For example why is the protein for hair only made in your head? not on your eyes or your lips.
In: 1
What you’re asking about is called cellular differentiation. It’s what makes a liver cell a lover cell and not a skin cell or a lung cell. Differentiation happens during embryonic development, when you were little more than a cluster of a few dozen cells. The explanation of how differentiation happens is a pretty complex, and is beyond ELI5, but basically signals like orientation (gravity top vs bottom) and surrounding cells start the process.
As you alluded to in your question, every cell has the same DNA, and thus can technically make all the same proteins that every other cell makes. This processes is called transcription (reading the DNA and making an mRNA copy of it) and translation (reading the mRNA and making a protein from it). Once a particular gene becomes transcriptionaly active it remains active (to some degree). It’s a positive feedback loop, which is common in biochemistry. The more often a gene is transcribed, the easier it becomes to transcribe it in the future. This helps ensure that skin cells stay skin cells and don’t start making liver cell bile.
Your cells can “check” that they are properly differentiated from signals they receive from surrounding cells. If they aren’t getting a “you’re a skin cell” signal, they will trigger apoptosis, which means they kill themselves. Cells that don’t respond to these extracellular signals are called cancer.
Latest Answers