In order to make protein your cells need to replicate DNA. This process is called DNA replication. (Pretty straight forward). Enzymes go down the DNA double helix and break apart the hydrogen bonds that hold the DNA together. Then as the DNA double helix unravels itself the complimentary hydrogen bonds come and link themselves to their compliments.

Then once the hydrogen bonds link to their compliments that two original strands become 4 strands, two in each double helix. At the end of the process you have two double helixes that are exactly the same and just to be clear they are no longer connected.

How does this keep me alive? The DNA has to be replicated for you to keep regenerating cells to replace the cells that die over a period of time. As each cell divides to make new cells the DNA has to be replicated so that each cell can have its own set of instructions.

If you don’t have this process you wouldn’t even survive being a zygote.