The DNA is in the cells. Depending on whether it is simple or complex organisms, it can be located in the nucleus or in the mitochondria. DNA is a molecule called deoxyribonucleic acid, with the biological instructions for each species to be unique.
DNA imparts the instructions that are activated during reproduction. In this way cats beget cats, dogs beget dogs, and humans beget humans. The human body has between 50 and 100 trillion cells. These cells are organized into tissues, skin, muscles, and bones.
Each of these cells contains the body's genetic instructions stored in its DNA. However, each cell uses only part of the DNA instructions: the one it needs.
For example, muscle cells use DNA that specifies the muscle apparatus, while nerve cells use DNA for the nervous system. It is as if each of the cells reads the part of the instruction manual that it needs.
Types of DNA according to its location
DNA is found in the nucleus and also in the mitochondria.
Nuclear DNA
DNA is in an area with different compartments within the cell called the nucleus. This occurs in organisms called eukaryotes.
This cell is very small and each eukaryotic organism has many cells that compose it.
Because of this, the DNA cell is coated with a very special coating called a chromosome.
In the process of DNA replication, it unwinds in order to be replicated. In other stages of the cell cycle, some parts of the DNA also unwind.
This unwinding occurs to give instructions to the body about the different processes that must be carried out. One of the processes is the manufacture of proteins.
During cell division, DNA remains in its compact chromosome form so that it can be transferred to new cells.
Mitochondrial DNA
In complex organisms such as humans, mammals in general, and others, DNA is found in other structures as well.
A small amount of DNA can be found in additional cell structures called mitochondria.
Mitochondria are the engine of cells, since they manufacture the energy they need to function.
Organisms that come from a father and mother obtain their nuclear DNA from both. Half of the DNA is from the mother and the other half is from the father.
But the mitochondrial DNA is inherited only from the mother, because only the ovules support the mitochondria in fertilization.
Chromosomes
Each DNA molecule is assembled like a chromosome. Humans have two sets of 23 chromosomes in each cell, inherited from each of their parents.
A human cell, therefore, contains 46 chromosomal DNA molecules.
The genes
Each DNA molecule that makes up a chromosome can be viewed as a set of shorter DNA sequences.
These are the units of function of DNA, called genes. Each gene guides the production of a particular component of an organism.
References
- Joshua Bush (2017) Where is the DNA housed in a Cell? 11/16/2017. Sciencing. sciencing.com
- Editor (2014) Where is DNA found? 11/16/2017. Putting DNA to Work. koshland-science-museum.org
- US National Library of Medicine (2017) What is DNA? 11/16/2017. Genetics Home Reference. ghr.nlm.nih.gov
- Molecular Biology of the Cell, 5th Edition; Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, Peter Walter. 11/16/2017. onlinelibrary.wiley.com
- Editor (2015) Deoxyribonuclic Acid (DNA). 11/16/2017. National Human Genome Research Institute. genome.gov