If the cytosine in the sequence 5ʹ-GAATGCATG-3ʹ is deaminated and unrepaired, what sequence could be expected in the daughter strand?

If the cytosine in the sequence 5ʹ-GAATGCATG-3ʹ is deaminated and unrepaired, what sequence could be expected in the daughter strand?

• A. 5ʹ-CTTACATAC-3ʹ
• B. 5ʹ-CATACATTC-3ʹ
• C. 5ʹ-CATGCATTC-3ʹ
• D. 5ʹ-CTTACGTAC-3ʹ

Answer: (B)

When cytosine is deaminated, it is converted into uracil. In the context of DNA, this can lead to a base-pairing change during replication. The original sequence provided is 5ʹ-GAATGCATG-3ʹ. The cytosine in this sequence is located in the positions of the core base pairs. After deamination, the cytosine in the original strand may pair with adenine instead of guanine during DNA replication, leading to a change in the complementary strand sequence. Therefore, the complementary strand that would be synthesized would replace the previous pair with the newly deaminated pair. Looking at the options provided, the only one that incorporates adenine instead of guanine, reflecting the effects of the deamination of cytosine, is 5ʹ-CATACATTC-3ʹ, which accounts for this mispairing during the DNA synthesis process. This is the appropriate and accurate sequence that one would expect in the daughter strand following the unrepaired deamination of cytosine in the original sequence.

When cytosine is deaminated, it is converted into uracil. In the context of DNA, this can lead to a base-pairing change during replication. The original sequence provided is 5ʹ-GAATGCATG-3ʹ. The cytosine in this sequence is located in the positions of the core base pairs.

After deamination, the cytosine in the original strand may pair with adenine instead of guanine during DNA replication, leading to a change in the complementary strand sequence. Therefore, the complementary strand that would be synthesized would replace the previous pair with the newly deaminated pair.

Looking at the options provided, the only one that incorporates adenine instead of guanine, reflecting the effects of the deamination of cytosine, is 5ʹ-CATACATTC-3ʹ, which accounts for this mispairing during the DNA synthesis process. This is the appropriate and accurate sequence that one would expect in the daughter strand following the unrepaired deamination of cytosine in the original sequence.