Question

Indicate whether each of the following statements about DNA repair is true or false.

a. Many DNA polymerases have 3'-to-5'exonuclease activity that allows "proofreading" and replacement of incorrect bases.
b. "Proofreading" effectively eliminates all errors during DNA replication.
c. Error correcting mechanisms during DNA replication cause cells to accumulate errors at a higher rate, which leads to higher levels of deleterious or lethal mutations. In addition to errors that occur during DNA replication, cells are constantly exposed to agents that can damage DNA, such as UV light, X-rays, and chemicals in the environment.
d. Agents that damage DNA can lead to mutations
e. Any agent that decreases the number of mutations below background levels is called a mutagen.
f. Cells cannot escape exposure to mutagens, but they have evolved systems that enable them to repair all of the damage.
g. All cells that have been examined show multiple pathways for repairing damaged DNA and for reversing errors that occur during replication.
h. Although most mutations are harmful, some may be beneficial.

Answer 1

True and false statements about DNA repair pertain to the activity of DNA polymerases, the ability to eliminate errors, the effect of repair mechanisms on mutation rates, the potential for environmental agents to cause DNA damage, definitions of mutagens, the capacity of cells to repair damage, and the nature of mutations.

Step-by-step explanation:

Indicate whether each of the following statements about DNA repair is true or false:

• a. True: Many DNA polymerases have 3'-to-5' exonuclease activity that allows "proofreading" and replacement of incorrect bases.
• b. False: "Proofreading" effectively reduces errors during DNA replication, but it does not eliminate all errors. Some errors can still persist after proofreading mechanisms and subsequent repair mechanisms have acted.
• c. False: Error correcting mechanisms during DNA replication actually decrease the rate at which cells accumulate errors, lowering the levels of deleterious or lethal mutations.
• d. True: Agents that damage DNA, such as UV light, X-rays, and chemicals, can lead to mutations.
• e. False: An agent that decreases the number of mutations below background levels is called an antimutagen, not a mutagen.
• f. False: Though cells have evolved systems to repair damage, they cannot repair all of the damage. Some damage can persist as mutations.
• g. True: All cells that have been examined show multiple pathways for repairing damaged DNA and for reversing errors that occur during replication.
• h. True: Although most mutations are harmful, some may be beneficial and contribute to genetic diversity and evolution.