In Biology, we just finished our genetics and inheritance unit, which was REALLY cool. We got to learn how about DNA, the cell, and different types of inheritance. I personally thought that learning about how DNA is the code for proteins was the coolest part of our entire unit, because I had always wondered how traits were expressed in different people and I could never wrap my head around how such a small thing could hold all of the information for an entire body. We started our unit by watching Twitch, a documentary about a teenagers struggle behind wanting to know if she had Huntington's Disease, a genetic disorder, or not. It was incredibly interesting, and it sparked many questions about how genetic disorders are inherited, or what a genetic disease was in the first place. With these questions, we moved into our unit. Now that we are done with our genetics unit, we looked back to our questions and tried our best to answer them. P.S. If you want to know more about Twitch, you can scroll down to the article I wrote about it at the beginning of our genetics unit! Answers to my questions about the twitch documentary: How many mutations (or how long) is the gene that contains Huntington's Disease? The mutation for Huntington’s Disease occurs in the HTT gene, which codes for a protein called huntingtin. It’s cause is a segment of DNA, specifically CAG, repeating many times in the gene. While unaffected people typically have this segment of DNA in their HTT gene about 10-35 times, people with Huntington’s have the CAG segment 36-120 times. This results in an elongated huntingtin protein that then breaks up into smaller, toxic pieces that bind together and accumulate in neurons, disrupting their functions. How do genetic diseases first occur? A mutation occurs in an individual's gametes, and they pass down that mutation to their offspring. Mutations are errors that DNA polymerase made, affecting the tertiary structure of the proteins that it codes for. There are two different types of mutations (BASICALLY) which are point mutations, where only one nucleotide base is changed, and frameshift mutations, where extra nucleotide bases are added, causing a shift in the rest of the DNA strand. A mutation can either be dominant, meaning that it only needs one allele to be expressed, or recessive, meaning that it needs to be homozygous for an allele for it to be expressed. If the mutation is recessive, or if it only affects individuals after child rearing age, it will most likely be passed down through generations and more people will begin to suffer from it. Is it possible (or will it be possible) to cure genetic diseases with genetic modification? If so, what would those missing genes be replaced with? Most likely. Genetics and genetic engineering are fields that are exploding right now. Scientific discoveries are revealing more and more about what we can do now and what we might be able to do. As for what genes might replace genetic disorders, that’s an ethical decision that will have to be sorted out in the maybe not so distant future. Are there genetic diseases that are a dominant trait? Yep. Huntington’s is actually one of them. For a dominant genetic disorder to recur though, it has to either affect a person after they’ve had kids, or it has to be insignificant enough that it can’t prevent a person's reproduction. Dominant genetic disorders are typically rarer than recessive genetic disorders because dominant genetic disorders can’t hide in individuals, meaning everyone that gets the mutated allele will suffer from the disease, usually preventing them having offspring. Are genetic diseases usually more present in certain regions (where they probably originated)? Yes. A way that genetic disorders can be determined is looking at the history of a family and where that family originated from. A cool activity that we did this unit was when we were given a description of a disorder but we weren’t told what that disorder was. Our class had to try and figure out what the disease was, and the most helpful bit of information was that the trait was more common in eastern europe. We were able to find out that the disease was Tay-Sachs Disease, a recessive genetic disorder that results in the premature death of infants. Sources: “FAQ About Genetic Disorders.” National Human Genome Research Institute (NHGRI), USA Government, 10 Nov. 2015, www.genome.gov/19016930/faq-about-genetic-disorders/. Mayo Clinic Staff. “Huntington's Disease.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 16 May 2018, www.mayoclinic.org/diseases-conditions/huntingtons-disease/symptoms-causes/syc-20356117. “What Is a Gene Mutation and How Do Mutations Occur? - Genetics Home Reference - NIH.” Genetics Home Reference, National Institutes of Health, 29 Jan. 2019, ghr.nlm.nih.gov/primer/mutationsanddisorders/genemutation.
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