The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage? a. nuclease, DNA polymerase, DNA ligase b. telomerase, primase, DNA polymerase c. telomerase, helicase, single-strand binding protein d. DNA ligase, replication fork proteins, adenylyl cyclase

Verified step by step guidance

1. Identify the type of DNA damage described: The problem states that adenine loses an amino group to form hypoxanthine, which then pairs incorrectly with thymine. This type of damage is a form of deamination, which alters the base pairing in DNA.
2. Understand the repair mechanism needed: The repair of such damage generally involves base excision repair (BER). This process first requires the recognition and removal of the incorrect base, followed by the filling in of the correct base and sealing of the DNA backbone.
3. Analyze the options given: Option (a) lists nuclease, DNA polymerase, and DNA ligase. Nuclease can excise the damaged base, DNA polymerase can fill in the correct nucleotide, and DNA ligase can seal the phosphate backbone.
4. Eliminate other options: Option (b) includes telomerase and primase, which are not involved in DNA repair processes. Option (c) also includes telomerase, which is irrelevant for DNA repair. Option (d) includes DNA ligase but lacks the necessary enzymes for initial recognition and excision of the damaged base.
5. Conclude the correct answer: Based on the understanding of the base excision repair mechanism, the correct combination of proteins to repair the deamination of adenine to hypoxanthine is nuclease, DNA polymerase, and DNA ligase, which corresponds to option (a).

Key Concepts

DNA Repair Mechanisms

DNA repair mechanisms are essential processes that correct damage to the DNA structure, ensuring genomic stability. One common type of repair is base excision repair, which specifically targets and removes damaged bases, such as hypoxanthine, before replacing them with the correct nucleotides. This process involves several proteins, including nucleases that cut the DNA, DNA polymerases that synthesize new DNA, and DNA ligases that seal the nicks in the DNA backbone.

Role of Nucleases

Nucleases are enzymes that cleave the bonds between nucleotides in nucleic acids. In the context of DNA repair, nucleases are crucial for recognizing and excising damaged or incorrect bases, such as hypoxanthine. By removing these bases, nucleases initiate the repair process, allowing other enzymes like DNA polymerase to fill in the gaps with the correct nucleotides, thus restoring the integrity of the DNA strand.

Function of DNA Polymerase

DNA polymerase is an enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand during DNA replication and repair. In the repair context, after a damaged base is excised by a nuclease, DNA polymerase plays a critical role in inserting the correct nucleotide to replace the missing or damaged one. This ensures that the genetic information is accurately maintained and passed on during cell division.