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.
