Introduction
As a follow up to our group's work at determining the lineage of an ancient reptilian bird, which was completed last week, this week each member of the lab group was tasked with BLASTing a human gene coding for some sort of protein and then discovering the similarity of that gene to genes of other closely related organisms. For my experiment, I decided to BLAST human keratin, an important gene for human structures like hair and nails. My initial prediction for this gene was that it would be closely related to other keratin genes of mammals because other mammals, from dogs to rhinos, have keratin based structures like hair. I did not think that other organisms outside of the mammal family would have this gene because snakes or fish or worms do not have hair or nails as mammals do.
Procedure
After picking my gene of interest, I began by going onto the BLAST Entrez Gene website to search for the particular gene that I would use for this investigation. I entered "human keratin" into the search box at the top of the webpage and pressed enter. From there I was taken to a results page on which many different types of human keratin were displayed, shown below.
I was not sure which keratin gene to pick because I did not know that humans had that many types of keratin in their bodies. In the end I decided to choose Keratin 18 for two reasons. First and foremost, it was top of the search list so perhaps it is more keratin-y than other keratin genes. Secondly, and most importantly, 18 is my lucky number so I thought I would have a better chance of producing a good experiment with the number 18.
Clicking on the Keratin 18 link, I was taken to the homepage for keratin 18 with many different pieces of information. this is shown below. I needed to figure out the actual nucleotide sequence of keratin so that I could BLAST it, so I scrolled down to the section labeled "mRNA and Proteins" and clicked on the first link as the lab manual instructs.
From there I was taken to another page full of information, but I clicked the link labeled "FASTA" to find the actual nucleotide sequence. The link too me to the sequence, which is pictured below once again.
I then copied and pasted the sequence into the BLAST search page, labeled it "Human Keratin", and selected the option to check the gene against both similar and dissimilar genes from other organisms. I did this so that I could gather more results and have a more well-rounded report. From there I BLASTed the gene and waited for my results to come back.
Results
After BLASTing my gene, I was met with a long page of results from my search, and I have included a screenshot of the top few results.
Looking at these results, I see that my predictions were, for the most part, quite true. as expected, the Keratin 18 gene is extremely similar to other Homo sapien genes, but it is also strikingly similar to Keratin 18 genes of different organisms such as the Gorilla gorilla, the Western gorilla, or the Pan trogolodytes, the common Chimpanzee.
Other results that I received, such as similarity to the Papio anubis or the Macaca mullata, were also quite predictable because both of these organisms are primates, being the Olive Baboon and the Rhesus Macaque respectively. In fact, all of the results that I obtained that were displayed on the first age of results, or the first 100 results, were all similar primates. Therefore, one can obviously conclude that humans are descended from primates, but also that Keratin 18 is an extremely common form of Keratin found in many different primates.One can also conclude that the gene for Keratin 18 is extremely unique to primates because it is not found in other organisms such as dogs or rhinos, as I had previously hypothesized.
Perhaps I did not see any matches for organisms other than primates simply because there were so many matches to Keratin 18 that they could not be displayed in the 100 results that I was given. If BLAST gave more results, I bet that I could find a similar gene in a non-primate, but perhaps this gene would be more dissimilar to Keratin 18 in humans than it is similar.
Thoughts
I think that it would be beneficial to an analysis of the BLAST tool that we have used for the past two weeks, as well as to the concept of evolution as a whole, to answer a question posed by Mr. Wong in his assignment. The question is: "Does the use of DNA in the study of evolutionary relationships mean that other characteristics are unimportant in such studies?"
I do not think that DNA should be the be-all end-all when it comes to evolutionary relationships. I think that many different factors must be taken into account, such as morphology and environmental factors. I think that, although DNA can provide substantial support for relationships between many organisms, it is not foolproof. For example, there could be an organism on an island in the middle of the Pacific that evolves a certain gene that is beneficial to survival. On another island in the middle of the Atlantic, another organism develops an extremely similar gene because it is faced with the same environmental conditions as the organism in the Pacific. Though these genes might be extremely closely related, even up to 99%, it is possible for two genes in two separate organisms that are completely unrelated to develop similarly. Though the odds of this occurring are so infinitesimally slim, it is still possible.
No comments:
Post a Comment