Question Video: Illustrating a Chromosomal Inversion Mutation Biology

The diagram provided shows a simplified outline of the different types of chromosomal mutations that can occur. Which diagram (1, 2, or 3) demonstrates an inversion mutation?

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Video Transcript

The diagram provided shows a simplified outline of the different types of chromosomal mutations that can occur. Which diagram, 1, 2, or 3, demonstrates an inversion mutation?

This question is asking us about chromosomal mutations. So what exactly is a chromosome anyway? Inside most of our cells is our DNA. Our DNA is organized on structures called chromosomes. These are long linear pieces of compacted DNA that contain a number of genes. We’re indicating these genes here as a few colored orange lines, whereas in reality there can be thousands of genes on a single chromosome. These genes provide the instructions our cells need to properly function. A chromosomal mutation is when the structure of this chromosome is somehow changed. This can cause problems for the cell because these mutations might have an impact on the genes contained within the chromosome.

There are several types of chromosomal mutations, duplications, deletions, and inversions. Let’s take a closer look and see how each of these can happen. To draw these, we’ll be labeling different segments of the chromosomes with different letters to help us see what impact these mutations have on the chromosome structure. In a duplication, a part of the chromosome is duplicated or copied. In this example, we now have two segments that contain the letter E. You’ll also notice that this makes the chromosome larger because it now includes extra genetic material. It also has two copies of all the genes that were contained in that region. This can increase production of those proteins, which can cause problems for the cell.

In a chromosomal deletion, a part of the chromosome is now missing. Now, this chromosome is missing genes that were in that region, which can also cause problems for the cell. Inversion mutations, which is what this question is asking us about, involve a segment of a chromosome breaking off then reattaching in the inverse orientation. We can see this here, how the section DEF is inverted to FED.

Now let’s turn our attention to the diagram on the left and see if we can figure out which of the three mutations represents a chromosomal inversion. Let’s make sure that we pay attention to these colored bands on each segment of the chromosomes. We can use these to help determine what happened to each mutated chromosome. In mutation 1, this section of the chromosome is missing. This is an example of a chromosomal deletion. We can also see a chromosomal deletion in mutation 3. In addition, we can also see these two sections duplicated in mutation 3. In mutation 2, we can see that these two bands have been inverted. Therefore, mutation 2 demonstrates an inversion mutation.

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