Structure of DNA and RNAAQA A-Level Biology: Mind map

Exam questions on Structure of DNA and RNA

1. Analysis of a sample of double-stranded DNA from a bacterium showed that 22 % of its bases were guanine.
   Explain why the percentage of adenine in the sample is equal to the percentage of thymine.2 marks
2. In a eukaryotic cell, DNA is held in the nucleus. A gene is copied into a molecule of messenger RNA (mRNA), which then moves to the ribosomes in the cytoplasm.
   Explain how the structure of mRNA makes it suitable for carrying genetic information from the nucleus to the ribosomes.2 marks
3. In the early twentieth century many scientists doubted that DNA carried the genetic code. A synthetic double-stranded DNA fragment, 10 base pairs long, contains 3 adenine-thymine base pairs and 7 cytosine-guanine base pairs.
   Suggest why many scientists doubted that DNA carried the genetic code.3 marks