What is mitochondrial DNA?
Mitochondria often are referred to as the “powerhouses” of a cell. They break down sugar to produce chemical energy that powers many of the biochemical reactions a cell needs to function. Mitochondria have their own DNA, which is distinct from the DNA in the cell’s nucleus. The mitochondrial DNA – or genome – encodes only about 37 genes compared to the human genome in a cell’s nucleus, which contains about 23,000 genes. How is mitochondrial DNA passed on? Unlike a person’s nuclear genes, which are a mixture of genes passed down from that person’s mother and father, mitochondrial DNA is inherited solely from the mother in her eggs. Because of this maternal inheritance, there is no mixing of genes in offspring as happens with nuclear DNA. Therefore, it is possible to “trace” mitochondrial DNA back through many generations. Image provided courtesy of AXS Studio Inc. Artist’s rendition of a mitochondrion – its DNA is in its interior, beyond the folded inner membrane.
Although most DNA is packaged in chromosomes within the nucleus, mitochondria also have a small amount of their own DNA. This genetic material is known as mitochondrial DNA or mtDNA. Mitochondria (illustration) are structures within cells that convert the energy from food into a form that cells can use. Each cell contains hundreds to thousands of mitochondria, which are located in the fluid that surrounds the nucleus (the cytoplasm). Mitochondria produce energy through a process called oxidative phosphorylation. This process uses oxygen and simple sugars to create adenosine triphosphate (ATP), the cell’s main energy source. A set of enzyme complexes, designated as complexes I-V, carry out oxidative phosphorylation within mitochondria. In addition to energy production, mitochondria play a role in several other cellular activities. For example, mitochondria help regulate the self-destruction of cells (apoptosis).
Mitochondrial DNA are small loops of DNA found within organelles in the cell, mitochondria. Mitochondria serve as the “power plants” of the cell and are believed to be the descendants of ancient bacteria that participated so symbiotically with ancient cells that they became integrated into them as organelles. The vast majority of DNA in all animals is found in the nucleus, and is known as nuclear DNA, while mitochondrial DNA is the only DNA located outside of the nucleus. In contrast to the DNA in the nucleus, which contains about 20,000 protein-coding genes in over 3 billion base pairs, the mitochondrial DNA is relatively small, consisting of only 13 protein-coding genes in 15,000-17,000 base pairs. Unlike the nuclear DNA, which consists of linear DNA, mitochondrial DNA is found in the loop format, just like the DNA found in bacteria.
DNA (deoxyribonucleic acid) is the gigantic molecule which is used to encode genetic information for all life on Earth. DNA molecules consists of a long strand of base molecules arranged in the form of a double helix. The bases are adenine, guanine, cytosine, and thymine, often abbreviated as A, G, C, and T. What we ordinarily think of as “our” DNA, because it controls most aspects of our physical appearance, is also known as “nuclear DNA”, because every cell in our bodies contains two copies of it in the cell nucleus. Mitochondria (singular: mitochondrion) are small energy-producing organelles found in cells. Surprisingly, mitochondria have their own DNA molecules, entirely separate from our nuclear DNA. Most cells contain between 500 and 1000 copies of the mtDNA molecule, which makes it a lot easier to find and extract than nuclear DNA.
