Nucleotide excision repair and photolyases would be beneficial for bacterial strains _________________.

Question

BlackTom AI · Accepted Answer

Photolyases directly reverse ultraviolet-induced cyclobutane pyrimidine dimers (CPDs), and nucleotide excision repair (NER) removes bulky, helix-distorting lesions such as those same UV-induced pyrimidine dimers—therefore both systems are especially useful for bacteria exposed to UV light.

1) Relevant knowledge points and concepts
- UV radiation (particularly UV-B/UVC) induces covalent bonds between adjacent pyrimidines (most commonly thymine–thymine), forming cyclobutane pyrimidine dimers and 6-4 photoproducts that distort the DNA helix and block replication/transcription.
- Photolyases perform light-dependent “photoreactivation”: an enzyme binds the dimer and, upon absorbing blue/near-UV light with its chromophore and reduced FAD cofactor, transfers an electron to split the dimer, restoring two normal pyrimidines.
- Nucleotide excision repair is a multienzyme pathway that recognizes bulky helix-distorting lesions, excises an oligonucleotide segment containing the lesion, and fills/seals the gap.

2) Step-by-step reasoning process
- UV exposure → formation of pyrimidine dimers that impede DNA function.
- Photolyase mechanism: enzyme binds dimer → absorbs light → electron transfer breaks cyclobutane ring → lesion reversed without cutting backbone.
- NER mechanism in bacteria (Uvr system): UvrA+UvrB detect distortion → UvrC makes dual incisions flanking lesion → UvrD helicase removes the oligonucleotide fragment → DNA polymerase I synthesizes replacement nucleotides → DNA ligase seals nick.
- Both mechanisms therefore prevent mutations and restore normal DNA after UV damage.

3) Intermediate steps shown (NER enzymes): recognition (UvrA/UvrB) → incision (UvrC) → excision (UvrD) → resynthesis (DNA pol I) → ligation.

4) Why the correct answer is correct
Both photolyases and NER specifically target and repair the bulky, covalent pyrimidine dimers produced by UV light. Photolyase provides a rapid light-dependent reversal; NER provides a light-independent excision and replacement pathway—complementary defenses against UV damage.

5) Why other options are incorrect
- “With oxidized guanine (G) bases”: oxidized bases like 8-oxoG are primarily repaired by base excision repair (glycosylases), not photolyase/NER.
- “With extensive DNA strand breaks”: strand breaks are fixed by recombinational repair or end-joining processes and require different enzymes (e.g., RecA-mediated homologous recombination), not photolyase.
- “Lacking DNA polymerase”: absence of DNA polymerase prevents gap filling after excision; photolyase also requires light and cannot substitute for polymerase functions—these repair systems do not correct the fundamental problem of missing polymerase activity.

Conclusion: Photolyases and NER are most beneficial for bacterial strains exposed to UV light; this matches the provided correct answer: exposed to UV light.

Nucleotide excision repair and photolyases would be beneficial for bacterial strains _________________. 单项选择题

类似问题

Base excision, nucleotide excision and mismatch repair are strategies the cell uses to correct certain DNA mutations. Which of the following enables these repair mechanisms to occur accurately?

Which of the following statements is true of DNA damage?

Which of the following is not true about DNA double strand breaks?

Question at position 12 What binds cut DNA and retains it in protein-DNA complex?XRCC4 with DNA ligase IVKu70/80TdTArtemisRAG1/2

You have the following mutation in the DNA: What caused this mutation and how would you fix it?

Which of the following mechanisms can be used when no template DNA is available to repair DNA damage? (1 mark)

DNA repair mechanisms _______________.

Direct DNA repair may work on mutations that arise as a result of exposure to which type of chemical mutagen?

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单