Biology#37

Genetic Mutation

Info

日期：2024年4月3日 课程链接：Is drinking milk a Superpower? Genetic Mutations: Crash Course Biology #37

• 信息1：Genetic changes can be helpful, harmful, or just neutral.
• 信息2：You see, DNA contains sequences of nucleotide bases, and each base is represented by a particular letter: A, T, G, or C.
• 信息3：A mutation occurs when the letters in DNA are altered. This can sometimes change the protein that that section of DNA codes for, the way a new ingredient can totally change a dish — like if you accidentally added sugar instead of salt. But mutations can also happen in DNA that doesn’t code for proteins. These mutations occur quite often with no real effect — kind of like the garnish on your plate.
• 信息4：Mutation can be caused by many factors, like error during DNA replication, mutagen, inherited mutations, etc.
• 信息5：So, where a mutation occurs in the body is going to help determine its impact.

• 信息6：One common reason for how mutation alter DNA is substitution, where one nucleotide is substituted for a different one.

  Substitution可以被分为四类，①missense mutation, 比如GAA告诉细胞形成谷氨酸，如果这时GAA变异成了GUA，细胞会形成缬氨酸——一种和谷氨酸功能不一样的氨基酸。②nonsense mutation，比如GAA告诉细胞形成谷氨酸，如果这是GAA编译成了UAA，而UAA是stop codon（终止密码子），它会告诉细胞蛋白质已经构建完成了。And this can stop production, resulting in a fragment rather than a complete protein. ③silent mutation，比如GAA变异成了GAG，但GAG和GAA一样，告诉细胞形成谷氨酸，看似没有任何区别，但2022年对酵母菌的一项研究发现，这种silent mutation对酵母菌繁殖似乎有一定影响，Until, in 2022, a study on yeast found that these mutations still hurt the yeast’s ability to reproduce in more than 75 percent of cases. Even if silent mutations weren’t changing the molecules in a protein, they were affecting when and how often proteins were made. ④frameshift mutation，碱基的增减。

• 信息7：In 2020, scientists Emmanuelle Charpentier and Jennifer Doudna won the Nobel Prize in Chemistry for figuring out how to harness that powerful immune system into a gene-editing tool called CRISPR/Cas9.