 Genome evolution by chromosomal rearrangements. Chromosomal rearrangements is a type of chromosome abnormality, involving a change in the structure of the chromosome. Such changes may involve several different classes of the events that can be in the form of deletions, duplications, inversions and translocations. So chromosomal rearrangements can be in different forms. It can be in the form of deletions. There are small fragment of the chromosome or the DNA can be deleted. It can be in the form of duplications, certain fragment is duplicated. It can be in the form of inversions that a small fragment of DNA of the chromosome is inversed and translocations movement from movement between two segments of the chromosomes. So these are different types of the classes. Chromosomal rearrangements caused by a breakage in DNA double helix at two different locations followed by a rejoining of the broken ends at different places that actually produce a new chromosomal arrangement. Instead of joining the broken ends at the actual position from where the DNA were broken, they joined to different places instead of the original one. So that actually produces chromosomal rearrangements. Some regions of the genome are more prone to rearrangements than other. Thus, they are source of the evolution. This instability is usually due to the susceptibility of these regions to misaligned during DNA repair. Means those regions, they are more susceptible to be misaligned when there is a repair mechanism in case of DNA. Regulations frequently occur when a population becomes fixed for one or more chromosomal rearrangements. That actually reduces the fitness of the previous species. The example is of humans and mouse. Approximately 160 million years ago, mouse and human separated from each other, probably due to the chromosomal rearrangements. Many chromosomal rearrangements have been occurred in the past. Here is the diagram where we can do a comparison between the human genome and the genome of the mouse. These are the chromosomes of mouse, mouse chromosomes from 1 up to 19, 1 up to 19 and X chromosomes. According to homology with human chromosomes 1 to 20 and X, these are the human chromosomes and here is the X chromosome. If we do a comparison between the human chromosomes and the mouse chromosome, this is the color for chromosome number 1 of the humans. We can see that this color matches with chromosome 1. Here is the fragment then with chromosome 3 and with chromosome 4. Human chromosome 1 has actually homology with mouse chromosomes 1, 3 and 4. Another example can be of chromosome 2 that we can see here. In case of human chromosome 2, it has homology with the P arm or with the disfragment of the chromosome number 1 of the mouse with the chromosome 2 of the mouse and some parts of chromosome 11 and 12 of the mouse. So these are the comparison. Just take another example of the chromosome 3. In case of human chromosome 3, we can see that it has homology with chromosome 3 here with the mouse and it has homology here with the chromosome 16. So here we can see that approximately 160 million years ago the mouse and the humans they separated from each other. Humans have 23 pair of chromosomes while on the other hand chimpanzee they have 24 pair of chromosomes. Divergence of human and chimpanzee from a common ancestor that is actually two ancestral chromosomes fuse to each other. We take another example about it. Here we can see that this is the human chromosome number 2 and these are the chromosome of chimpanzee. This is chromosome 12 of the chimpanzee and this is chromosome 13 of the chimpanzee. We can see that chromosome number 2 have homology with the chimpanzee chromosome 12. Here we can see that this fragment of the human that is P arm of the chromosome 2 of the humans it has homology with the chromosome number 12 of the chimpanzee. And here is the Q arm of the human chromosome number 2. It has the homology with the chromosome number 13 of the chimpanzee. So it can be hypothesized that chromosome number 2 of the humans evolved by the chromosomal rearrangements of chimpanzee chromosome number 12 and chimpanzee chromosome number 13. Comparative analysis between chromosome of humans and 7 mammalian species they have painted a hypothetical chromosomal evolutionary history. There is another example about the chromosomal rearrangements in case of human chromosome number 16 and in case of mouse chromosome number 7, 8, 16 and 17. We can see here that in case of human chromosome 16 this is the green color. This part has the homology with the chromosome number 7 of the mouse. This Q arm of chromosome number 16 of the human it has homology with chromosome number 8 of the mouse. This part that is a chromosome number 16 it has homology with the P arm towards the telomer has homology with each other. And here is the part that is present on chromosome number 17 of the mouse has homology towards the telomer end of the human chromosome number 16. So here we can see that in case of human chromosome 16 has emerged or evolved from four different chromosomes of the mouse that is chromosome number 7, 8, 16 and 17. If we conclude that what are chromosomal rearrangements some chromosomal regions are more prone to rearrangements than others and thus those regions they are the source of evolution.