Question at position 26 The DNA of an organism is studied and found to contain 30% cytosine. Calculate the percentages of thymine and adenine in its DNA.30% thymine; 40% adenine40% thymine; 30% adenine60% thymine; 30% adenine20% thymine; 20% adenine60% thymine; 10% adenine

Question

BlackTom AI · Accepted Answer

In DNA, base pairing follows the rule that cytosine pairs with guanine and adenine pairs with thymine. If C is 30%, then G must also be 30%, since they pair up. That leaves 40% for A and T combined. Because A pairs with T and their amounts are equal in double-stranded DNA, A = T = 20% each. Now let's evaluate the answer options.

Option A: '30% thymine; 40% adenine' This contradicts the equal pairing of A and T and also contradicts the remaining 40% being split equally, so it is incorrect.

Option B: '40% thymine; 30% adenine' Similar issue: it assigns unequal, and incorrect values to A and T given the 20%/20% expectation. It does not reflect A = T = 20% each.

Option C: '60% thymine; 30% adenine' This option grossly overestimates thymine and again ignores the A = T requirement; it cannot be correct.

Option D: '20% thymine; 20% adenine' This matches the analysis: thymine is 20% and adenine is 20%, respecting C = G = 30% and A = T = 20%. It is consistent with base-pairing rules.

Option E: '60% thymine; 10% adenine' This option also violates the fundamental equal pairing of A and T and fails to reflect the remaining 40% after accounting for C and G; it is incorrect.

Together, the incorrect options fail to follow base-pairing rules or the equal distribution of complementary bases, while the correct option aligns with C = 30%, G = 30%, A = T = 20%.

Question at position 26 The DNA of an organism is studied and found to contain 30% cytosine. Calculate the percentages of thymine and adenine in its DNA.30% thymine; 40% adenine40% thymine; 30% adenine60% thymine; 30% adenine20% thymine; 20% adenine60% thymine; 10% adenine

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