Describe how the chromosomes can control all the metabolic activities of a cell.
The chromosomes consist of protein and the most basic units of heredity, the genes, which are composed of DNA. The nucleotide sequences of the genes' DNA contains the information that determines the nature of the cell during differentiation and that controls the metabolic activities of the cell. The genes exert such control by directing the synthesis of the enzymes that regulate all the cell's biochemical reactions, by directing the synthesis of structural proteins. But since DNA never leaves the nucleus and since proteins (including enzymes) are synthesized in the cytoplasm, a messenger, called messenger RNA (mRNA), is needed to go from the nucleus to the ribosomes, the sites of protein synthesis in the cytoplasm. The mRNA transcribes the DNA's nucleotide sequences, leaves the nucleus, travels to the ribosomes, and acts as the model for the ordering of amino acids during protein formation.
