Nucleus

At the heart of every cell is its control center, called the nucleus. Inside the nucleus are forty-six threadlike structures known as chromosomes, and each one of these structures contains thousands of genes. Chromosomes and genes are made of deoxyribonucleic acid, or DNA, which transfers the heredity material from generation to generation. The DNA of which each gene is composed contains a genetic message, or blueprint for manufacturing one of the many proteins that make up the human body and keep it running.