Hello! Mysterious person, I'm Emily. Oh wait, you already knew that, silly me. Welcome to my blog, if you've never seen it before. It's called, "Em Fu The Science Guru!" Get it, like Bill Nye the Science Guy? I know what you're thinking, I'm a loser. But the truth is, I was trying to be creative, and at the time, it seemed like a catchy name. To be honest, I still really like it, no matter what anyone else says. After you read my blog post, you can check out my fishy (you can feed them!), or my scientific links, or my favorite scientific quote, if you'd like. But that's optional, you can if you have free time. So I think that's enough of an introduction to my blog. Now I will actually begin with the biology, sigh. I'll try to make this as entertaining as I can for you.
So the title to this chapter is "Mutation, DNA Repair, and Cancer." Not too many know this, but I'm fascinated by cancer, and might even pursue oncology one day. Also, I love blood! No, not in a creepy vampire kind of way, but in a biological way. Learning about blood was one of my favorite parts of A&P, I found it really cool. Hematology and oncology are closely related, most doctors who pursue one of these specialities end up specializing in both. It's kind of like the relationship between Gynecology and Obstetrics. Most of the doctors in this field are OBGYNs. I would love to study hematology further, but most likely this would also involve going into oncology. Luckily, I have a great interest in oncology, and actually enjoyed this chapter.
Heading back to biology, the first section was all about mutations. Mutations are often associated with cancer, and are often seen as bad. However, mutations are a natural part of life, and contribute to evolution. So they can be good, and are actually necessary for a species to survive. There are a few different types of mutations, all causing different effects of polypeptides. It's super easy to get them confused, but I found Table 14.1 in the book to be really helpful. I'd suggest checking it out for quick review before an exam. Just so you know, this isn't one of my official useful materials. I just wanted to mention it, so you could check it out if you hadn't before.
The mutation type that fascinated me the most were frameshift mutations. They produce a completely different amino acid sequence because the reading frame is shifted over, changing the entire sequence downstream. When reading the book, I literally said, "whoa!," aloud. It's amazing how one addition/deletion of a single base can do so much. I decided to look into frameshift mutations as one of my useful materials. This article is titled, "Immunogenic peptides generated by frameshift mutations in DNA mismatch repair-deficient cancer cells." The authors wrote it in a very clear manner, unlike some PubMed articles that are impossible to comprehend. I'm sure you know what I'm talking about. The article states that the loss of DNA mismatch repair functions contribute to approximately 15% of human tumors. In cancer cells, there's an insertion or deletion at microsatellites. Microsatellites are repeating sequences of base pairs of DNA. Any mutations in coding microsatellites can be very bad, because genes can lose their function! Oh no! Frameshift mutations like these have been found recently. The authors found a "broad but comprehensive set of frameshift peptides that might be combined in a multivalent vaccine for MSI+ cancers." MSI stands for microsatellite instability, in case you were wondering. They identified and examined mutations in different genes, and found mutations that seemed similar to those found in cancer. Their research hopefully has brought us closer to finding a vaccine to MSI cancers. MSI cancers seem really interesting, and they connect frameshift mutations back to real-life. This article proved that frameshift mutations are incredibly dangerous and make a big difference.
After learning all about the consequences of mutations, I realized how vital DNA repair was! DNA repair allows us to live our lives by minimizing the occurence of mutations. One type of DNA repair is nucleotide excision repair (NER). I didn't understand it at first because the book's definition was a long run on sentence. After reading it a few times I understood it, but couldn't exactly picture it in my head. So I looked it up and found this diagram that does a pretty good job of illustrating all of the information. The book also had a diagram (showing NER in E. coli), but I understood this one a lot better. The illustrations could be better, but the point got across well. First, the damaged DNA gets distorted. Then, an enzyme complex finds the distortion and separate the DNA. Single-stranded binding proteins help to stabilize the strands and both sides are cleaved by an enzyme. Lastly, the damaged part is taken away and the empty space is filled by DNAP and sealed by DNA ligase. This diagram helped me realize that NER is actually quite simple after all!
The last section of the book was all about cancer! One topic I found quite interesting were types of cancer caused by viruses. The book specifically talked about the Rous sarcoma virus (RSV), and I decided to look more into it. This article gave a detailed description of RSV. RSV was the first virus shown to be able to cause cancer, called an oncogenic virus. A tumor from this virus is called a sarcoma, which is a connective tissue tumor. It's considered to be a retrovirus, it's genes are encoded in RNA instead of DNA, like HIV. RSV has four genes: gag encodes the capsid protein, pol encodes the reverse transcriptase protein, env encodes the envelope protein, and src which encodes a tyrosine kinase. Src is what makes RSV oncogenic, although it is not understood very well. As the article states, "the expression of this gene in some way...is able to transform cells in culture." A study was conducted on cells infected with RSV and it was found that they are temperature-sensitive, meaning that temperature changes can activate or denature the encoded protein, reversibly. In addition to it being a viral gene, it is also a proto-oncogene, called c-src. This is found in vertebrates and invertebrates, including humans! Ours in on chromosome 20, by the way. C-src has probably not changed much since the start of evolution because of how widely its found. Fortunately, Peyton Rous, the man who discovered RSV was awarded a nobel prize for his work, at the age of 87.
Thanks so much for reading by blog! I apologize for the length, but I hope you enjoyed reading it!
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