Chapter 3 Practice

Reading notes/Potential Exam Questions for Chapter 3: Genomics

Nucleosides, Bases and Nucleotides, Structures and names:

  1. Draw the purine and pyrimidine bases, the nucleosides and the nucleotides.
  2. Draw the correct hydrogen bonds between G-C and A-T

DNA Structure:

  1. What are Chargaff's rules?
  2. Why do nucleotide bases absorb UV light (260 nm)?
  3. Why does single stranded DNA absorb more light at 260nm?
  4. The Tm for DNA with more GC is higher than the Tm for DNA with more AT. Why?
  5. What factors influence the Tm?
  6. Describe the double helix of B DNA, A and Z DNA.

Bacterial DNA is circular, so supercoiling means the "circle" is looped around itself. For linear eukaryotic DNA, supercoiling occurs when the DNA wraps around histones(proteins). The DNA twisted around the histones must be unwound (negative supercoiling) with topoisomerases before it can be copied or transcribed.

  1. What is supercoiling? Why is it essential?
  2. What two factors add up to give the linking number? (Describe them.)
  3. What reaction does topoisomerase I catalyze?
  4. What reaction does topoisomerase II catalyze?
  5. Why are topoisomerase II inhibiters used to treat cancer?


  1. What are the differences between DNA and RNA?
  2. Give some examples of unconventional DNA and RNA base pairing.
  3. What happens when RNA is exposed to a basic solution?
  4. What types of structures exist for RNA?
  5. What are the functions of RNA?


  1. How much is DNA condensed in a cell (what factor).
  2. Describe each of the following: linear DNA, Nucleosomes, Chromatin, Looped Chromatin, Condensed coils of chromatin, Chromosome
  3. Define euchromatin and heterochromatin
  4. What is the centromere?
  5. What are telomeres?


  1. What is a promoter? What has to bind to it for the DNA to be transcribed?
  2. What is the "coding region"
  3. Describe: intron, exon, 5'UTR


  1. What is the NCBI?
  2. How did they determine the mutation that is responsible for Hutchinson-Gilford Progeria?
  3. The most common mutation for this disease is a single base change of C > T, how does this mutation cause the disease?
  4. How does a C become a T?
  5. What is a SNP?
  6. What is a STR?
  7. How are SNPs and STRs used in Forensics?
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