Ok, so the DNA has the instructions on how to build a specific living thing right? But the DNA is just a molecule. It doesn’t form a living organism on its own. So, how does the DNA tell the cells what kind of cell to be and how to build organs? How does the body “reads” the DNA to know what to do and how to do it? It’s a question I always had.
In: Biology
The answer to your questions is very complicated. The entire field of genetics essentially exists to answer your question. As Emyrssentry said in their answer, what’s coded into the DNA is the recipe for making thousands of different kinds of proteins, and these proteins are what perform the vast number of things the cell needs to do. A gene is the term used for the region of DNA that contains the code for a specific protein. The regulation of these genes, in other words controlling whether they are “on”, meaning that protein will be made, or “off”, meaning it won’t be made (or finer regulation like whether a lot or a little of the protein is made) is the key to your questions, and something that is still in the process of being discovered and understood by biologists. What makes a skin cell different from a brain cell is which genes are active and which are turned off.
>How does the body “reads” the DNA to know what to do and how to do it?
This question can be answered more directly. You may have heard that DNA contains 4 “letters”: A, C, T, and G. The proteins that are ultimately created from “reading” are chains of molecules called amino acids, and there are 20 of them (we’ll say 20 to keep things simple, don’t @ me biologists, I know it’s not entirely true). There is a “genetic code” that is basically a mapping of 3 letter DNA sequences to amino acids, so AAG codes for Lysine, for example. The cell copies a region of DNA to an mRNA, and then there are molecules called tRNA (transfer RNAs) that are in the cell which are carrying the different amino acids, and bind to the specific three-letter code for the amino acid they’re carrying. So a tRNA will bind to the AAG of an mRNA, and be holding a Lysine amino acid. Other tRNAs will bind to different three letters of that same mRNA with different amino acids, and so the amino acids will all be lined up and connected to form a protein. That’s a very simplified explanation of how it happens, and there are some inaccuracies I did on purpose to keep it simple, but it gives you the basic concept of how it works.
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