Problem 8 - AP Psychology Premium Prep 2021

Question

BamHI is a restriction enzyme derived from Bacillus amyloliquefaciens that recognizes short palindromic sequences in DNA. When the enzyme recognizes these sequences, it cleaves the DNA. What purpose would restriction enzymes have in a bacterium like Bacillus? (A) They are enzymes that no longer have a purpose because evolution has produced better enzymes. (B) They destroy extra DNA that results from errors in binary fission. (C) They protect Bacillus from invading DNA due to viruses. (D) They prevent, or restrict, DNA replication when the cell isn't ready to copy its DNA.

Step-by-Step Solution

Answer

The correct answer is (C) Restriction enzymes, like BamHI, protect the bacterium Bacillus from invading DNA due to viruses.

Step 1: Understand Restriction Enzymes

Restriction enzymes, also known as restriction endonucleases, are enzymes that recognize and cut specific DNA sequences. They are found in bacteria and form part of the bacterial defense mechanisms against viruses called bacteriophages.

Step 2: Analyze Answer Option A

Option A suggests that restriction enzymes no longer have a purpose because evolution has produced better enzymes. However, this is not true as restriction enzymes continue to play an essential role in the bacterial defense mechanism against viruses. Therefore, option A is incorrect.

Step 3: Analyze Answer Option B

Option B suggests that restriction enzymes destroy extra DNA produced due to errors in binary fission. Restriction enzymes do cut DNA sequences, but their primary purpose is not to correct errors in binary fission. Rather, their primary function is related to defense against foreign DNA, such as virus. Therefore, option B is incorrect.

Step 4: Analyze Answer Option C

Option C proposes that restriction enzymes protect Bacillus from invading DNA due to viruses. This is consistent with our understanding of the function of restriction enzymes, which play a crucial role in bacterial defense mechanisms against bacteriophages by recognizing and cutting their DNA. Therefore, option C appears to be correct.

Step 5: Analyze Answer Option D

Option D claims that restriction enzymes prevent or restrict DNA replication when the cell isn't ready to copy its DNA. While it is true that cells need to control DNA replication, restriction enzymes' primary function is not associated with regulating bacterial DNA replication. Their main purpose is related to defense against foreign DNA. Therefore, option D is incorrect.

Step 6: Conclusion

Based on the analysis of the given options, the correct answer is option C: Restriction enzymes, like BamHI, protect the bacterium Bacillus from invading DNA due to viruses.