Together, a base, sugar, and phosphate are called a nucleotide. Each base is also attached to a sugar molecule and a phosphate molecule. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.ĭNA bases pair up with each other, A with T and C with G, to form units called base pairs. Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Mitochondria are structures within cells that convert the energy from food into a form that cells can use. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA). Nearly every cell in a person’s body has the same DNA. Much research is being conducted on noncoding DNA.Ĭoding DNA is responsible for harboring the specific DNA sequences that encode instructions for making proteins.DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Noncoding DNA also provides chromosomal structure and binding sites for regulatory proteins. The regulatory function of this DNA is to determine when and where some genes are transcribed. This type of DNA is now referred to as regulatory DNA. Noncoding DNA typically refers to any DNA that does not code for a protein. However, noncoding DNA does have a purpose. Noncoding DNA is sometimes referred to as junk DNA. Mitochondrial DNA replicates separately from the rest of the cell and is passed down only from the mother. Mitochondrial DNA has one chromosome that codes for the specific proteins needed for the metabolic processes that mitochondria perform. Mitochondria contain their own DNA called mitochondrial DNA. For more information on chromosomes, see section “What are Chromosomes?"Īs noted in the section “What are Eukaryotic Cells?”, mitochondria are organelles that are responsible for the cell’s energy production. Autosomal DNA is passed down from both the mother and the father and provides clues to a person’s ancestry. In each pair of autosomes, one was inherited from the mother and one was inherited from the father. Autosomal DNA (also called nuclear DNA) is packaged into 22 paired chromosomes. There are two types of DNA in the cell – autosomal DNA and mitochondrial DNA. Nucleotides are the building blocks of nucleic acids. The middle rungs are formed by the base pairs (and the hydrogen bond). The sides of the ladder consist of sugar and phosphate molecules. The nucleotide strands form a spiral double helix that looks similar to a ladder. Nucleotides are arranged in two long strands and are held together by the sugar-phosphate backbone. One base plus a deoxyribose sugar molecule and a phosphate group create a nucleotide. The base pairs are held together by a hydrogen bond. For details on the human genome, see section “What is a Genome?” DNA composition and structure Only about 2% of the entire human genome (complete set of genetic information for a person) consists of genes. Genes serve as the blueprint for the production of proteins. Genes, the basic physical and functional units of heredity, are composed of DNA sequences. The side-by-side arrangement of bases in a particular sequence, unique to each human (or other organism), spells out the exact instructions needed to create that person and also gives the person his or her unique phenotype or traits (distinguishing characteristics). For more information on chromosomes, see the section “What are Chromosomes?”ĭNA is made up of four chemical (nitrogen) bases: If extended, the DNA would measure approximately 2 meters. Chromosomes consist of DNA coiled around histones (alkaline proteins). DNA is mostly located within chromosomes in the nucleus, but some DNA is also found in the mitochondria. The same DNA is located in nearly every cell of the human body. DNA is passed from generation to generation in humans and many other organisms. Deoxyribonucleic acid (DNA) is the cell’s hereditary material and contains instructions for development, growth and reproduction.
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