In my biology class, we’re learning about gene regulation/expression and transcription of a gene.
I sort of understood what gene regulation is, but I still don’t understand the steps that go with the process and what transcription is along with what is the purpose of that. I also don’t understand the clear difference between needing mRNA to be synthesized through DNA?
I appreciate your help.
In: Biology
DNA is like a big library where all the instruction books needed to build your body are stored. The library doesn’t make things though, it just stores the books. In order to make things you need a factory and the factory needs a way to get books from the library so that it knows how to make things. The Cell Nucleus is the library and the Ribosoms are the factories. The go-between that gets books from the library to take to the factory is called [messengerRNA](https://en.wikipedia.org/wiki/Messenger_RNA) (mRNA). The Ribosoms also have another helper called transferRNA (tRNA) whose job it is to get the materials the factory needs to actually build the proteins. So mRNA transfers an instruction manual, and tRNA brings the necessary building blocks that match the instructions and the Ribosoms assemble them together to make proteins.
[Gene Regulation](https://www.khanacademy.org/science/biology/gene-regulation/gene-regulation-in-eukaryotes/a/overview-of-eukaryotic-gene-regulation) is how your cells decide what proteins to build. Your liver cells do very different things from your brain cells, how do they know what to do? The DNA in both cells is exactly the same!
You can think of gene expression like a librarian at the library locking up some books, and making others available to the mRNA. The librarian learns what books to make available based on messages she gets from outside the cell that tell her what sort of environment she is in. If the cell is surrounded by liver cells, for example, that cell librarian will also make her books available for building liver cell proteins and so the Ribosoms will build liver-cell proteins and not others.
It gets more complicated when we start to talk about how a cells “becomes” a certain kind of cell. I don’t know if your biology course has covered that yet. In short, if a cell divides from another mature cell it will usually be the same kind of cell because the Nucleus will inherit the cellular structure of the parent. So a liver cell will divide to produce another liver cell. However, there are also cells called “[stem](https://stemcells.nih.gov/info/basics/1.htm)” cells that have no “type” to them at birth. These cells can become any type of cell in your body, and they know what type to become from the environment where they find themselves. A stem cell in your brain that comes to rest near a dead neuron will likely turn into a new neuron, for example.
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