DNA

DNA, or Deoxyribonucleic acid, is a molecule, a class of nucleic acids, named after the molecule contains deoxyribose. DNA is the main chemical component of chromosomes. DNA can constitute genetic instructions to guide biological development and vital functions. Its main function is long-term information storage, which can be likened to a "blueprint" for biological development and operation. DNA fragments with genetic information are called genes. Some other DNA sequences directly act on their own structure, and some are involved in regulating the performance of genetic information. In cells, DNA can be organized into a chromosomal structure, and the entire group of chromosomes is collectively referred to as the genome. Chromosomes replicate before the cell divides. This process is called DNA replication. In the process of division, the parents copy and transfer a part of their own DNA (usually half, that is, one of the DNA double strands) to the offspring, thereby completing the propagation of the trait. DNA exists in the nucleus, mitochondria, and chloroplasts, and it can also exist in the cytoplasm of some cells in a free state. DNA is also found in most known phages, some animal viruses, and a few plant viruses. For eukaryotes, such as animals, plants, and fungi, chromosomes are stored in the nucleus of cells; for prokaryotes, such as bacteria, they are stored in the nucleus in the cytoplasm. Chromatin proteins on the chromosome, such as tissue proteins, can organize and compress DNA to help DNA interact with other proteins and regulate gene transcription.