THE MOLECULAR BASIS OF INHERITANCE
STRUCTURE OF NUCLEIC ACIDS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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120 adenine and 120 uracil molecules
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120 thymine and 120 adenine molecules
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120 cytosine and 120 thymine molecules
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240 adenine and 240 cytosine molecules
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Detailed explanation-1: -A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines.
Detailed explanation-2: -The total number of nucleotides would be 120 × 4 = 480.
Detailed explanation-3: -According to Chargaff’s rules, the amount of adenine is always equal to that of thymine, and the amount of guanine is always equal to that of cytosine i.e A = T = 120 and G = C = 120, therefore, the total no. of nucleotides would be 120×4=480. Q.
Detailed explanation-4: -Answer and Explanation: A double-stranded DNA molecule with 20% thymine would contain 30% guanine. Erwin Chargaff determined that species have almost equal levels of adenine and thymine, and guanine and cytosine. This is due to the complimentary nature of these bases (i.e., they typically only bond with each other).