Historical background

Cells are the basic building blocks of all living organisms. Our body is composed of trillions of cells. Each of these cells contains deoxyribonucleic acid (DNA), the hereditary material. DNA contains genetic instructions and tells the cell what to do and how to grow. DNA is stored in chromosomes. Humans have 23 pairs of chromosomes- a total of 46- and each pair is labeled with its own number or letter for the X and Y sex chromosomes. Each set of chromosomes comes from each of our parents. Genes are located on chromosomes and determine our physical features. Genes are made up of DNA and they make molecules called proteins, the building blocks of all structures in the body