When a double-strand DNA break occurs in a eukaryotic cell, it may be repaired by either nonhomologous end joining or homologous recombination. How do these different repair mechanisms lead to potentially different outcomes?

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Hi everyone welcome back. Here's our next problem. It says maintaining the integrity of the genome is achieved through the well known cellular defense process. Known as we've got answer choices of a proof reading. Be DNA repair see, transformation and D. Both A. And B. So let's keep in mind that we have the possibility that both A. And B. Can be correct. So we look at choice A proof reading. Well proof reading is that process by which the newly synthesized DNA strand as bases are added. D. N. A. Polymerase comes along and checks each base on the new strand. If it's not correct if it's a mismatch, it actually moves backward exercises and replaces the erroneous base. So proof reading involves the newly synthesized strand and prevents errors as part of the replication process. So this is an important part of maintaining the integrity of the genome as it prevents errors when DNA is being replicated. So Choice A. Is correct. But again, since we have that possibility that our answer might be both A. And B. I'm just going to mark it as correct but not selected as the answer yet. Choice B. Is DNA repair. And DNA repair occurs by several different mechanisms that repair damage that occurs after replication to D. N. A. In the cell that prevents errors going on as cells grow and divide. So DNA repair. Several different mechanisms occurs uh to repair D. N. A damage. So either replacing damaged bases or in the most extreme cases when there's large lesions in the D. N. A. Skipping over those areas. But again very important to maintaining the integrity of the genome. Since it prevents errors in the D. N. A. As the cells grow and divide that could be disastrous. So Choice B also an important part an important cellular defense process. So we see that our answer then is Choice D. Both A and B. But to be thorough we'll look at choice C. Choices transformation transformation. In the context of molecular biology and genetics is the process by which a cell is modified through direct absorption and assimilation of external genetic material. So we'll just write that down. That process is used to create transgenic bacteria. For example when the researcher has a gene that gets introduced into the cell by a process of transformation that external genetic material is absorbed and then assimilated into the bacterial genome. But it's not part of maintaining the integrity of genome. It's actually an artificial alteration of the genome to produce the desired result. That's why Choice C. Is not our correct answer. So again, maintaining the integrity of the genome is achieved through the well known cellular defense process of de both A and B. Proof reading and DNA repair. See you in the next video

When a double-strand DNA break occurs in a eukaryotic cell, it may be repaired by either nonhomologous end joining or homologous recombination. How do these different repair mechanisms lead to potentially different outcomes?

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Key Concepts

Double-Strand DNA Breaks

Nonhomologous End Joining (NHEJ)

Homologous Recombination (HR)