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Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172당신이 사용하는 게 아니라요?교과서 변경
11장, 문제 5

UV irradiation causes damage to bacterial DNA. What kind of damage is frequently caused and how does photolyase repair the damage?

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1
span>UV irradiation frequently causes the formation of pyrimidine dimers, particularly thymine dimers, in bacterial DNA. These dimers result from covalent bonding between adjacent thymine bases on the same DNA strand, disrupting normal base pairing and DNA replication.
span>Photolyase is an enzyme that specifically recognizes and binds to these pyrimidine dimers in the DNA.
span>Once bound, photolyase absorbs light, typically in the blue or near-UV spectrum, which provides the energy needed for the repair process.
span>The absorbed light energy is used by photolyase to break the covalent bonds between the thymine bases, effectively reversing the dimerization and restoring the normal base pairing.
span>This repair mechanism is known as photoreactivation, and it is a direct reversal of the DNA damage caused by UV irradiation.

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UV-Induced DNA Damage

Ultraviolet (UV) irradiation can cause various types of damage to DNA, with the most common being the formation of pyrimidine dimers, particularly thymine dimers. These dimers occur when adjacent thymine bases bond together, disrupting the normal base pairing and leading to replication errors if not repaired.
추천 영상:
가이드 코스
04:29
Induced Mutations

Photolyase Enzyme

Photolyase is a light-dependent enzyme that repairs UV-induced DNA damage, specifically pyrimidine dimers. It utilizes energy from visible light to cleave the bonds between the dimerized bases, restoring the DNA to its original state and allowing normal replication and transcription to occur.
추천 영상:
가이드 코스
01:45
DNA Proofreading

DNA Repair Mechanisms

DNA repair mechanisms are essential cellular processes that correct damage to DNA. In addition to photolyase, other repair systems like nucleotide excision repair (NER) and base excision repair (BER) exist, which recognize and remove damaged sections of DNA, followed by synthesis of new DNA to fill the gaps.
추천 영상:
가이드 코스
05:44
Repair Pathways
관련 실천
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What are the differences between a synonymous mutation, a missense mutation, and a nonsense mutation?

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In March 2011 an earthquake measuring approximately 9.0 on the Richter scale struck Fukushima, Japan. Several nuclear reactors at the Fukushima Daichii Nuclear Power Plant were damaged, and nuclear core meltdown occurred. A massive release of radiation accompanied damage to the plant, and 5 years later the incidence of thyroid cancer in children exposed to the radiation was determined to be well over 100 times more frequent than expected without radiation exposure. DNA damage and mutations resulting from radiation exposure are suspected of causing this increased cancer rate. What gene discussed in this chapter might be responsible for pausing the cell cycle of dividing cells long enough for radiation-induced damage to be repaired in cells?

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교과서 질문

For the retinal cancer retinoblastoma, the inheritance of one mutated copy of RB1 from one of the parents is often referred to as a mutation that produces a 'dominant predisposition to cancer.' This means that the first mutation does not produce cancer but makes it very likely that cancer will develop. Define the 'two-hit hypothesis' for retinoblastoma.

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교과서 질문

Ultraviolet (UV) radiation is mutagenic.

What kind of DNA lesion does UV energy cause?

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교과서 질문

In March 2011 an earthquake measuring approximately 9.0 on the Richter scale struck Fukushima, Japan. Several nuclear reactors at the Fukushima Daichii Nuclear Power Plant were damaged, and nuclear core meltdown occurred. A massive release of radiation accompanied damage to the plant, and 5 years later the incidence of thyroid cancer in children exposed to the radiation was determined to be well over 100 times more frequent than expected without radiation exposure. DNA damage and mutations resulting from radiation exposure are suspected of causing this increased cancer rate. Do you think it is possible that significant increases in the incidence of other types of cancer will occur in the future among people who were exposed to the Fukushima radiation? Why?

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