In this video, we're going to begin our lesson on DNA repair. And so it turns out that DNA replication is not always a perfect process. And so most of the time, DNA replication works exactly as it's supposed to, but occasionally DNA replication will not work perfectly, and it will create errors. And so base pairing errors can occur during DNA replication. And so for example, we know that a's or adenines are normally supposed to be paired up with T's or thymines. But if there's a base pairing error that occurs, then this a might be base paired with a c or cytosine instead of being base paired with the t thymine like what it's supposed to be. And so these base pairing errors can occur, and these errors occur 1 out of every 100000 base pairs, which at first glance might seem like a really low error rate, only one error out of a 100000 base pairs, but it's actually a relatively high error rate considering that there's a lot of DNA and the DNA replication needs to occur often. Now unrepaired errors can actually result in permanent mutations, And these permanent mutations in the DNA can actually lead to diseases like cancer, for example. And so down below in our image, in our example image, we're showing you how these DNA errors can kind of resemble typos in a resume. And so in this cartoon that we're showing you down below, this guy over here is coming in for an interview for a job position, and he hands his resume over to the big boss over here. And the boss is reading through the resume and he says, says here that you're a professional booger. And this guy's trying to clear it up. He's like, oops, I meant blogger. And so that's a typo that's in the resume. And that is gonna greatly affect this guy's chances of landing this job position. And so mutations, these unrepaired errors in the DNA kind of resemble typos in a resume. And so they can actually significantly change the end result of the the product that's supposed to be encoded by the DNA. And so, these unrepaired errors or mutations can lead to diseases like cancer. And so this here concludes our brief introduction to DNA repair, and we'll be able to talk a little bit more as we move forward in our course. So I'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 100000 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 proof reading 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.