Recently, we have been working a lot with genetics and evolution, so for this post, we are going to combine the concepts to observe the similarities in DNA between multiple organisms, particularly through a beta globin gene that all of the organisms produce. To accomplish this, we used a program, Biology Workbench, to compare the genetic code of humans, chimps, goldfish, chicken, mice, and wallabies. The program highlighted the similarities between the codes in blue, the differences in black. The results are shown below.
By analyzing the data from the comparison of chimp DNA to human DNA, we see that the chimp has 600 base pairs while humans have 626. Similar nucleotides in both sequences are represented through blue asterisks, and are known as "conserved" nucleotides. By referencing the data from the human/chimp comparison, we see that the sequences have a 99% similarity. Because the sequences do have such a high similarity, it can be reasonably concluded that they would share a very similar protein structure as well. In contrast, the similarities between humans and chickens are remarkably lower at 57%. From this, we can expect humans to produce beta globin that is more similar to that of the chimp rather than the chicken. We can also see that the results achieved from this alignment support the results on evolutionary relationships, as anatomical structure and protein structure similarities connect relationships between chimps and humans.
The diagram below examines all of the species' sequences that were compared through the computer program. Because the species that were compared do not share a common ancestry, an unrooted tree diagram was used to compare the species. When viewing the diagram, you should understand that the closer the branches are to each other, the more closely related the species are, and conversely: the farther the distance, the farther the relativity.
As you can see, the two shortest "leaves" on the diagram belong to the human and chimp, and the both extend from the same branch. This means that they are the two most closely related species on the diagram. Conversely, the two species with the least relativity are the chicken and human, as they are the farthest apart on the diagram. Listed below are the other similarity percentages between humans and the other compared species.
Human:Chimp- 99%
Human:Chicken-57%
Human:Mouse- 79%
Human:Wallaby- 75%
Human:Goldfish- 63%
It is very interesting to see that even though there are few species even relatively close to humans, all of them lie above the 50 percentile in comparison of their DNA structure. This also shows that mammals in the rodent family are much closer to primates than other species.
While we have already discussed the unrooted tree diagram, it is also important to mention and demonstrate the use of a rooted tree diagram. While rooted tree diagrams are used to compare species that share a common ancestor, the animals we are comparing today do not, and thus we will leave that section of the diagram unlabeled. The rooted tree diagram does, however, allow us to see more clearly which species have descended through generations.
As you can see from the diagram, the goldfish is most closely related to the chicken while chimps and humans are most closely related to mice.
Homology is defined as a similarity in a feature that exists in two or more species due to descent from a common ancestor of the species. As we can see in this diagram, chimps and humans share the greatest homology with respect to the beta globin gene.
Another aspect of the diagram we should discuss are nodes. Nodes are branching points in the diagram that represent divergence fro a common ancestor. Based on the diagram above, we can conclude that chimps and humans have the most ancestral nodes, as they have diverged three times. This proves that both humans and chimps have adapted from their common ancestors. We can also determine that humans and chimps have diverged most recently, while the wallaby and mouse developed least recently. This can be determined based on the amount of nodes present in the diagram.
Now, let's try to imagine what the order would be if a kangaroo were to be compared to the species already present. It is reasonable to believe that the kangaroo would be in a similar location to the wallaby, as they both carry similar characteristics.
While sequence data can be very helpful in identifying relations between species, there are at least three other methods that can be used to determine evolutionary relationships as well. These can include environmental interaction, geographic location, and physical features. By evaluating the similarities between how species interact with their environment and the behaviors they exhibit, it can be understood that there is a possibility that the species are related, or have descended from a common ancestor. This possibility can also be explained through physical features, as parallels between a species' traits can explain connections to other species and a common ancestor. Geographic location can determine evolutionary relations, as relative location can express how a species, and others that are similar, interact with their environment and how they relate globally.
It is amazing to see how genetics relate to evolutionary theory, and how similarities in species can be examined.
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