in this video, we're going to begin our lesson on mutations, and so mutations are defined as permanent changes and the DNA sequence of an organism. And so these mutations, these permanent changes in the DNA sequence are very, very important. And that is because mutations in the DNA these changes in the DNA can actually impact the RNA via transcription. And, of course, if it can impact the R Navy a transcription, that means that these mutations can also impact proteins via translation. And so these changes in the DNA ultimately can have ah, widespread impact on the DNA, ultimately the RNA and then, ultimately the proteins. Now these mutations, they can either be harmful, meaning that they would reduce the chance of the organisms survival. They could also be beneficial, meaning that they improve the chances of the organism survival. Or they could also be neutral, meaning that they do not have an impact on the organism survival. And so, in terms of their impact and result, mutations can vary in their impact and result, and it depends on the specific scenario and the specific mutation. Now, mutations can actually occur either naturally through natural processes that occur within the cell or the mutations can actually be induced by environmental factors or chemical factors that air called Mu Jin's, which are chemical agents that can induce mutations. Now mutations themselves are going to be largely responsible for the tremendous diversity that is found amongst living organisms. And so the reason that there are so many different types of living species is because the accumulation of mutations on other features throughout a very, very long periods of time. And so this year concludes our brief introduction to mutations, and in our next lesson, video will be able to talk about different types of mutations, so I'll see you all in that video.
Types of Mutations
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in this video, we're going to be talking about the different types of mutations. And so it turns out that there are several different types of mutations, including the following mutations that we're going to talk about down below in our image. Now, first recall from our last lesson video that a mutation is a permanent change in the DNA sequence of an organism. However, a mutation, a change in the DNA can consequently lead to changes in the RNA, which can lead to changes in the protein or the amino acid sequence. And so here in this image were on Lee showing you the normal sequence for the m r N A. The messenger are in a and the normal sequence for the poly peptide. And so this would be the sequences of the Mara and the poly peptide under normal conditions, when there is no mutation and so down below in our image, what we're showing you are mutations that occur to this normal sequence. And so we've got the mutations grouped as either being point mutations, also known as substitution. Over here on the left hand side of our image, our point mutations. And then we've got the other set of mutations that are known as frame shift mutations and those air over here on the right hand side of our image. So we're going to start off with the point mutations, which are also known as substitution. And so the point mutations or the substitution. These are going to be involving the change of just one single nucleotide, uh, in the DNA. And so they're going to be a substitution of one nucleotide for another nuclear tied. Now there are three different types of point mutations that we're going to be talking about the first type of point mutation that you should know. It's called the silent mutation, and the reason that it's called the silent mutation is because if you're just looking at the the amino acid sequence or the poly peptide chain, you wouldn't be able to tell that there was a mutation. And that's because silent mutations have no effect on the amino acid sequence. But there is still a change of one nucleotide in the DNA and in the Army. But that one change in the DNA and the DNA that one nucleotide change in the DNA of the Arnie has no effect no impact on the amino acid sequence. And so what you'll notice is looking at the silent mutation. The poly peptide sequence is exactly as it is in the normal situation. There's no change in the poly peptide sequence in silent mutations. However, there still is the change of one nucleotide notice that in this code on, uh, in the mutated one down below, it has a code on of G. C. But the normal one is G A. And so the a nucleotide is being swapped for the sea nucleotide, and that is a mutation. But because this mutation does not change the amino acid sequence, it's a silent mutation. Now, the next type of point mutation that we're going to talk about is called a miss since mutation. Now, the Miss Sense mutation is a point mutation. So there's going to be a change of just one nuclear type. But this time the change of one nucleotide actually will change one amino acid. And so the change of just one amino acid is characterized by Miss Sense mutation. And so what you'll notice here in this image is that there is one nucleotide being changed. Uh, the it's this code on says C C A. And so the code on up above says, See you a And so the U is being swapped for a C. And normally there is a loose seen or L eu amino acid at this position. But in the minutes since mutation down below, it leads to a pro lean amino acids. So there is a change of the amino acid here, and so again, changing just one amino acid is characteristic of the miss since mutation. Now, the third and final type of point mutation that we're going to talk about is called the nonsense mutation. And the nonsense mutation is characterized by having the introduction of a premature stop coat on. And so there is just going to be the change of just one nucleotide and that change of one nucleotide changes the code on to a stop coat on, and it will prematurely cut the amino acid change short. And so notice that this, uh, amino acid chain is only just gonna have one amino acid in it because it is being cut short by this mutation that creates a premature stop coat on, and so you can see the change here Instead of having g a n. The code on the first G of the code on has changed to a U down below and the mutation and that u G A code on is a stop coat on. And so that's the introduction of a premature stop coat on is characterized by a nonsense mutation. And so that's it for the point mutations, silent mutation, Miss Sense mutation and nonsense mutation. So now we're going to shift over to the frame shift mutations. And so, as the frame shift mutation kind of implies, the code on reading frame is going to shift or change. And that means that the code on are going to be read in a different reading frame. And so, for example, there are two different types of frame shift mutations. The first is going to be an insertion. An insertion mutation is when there is the addition of one or more nucleotides that is going to cause a change in the reading frame of the code on reading frame. And so what you can see here is here we have an inserted nucleotide, a nucleotide that has been added to, uh, the sequence here. And so the addition of one nucleotide the insertion of this one nucleotide changes the reading frame of the code on reading frame of everything that is downstream of the mutation. And so, ultimately, frame shift mutations have the potential to cause amino acid changes to all of the amino acids that air downstream. And so you'll notice that Theoden Ishan of the G here, uh, in this fourth nuclear tide shifts over all of the other, uh, nucleotides, and that changes the reading frame. So it changes all of these corresponding amino acids and you can see the one amino acid here has just been shifted out since one has been inserted. Now, frame shift mutations can also occur as delusions. And so the deletion is going to be the removal of one or more nucleotides. And so the deleted nucleotide here is right here in this gap on. So you can see, uh, previously it was See you a. But the U is deleted. And so what that means is, it changes the code on reading frame. So we have a new coat on, which would be C a C instead of cuz. And that changes all of the code on reading frames. Again, it pushes the one coat on into a different uh, the one nucleotide into a different code on reading frame, and that can also change all of the amino acids downstream. And so what you can see here is that the point mutations are only gonna be changing just one nucleotide, substituting one nucleotide for another nuclear type. But there's no change in the code on reading frame, but with the frame shift mutation with an insertion or deletion that will change or shift the coat on reading frame. And so this year concludes our introduction to the different types of mutations, 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.
Which of the following mutations, occurring just after the start codon in the mRNA is likely to have the most serious effects on the polypeptide product?
Deletion of one codon.
Deletion of one nucleotide.
Insertion of three nucleotides.
Substitution of one nucleotide.
A nonsense mutation:
Causes an incorrect amino acid to be inserted into a polypeptide chain.
Causes synthesis of a polypeptide chain to be terminated prematurely.
Prevents the start of translation.
Only affects the mRNA code but does not affect the amino acid sequence of the polypeptide.