Ribosomes create proteins, and the order of amino acids in proteins is determined by DNA informal and mRNA molecules.
mRNA molecules are interface molecules that connect the ribosome's protein synthesis process with DNA's amino acid order arrangements.
Also, mRNA molecules are created by some enzymes that interact with DNA in the nucleus, and the process of mRNA synthesis is regulated by some regulator molecules or directly by the mRNA polymerase enzyme (the enzyme that makes mRNAs).
In general, if the cell requires a protein molecule, the regulator molecules that interact with DNA or the RNA polymerase enzyme will be activated, but if there is no need for a protein, the regulator molecules that interact with DNA.
The regulator molecules are then inactivated, or our enzyme is inactive, and thus will not process to make mRNA and thus proteins, resulting in cell proteins being balanced in an amazing procedure. (There are differences in the regulation of mRNA synthesis between prokaryotes and eukaryotes, but the general procedure is the same.)