Cell Biology 101: What is a Gene Mutation?

You may have noticed the latest research on Wuhan pneumonia by the Hong Kong Polytechnic University, which found that 90% of early Hong Kong patients were found to have the "G251V" gene mutation in the Wuhan pneumonia virus; on the contrary, the "P314L" gene common in Europe and America Mutations were not found. Readers who haven't read high school biology may be confused. Let me briefly explain what G251V and P314L are.

To understand these two "codes", we must first understand a little bit about what the genetic code is and its structure.

The genetic properties of all organisms and viruses are documented in the familiar form of DNA (or RNA). There are many different genes (Gene) on DNA, and each gene is composed of a series of nucleotides (Nucleotides). There are four main types of nucleotides in the human body, namely A, T, C, and G. The order and length of these nucleotides affect the properties of the proteins that each gene can make.

To make it easier to understand a series of biological terms, DNA can be compared to a book, and genes are individual chapters in the book. The language used to write this book is unique to cells, and this "cellular language" has only four letters, namely A, T, C, G. Every three letters make up a word, and a series of words can be read together to understand the meaning of each individual chapter. For example, here is a hypothetical gene consisting of three words that exists on DNA:

(Chapter before DNA)…CAT-ACT-TGT…(Chapter after DNA)

But this kind of cell language is basically unreadable, and it needs to be translated into a language that the outside world can understand to express the meaning (Expression). At the same time, because the book DNA itself is too heavy and redundant, it is impossible to translate it at one time. Therefore, before translation, each chapter needs to be independently transcribed (Transcription), which is called mRNA. as follows:

CAT-ACT-TGT

Translators would then translate these transcripts into a language understood by the outside world: proteins. Protein is composed of a series of amino acids (there are 20 kinds in the human body), and each cell word (ie genetic code, Genetic codes) is exactly representing an amino acid. The mRNA above will be translated into:

H -T- C (the translation comparison table will be found by Google, no need to memorize it)

Once the H, T and C protein is successfully translated, it can perform its function inside or outside the cell. But of course, normal proteins are much longer and more complex than this fantasy, and I have largely omitted the process.

Back to the topic of mutation. The so-called genetic mutation is that a certain word on a certain chapter (gene) is changed for no reason. Such abrupt changes, if not corrected before transcribing, can lead to a change in the meaning of the translated protein.

For example, if the above fantasy gene has the following changes:

CAT-ACT-T G T --> CAT-ACT-T A T

After translation, it becomes a protein like this, which changes its function:

H-T- C --> H-T- Y

For the convenience of expression, biologists will call the above gene mutation C3Y, that is, "the amino acid C in the third sequence becomes the amino acid Y".

By analogy, G251V and P314L mentioned in PolyU's research represent that "the 251st amino acid G becomes the amino acid V" and "the 314th amino acid P becomes the amino acid L". But it should be noted that these two gene mutations actually occur in two genes of Wuhan pneumonia virus, P314L occurs in the gene Orf1b, and G251V occurs in ORF3a, that is, these two gene mutations actually affect different proteins. Function.

For an in-depth understanding of the process of gene transcription and translation, you can take a look at Moderna's introduction: https://www.modernatx.com/mrna-technology/science-and-fundamentals-mrna-technology

PS The high mortality rate in Europe and the United States is caused by many factors (such as the number of elderly patients), which may not be directly related to the gene mutation P314L.