Biochemistry Practice Questions

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Question 1

DNA is made up of many nucleotides, see the image below and clearly label the following feel free to use color the letters to indicate which is which.

  • a) 5’and 3’ends
  • b) deoxyribose (circle and label)
  • c) one phosphate group (circle and label)
  • d) bases (circle and label with their name)
  • e) one phosphodiester bond
  • f) the hydrogen atom that differentiates deoxyribose from ribose
  • g) the base that identifies this as DNA vs RNA
  • h) the chemical group on the base that defines it as a DNA base
  • i) which atoms in each base would participate in base paring.


 Question 2

DNA usually takes the B‐DNA form; Look up which turn of the helix this is and bases per turn, as well as inclination of base from the helix axis.

  • a) In the above 3 respects, how is B‐DNA different from Z‐DNA?
  • b) Label the figures below with a clear indication of where the bases per turn start and end.
  • c) Draw an axis for each helix
  • d) Draw the turn of each helix.


Question 3

Above is a stretch of DNA not drawn to scale of a chromosome in the process of replication. Address the pieces of missing information.

Question 4

The double helices shown below represent negatively supercoiled, positively supercoiled and relaxed DNA – not necessarily shown in this order. These are all B‐DNA molecules 312 bp long

  • a) label which is which
  • b) Indicate which topological transitions are catalyzed by DNA topoisomerase I and which are catalyzed by DNA topoisomerase II
  • c) Which molecule would be the least compact?


Question 5

  • a) What would be the sequence for the RNA primer? Note to which strand and where it will bind by rewriting it below. What makes the RNA primer?
  • b) what will be the structure of the final product?
  • c) What are the steps in this process?

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