In this video, we're going to begin our lesson on DNA repair. And so it turns out that the DNA replication process perfect process. Now although DNA replication usually is a perfect process that appropriately matches the nucleotides as they're supposed to, Occasionally, mistakes can occur or errors can occur, such as DNA base pairing errors. And these DNA base pairing errors can occur throughout the DNA replication process. And so for example, we know that a's or adenines are usually base paired with t's or thymines. However, if a mistake occurs or a DNA base pairing error occurs, then the a may accidentally be paired up with a c instead of the t. And so, these DNA base pairing errors can actually occur at a rate of about 1 out of 100000 base pairs, which at first glance may seem like a pretty low error rate. However, considering that there can be an enormous amount of DNA inside of a cell, millions if not billions of base pairs, and considering that DNA replication happens fairly frequently, this is actually a relatively high error rate. And so these unrepaired errors that occur can result in permanent mutations. And the mutations can potentially lead to diseases such as cancer. And so it's really important for a cell to be able to repair all of these errors and so moving forward, we're going to talk about some of these different, DNA repair mechanisms. But if we take a look at our example image down below, notice we have a cartoon here that is showing you how DNA errors somewhat resemble typos. And so in this cartoon, notice that we have 2 people. The person on the right over here is actually a candidate that's applying for a job. And on the left hand side over here, we have, a boss that is looking to hire someone. And so what you'll notice is that as this boss here is reading the resume from the candidate, the boss says, this says that you are experienced in ruining small businesses. And so notice that the candidate says, whoops, I meant to say running small businesses, not ruining. And so notice that even just a single typo, this I here exchange for an n, or vice versa there, that can make a huge difference in the interpretation. And so the same can occur with these mutations. Even just a single error, a single base pairing error could potentially lead to a very different result. And so, this here concludes our brief introduction to DNA repair and as we move forward, we'll get to learn a lot more. So stay tuned, and we'll see you in our next video.
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concept
DNA Proofreading & Repair Enzymes
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2m
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Video transcript
In this video, we're going to briefly introduce DNA proofreading and DNA repair enzymes. And so DNA polymerases actually have a proofreading ability. And so this proofreading ability is really just an ability that these DNA polymerases have to find and fix many of the errors or mistakes that might occur during DNA replication. And so the proofreading ability that these DNA polymerases have actually allows them to significantly reduce the error rate from 1 in 100 1,000 to just 1 in 10,000,000,000 base pairs, making mutations a lot less likely due to mistakes with DNA polymerases. However, they are still possible because 1 in 10,000,000,000 is still possible. Now other DNA repair enzymes on top of the DNA polymerase proofreading can actually also be involved with helping to correct errors that may not have been fixed by proofreading. And so down below in our image, what we're showing you is a little cartoon of a DNA polymerase over here proofreading the DNA sequence after replication. And so it says, looks like you made a typo here, and what this proofreading ability allows for is for fixing those errors and mistakes in the DNA. And so, again, that will reduce the error rate to just 1 in 10,000,000,000 base pairs, which is significantly lower and makes mutations due to errors in DNA replication much less likely. And so this here concludes our brief introduction to DNA proofreading ability and repair enzymes that can also help reduce error rates. And we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
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Problem
Problem
Researchers found a strain of E. coli bacteria that had mutation rates one hundred times higher than normal. Which of the following statements correctly describes the most likely cause of these mutations?
A
The single-stranded binding proteins were malfunctioning during DNA replication.
B
There were one or more mutations in the RNA primer.
C
The proofreading mechanism of DNA polymerase was malfunctioning.
D
The DNA polymerase was unable to add bases to the 3′ end of the growing DNA strand.