Mitochondrial DNA: What is Mitochondrial Deoxyribonucleic Acid? Function and Mutations

Our body, everybody, every living being, is made of cells, just as a building is made of bricks.

Human beings have many millions of cells, somewhere around ten trillion.

Each cell contains a nucleus surrounded by cytoplasm, which is enclosed in a cell membrane.

The cytoplasm contains various organelles, such as mitochondria, which are tiny power plants in our body, and lysosomes, the “waste-processing plants” in our cells.

The nucleus contains nuclear deoxyribonucleic acid, and the mitochondria contain mitochondrial deoxyribonucleic acid.

Deoxyribonucleic acid stores the programming code that determines the structure and function of our bodies.

The DNA code is different for all living things, except identical twins.


People from the same family usually share a series of characteristics: their eye or hair color, physical constitution, level of intelligence, and susceptibility to particular diseases, among others.

In short, although each person’s genome looks almost identical, there are slight differences that make each of us unique.

These are also what make us similar (in some way) to our blood relatives since we share specific characteristics.

These small but specific DNA mutations that can occur in indifferent members of the same family allow us to trace some inherited diseases with great precision.

Genetics is the science that studies the genetic identity card of a human being and establishes how genetic transmission occurs.

Although, in practice,’ genetics ‘ is often used synonymously with ‘inherited,’ genetic changes can also occur during embryonic development or later in life.

In other words, we can develop mutations that we have not inherited and that we do not always pass on to our children.

These “somatic” mutations are also studied, but they are not part of classical genetics or the study of heredity.

In 2003, geneticists managed, through the ‘Human Genome Project,’ to map the precise sequence of the more than three billion nucleotides that make up our DNA. Therefore, we can say that we know the composition of the human genome.

Genes located on this long chain are well-defined DNA pieces responsible for the synthesis or “code” of a particular protein.

If DNA is the complete programming language of the human organism, we can see genes as specific commands.

Thanks to the discovery of the human genome, we now know the basic package of the genetic information stored in our cells.

This is important because these minor differences (repetitions, omissions, or substitutions) within the basic package determine how we are or how we function. We create the differences between people or the similarities between blood relatives.

However, it would be an exaggeration to say that our DNA code is an open book for geneticists.

Research continues on the precise number of genes and the DNA between them, how they work, and how they interact.

Mitochondrial deoxyribonucleic acid

Mitochondrial DNA is found in the cytoplasm of cells, specifically in the mitochondria.

These are a particular type of cell organelle, and there are about 100 to 1,000 of them in each cell.

They are also known as small power plants because they convert sugars and fats into energy (adenosine triphosphate) necessary for our body to function correctly.

We only receive mitochondrial DNA from our mother; the father’s mitochondrial DNA is lost during fertilization because it is broken down.

The egg provides the cytoplasm, and this contains the mother’s mitochondria.

Mitochondrial DNA is ring-shaped and therefore not organized into chromosomes.

It represents less than one percent of the total amount of DNA, with only 16,500 nucleotides, compared to three billion in nuclear DNA.

However, the several hundred mitochondria in each cell contain these circular strands of DNA, which have 37 active genes.

THEREFORE, mitochondrial DNA is crucial for our metabolism, and if there is any defect in its structure, it can lead to complex disorders.


Although most deoxyribonucleic acid (DNA) is packaged on chromosomes within the nucleus, mitochondria also have a small amount of their DNA.

This genetic material is known as mitochondrial DNA.

Mitochondria are structures within cells that convert energy from food into a form that cells can use.

Each cell contains hundreds to thousands of mitochondria found 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 primary energy source.

A set of enzyme complexes carry out oxidative phosphorylation within the mitochondria.

In addition to energy production, mitochondria play a role in many other cellular activities. For example, mitochondria help regulate the self-destruction of cells (apoptosis).

They are also necessary for producing substances such as cholesterol and heme (a component of hemoglobin, the molecule that carries oxygen in the blood).

Mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function.

Thirteen of these genes provide instructions for making enzymes participate in oxidative phosphorylation.

The remaining genes provide instructions for creating molecules called transfer RNA (tRNA) and ribosomal RNA (rRNA); these types of RNA help assemble building blocks of proteins (amino acids) into functional proteins.


Heteroplasmic mutations of mitochondrial DNA are an essential source of human disease.

The mechanisms governing heteroplasmic mtDNA mutations’ transmission, segregation, and complementation are unknown.

But they depend on the nature and dynamics of the mitochondrial compartment and the intramitochondrial organization and mobility of mitochondrial DNA.