEIN
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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adenine molecules in DNA is about equal to the percentage of guanine molecules.
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pyrimidines in DNA is about equal to the percentage of purines.
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purines in DNA is much greater than the percentage of pyrimidines.
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cytosine molecules in DNA is much greater than the percentage of guanine molecules.
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Detailed explanation-1: -According to Chargaff’s rule, the number of purines and pyrimidines exist in ratio 1: 1. This is so because purines bond with pyrimidines to form nucleotides hence in a double-stranded DNA, the number of purines is equal to the number of pyrimidines.
Detailed explanation-2: -Human DNA is 30.9% A and 29.4% T, 19.9% G and 19.8% C. The rule constitutes the basis of base pairs in the DNA double helix: A always pairs with T, and G always pairs with C.
Detailed explanation-3: -According to Chargaff’s rule in a DNA molecule A = T and G = C and A + G + C + T = 100%. Here cytosine (C) is 18% hence G = 18% ∴ A + T = (100 – 36)% ∴ A + T = 64% ∴ A = 32% Q. In a double stranded DNA molecule, the percentage of cytosine is 18.
Detailed explanation-4: -Approximately equal amounts of purines and pyrimidines are required to form either DNA or RNA. It’s worth noting there are exceptions to the classic Watson-Crick base pairs. In both DNA and RNA, other configurations occur, most often involving methylated pyrimidines. These are called “wobble pairings."