Without DNA, life would not be able to perpetuate itself. DNA is needed as it is the blueprint of life. Every species of plants and animals contains a genetic substance called DNA that passes on the physical characteristics of an organism from one generation to the next.
DNA contains all information that tells a cell how to grow, elongate, and form tissues, organs and organ systems. DNA, which stands for deoxyribonucleic acid, is found in every living cell. Each cell contains a nucleus at the center; within the nucleus, there are a specific number of chromosomes. Every species has a fixed number of pairs of chromosomes. For instance, humans have 23 pairs of chromosomes.
A chromosome has three sections with a central portion called the centromere. The two ends of the chromosomes attached to the centromere are called chromatids. Inside the chromatids are strands of DNA.
DNA consists of a double helix or a double chain of nucleic acids that are coiled around like a spiral staircase. The four subunits, or nucleotides of human DNA are adenine, guanine, thymine and cytosine. These form genes that are the basis of various characteristics or physical traits. These four nucleotides are paired differently along the entire length of the DNA, giving rise to genes.