Structure and function of genetic materials — A/L Biology

How do I practise Structure and function of genetic materials?

1 question with a worked solution

1. In a double-stranded DNA sample, adenine constitutes 28% of the total nitrogenous bases. What percentage of the bases is cytosine?
   1. A) 22%
   2. B) 28%
   3. C) 24%
   4. D) 44%
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   Correct answer: A) 22%

   According to Chargaff's rules for double-stranded DNA: %A = %T = 28%, so A + T = 56%. The remaining bases G + C = 100% - 56% = 44%. Since %G = %C, cytosine is 44% / 2 = 22%.

   Show worked solution

   Step 1: Apply Chargaff's rule: A = T = 28%. Step 2: Total A + T = 28% + 28% = 56%. Step 3: Total G + C = 100% - 56% = 44%. Step 4: Since G = C, Cytosine % = 44% / 2 = 22%. Answer: 22%.
   Modelled on: the A/L Biology examination pattern

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Where does Structure and function of genetic materials fit in the syllabus?

Year 1 · Term 2