Homologous Recombination

DNA can break and rejoin in a process called recombination. When DNA molecules share a similar sequence, they are said to be homologous to one another. The mutual exchange of corresponding genetic material between two such DNA molecules is called homologous recombination. This process begins when one strand of each DNA helix breaks and partially invades the other molecule, forming an X-shaped structure known as a Holliday junction. Next, winding and unwinding of the DNA results in branch migration, or leftward movement of the Holliday junction. One strand of each interchanging DNA segment can then be nicked, or cut by an endonuclease enzyme, and joined to the opposite molecule to produce two recombinant DNA double helices. This separates, or resolves, the two DNA molecules and completes the homologous recombination process.

Question 1: The process of homologous recombination involves?
  1. Exchange of genetic material
  2. DNA breakage and rejoining
  3. Formation of a Holliday junction
  4. All of the above


Answer 1

Answer (d) - All of the above

Question 2: What is the process called when one strand of each DNA helix breaks and partially invades the other molecule to form an X-shaped structure?
  1. DNA replication
  2. Branch migration
  3. Holliday junction
  4. All of the above


Answer 2

Answer (c) - Holliday junction

Question 3: Which enzyme nicks DNA strands to produce two recombinant DNA double helicies
  1. DNA polymerase
  2. DNA helicase
  3. DNA endonuclease
  4. DNA ligase


Answer 3

Answer (c) - DNA endonuclease